LPC quad UART garbling 8th bit in TX data - difficult to rep

[Frantisek.Rysanek@post.cz]

Dear Everyone,

apologies for cross-posting, I'm wondering if some of the veterans of
10-15 years ago are still reading these USENET groups...
I'm sending this problem description just in case the weird symptoms
ring a bell with someone - if someone happens to have a past
experience that might resemble my symptoms.
I will deliberately not name the vendors involved - we are not sure
exactly where the problem is.

Strange as it may seem to the majority PC user nowadays, in our
industrial process control practice we're still using RS232 and its
flavours RS485, RS422. The problem at hand occurs in a [brand
censored] panel PC (that's an LCD with an embedded motherboard in a
flat wallmount box), that's based on an Intel Atom, coupled with the
i945GSE chipset (including some ICH7 flavour for a south bridge). The
PC doesn't seem to contain a full-fledged SuperIO chip (no floppy, no
PS2, no LPT/joystick, just USB) and its three serial ports are
implemented using a [brand censored] quad UART chip, that connects to
the ICH via an LPC bus. The quad UART chip has some configurable
"industrial" features, such as TEMT bit exported to an outer modem
control signal (for HW-based RS485 RX/TX steering) and something
called "9bit mode".

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.
In HyperTerminal, it looks like a string of good characters mixed with
non-ascii garbage. An interesting feature seems to be, that it does
this with *any* character you can type on the keyboard - any letters
or numbers. If you type different characters in a sequence, the
garbage doesn't occur. If you keep sending a single character, it
starts producing garbage. It doesn't matter if you type the characters
isolated (so that the FIFO is empty all the time) or if you send a
string via the clipboard, so that the characters get "clocked out"
back to back (and buffered in the UART's 16byte FIFO in the process).

The waveform is fairly clear, either the bit is there nice and clear,
or it's completely absent - there are no glitches or weird
malformations. There's no doubt that the garbage is coming out of the
UART's "trasmitter shift register". Observed with an oscilloscope
straight at the UART's TTL level output, before RS232/485 drivers,
with nothing attached to the RS232/485 ports (no load on the drivers).
Observed on port 1 and 3 of the quad-UART chip. Unfortunately I don't
have an LPC bus analyzer to check if perhaps the data is coming
garbled from the ICH. Makes me wonder how come that everything else
works just fine, all the addresses and data on the LPC bus - just that
bit #8 gets garbled. Otherwise it might be attributed to interference
from WiFi or BlueTooth (both in the box).

Another problem is that the symptom tends to go away if you start
looking too hard or poking around. On some machines it seems to appear
after a cold boot, after a period of inactivity. On other machines, it
starts after some flawless production runtime. It definitely seems to
go away if you switch the baud rate away from 9600 and back to 9600.
And it doesn't come back after the next reboot...

An interesting aspect is, that it only occurs on Windows XP Embedded.
If the problem occurs, and I reboot to Linux (via Etherboot), I cannot
reproduce it with Minicom or other serial TTY software that I have. If
I reboot back to XPe on a CF card, you bet it's there. This is a known-
clean system with only the basic drivers: a stock Windows serial.sys,
and the next closest driver to RS232 is a Penmount touchscreen driver
(never a problem with that one, sitting fixed on its own port). I've
tried with a pristine system, before the visualization app gets
installed (the production app that works with the COM ports), and I
cannot imagine a filter driver sitting on the COM ports - in the first
place I haven't installed any, in the second place I don't know what
purpose it might have.

I'd really love to know where the gremlins are hiding this time

If you've read this far, thanks a lot for your attention.

Frank Rysanek

 

[Franc Zabkar]

On Mon, 21 Dec 2009 07:53:53 -0800 (PST), "Frantisek.Rysanek@post.cz"
<Frantisek.Rysanek@post.cz> put finger to keyboard and composed:

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.
In HyperTerminal, it looks like a string of good characters mixed with
non-ascii garbage. An interesting feature seems to be, that it does
this with *any* character you can type on the keyboard - any letters
or numbers. If you type different characters in a sequence, the
garbage doesn't occur. If you keep sending a single character, it
starts producing garbage. It doesn't matter if you type the characters
isolated (so that the FIFO is empty all the time) or if you send a
string via the clipboard, so that the characters get "clocked out"
back to back (and buffered in the UART's 16byte FIFO in the process).

What happens if you send a string of genuine 8-bit characters, eg
extended ASCII? This will force Windows to "think about" the 8th bit,
whereas anything you type at the keyboard will usually be 7 bits.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

 

[whit3rd]

On Dec 21, 7:53 am, "Frantisek.Rysa...@post.cz"
<Frantisek.Rysa...@post.cz> wrote:

Strange as it may seem to the majority PC user nowadays, in our
industrial process control practice we're still using RS232 and its
flavours RS485, RS422. The problem at hand occurs in a [brand
censored] panel PC
.... using a [brand censored] quad UART chip, that connects to
the ICH via an LPC bus. The quad UART chip has some configurable
"industrial" features, such as TEMT bit exported to an outer modem
control signal (for HW-based RS485 RX/TX steering) and something
called "9bit mode".

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.

The waveform is fairly clear, either the bit is there nice and clear,
or it's completely absent - there are no glitches or weird
malformations. There's no doubt that the garbage is coming out of the
UART's "trasmitter shift register". Observed with an oscilloscope
straight at the UART's TTL level output, before RS232/485 drivers,
with nothing attached to the RS232/485 ports (no load on the drivers).
Observed on port 1 and 3 of the quad-UART chip.

I'd really love to know where the gremlins are hiding this time

Well, there's two hints: first, it doesn't happen in Linux. Second,
it
'comes and goes'.

Alas, that leaves two possibilities: a bit of background software that
reinitializes the UART registers and is unaware of the FOUR ports
that are there, which inadvertently changes your '8n1' settings
but which changes it back to the correct value later. It would
be rational to suspect other serial processes (IRDA as well
as COM ports). You've already looked there, though.

And, perhaps there's a bad bypass capacitor near the UART, and
it allows the power to warble enough to change a logic
threshold. That would be heat-related, you might be able to
use a hot-air gun and create the symptom.

 

[tlvp]

On Mon, 21 Dec 2009 10:53:53 -0500, Frantisek.Rysanek@post.cz <Frantisek.Rysanek@post.cz> wrote:

Dear Everyone,

apologies for cross-posting, I'm wondering if some of the veterans of
10-15 years ago are still reading these USENET groups...
I'm sending this problem description just in case the weird symptoms
ring a bell with someone - if someone happens to have a past
experience that might resemble my symptoms.
I will deliberately not name the vendors involved - we are not sure
exactly where the problem is.

Strange as it may seem to the majority PC user nowadays, in our
industrial process control practice we're still using RS232 and its
flavours RS485, RS422. The problem at hand occurs in a [brand
censored] panel PC (that's an LCD with an embedded motherboard in a
flat wallmount box), that's based on an Intel Atom, coupled with the
i945GSE chipset (including some ICH7 flavour for a south bridge). The
PC doesn't seem to contain a full-fledged SuperIO chip (no floppy, no
PS2, no LPT/joystick, just USB) and its three serial ports are
implemented using a [brand censored] quad UART chip, that connects to
the ICH via an LPC bus. The quad UART chip has some configurable
"industrial" features, such as TEMT bit exported to an outer modem
control signal (for HW-based RS485 RX/TX steering) and something
called "9bit mode".

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.
In HyperTerminal, it looks like a string of good characters mixed with
non-ascii garbage. An interesting feature seems to be, that it does
this with *any* character you can type on the keyboard - any letters
or numbers. If you type different characters in a sequence, the
garbage doesn't occur. If you keep sending a single character, it
starts producing garbage. It doesn't matter if you type the characters
isolated (so that the FIFO is empty all the time) or if you send a
string via the clipboard, so that the characters get "clocked out"
back to back (and buffered in the UART's 16byte FIFO in the process).

The waveform is fairly clear, either the bit is there nice and clear,
or it's completely absent - there are no glitches or weird
malformations. There's no doubt that the garbage is coming out of the
UART's "trasmitter shift register". Observed with an oscilloscope
straight at the UART's TTL level output, before RS232/485 drivers,
with nothing attached to the RS232/485 ports (no load on the drivers).
Observed on port 1 and 3 of the quad-UART chip. Unfortunately I don't
have an LPC bus analyzer to check if perhaps the data is coming
garbled from the ICH. Makes me wonder how come that everything else
works just fine, all the addresses and data on the LPC bus - just that
bit #8 gets garbled. Otherwise it might be attributed to interference
from WiFi or BlueTooth (both in the box).

Another problem is that the symptom tends to go away if you start
looking too hard or poking around. On some machines it seems to appear
after a cold boot, after a period of inactivity. On other machines, it
starts after some flawless production runtime. It definitely seems to
go away if you switch the baud rate away from 9600 and back to 9600.
And it doesn't come back after the next reboot...

An interesting aspect is, that it only occurs on Windows XP Embedded.
If the problem occurs, and I reboot to Linux (via Etherboot), I cannot
reproduce it with Minicom or other serial TTY software that I have. If
I reboot back to XPe on a CF card, you bet it's there. This is a known-
clean system with only the basic drivers: a stock Windows serial.sys,
and the next closest driver to RS232 is a Penmount touchscreen driver
(never a problem with that one, sitting fixed on its own port). I've
tried with a pristine system, before the visualization app gets
installed (the production app that works with the COM ports), and I
cannot imagine a filter driver sitting on the COM ports - in the first
place I haven't installed any, in the second place I don't know what
purpose it might have.

I'd really love to know where the gremlins are hiding this time

If you've read this far, thanks a lot for your attention.

Frank Rysanek

You speak of opening "the HyperTerminal" -- is that the terminal app
that's part of Win XP? If so, be aware that it itself is flawed, at
least in my experience: when I was using it to capture data from an
RS-232 serial line communications link, it would habitually and
consistently buffer its capture contents so badly that scrolling
back to earlier parts of the capture, that *had* looked OK at first,
showed very badly garbled contents.

My solution was to replace it with some other Terminal app, coming
from the public domain, that turned out *not* to manifest such issues.

No guarantee that that's where *your* issues arise, of course, but as
the issue arises under XP and not under Linux, it's a thought ... .

HTH; and cheers, -- tlvp



--
Avant de repondre, jeter la poubelle, SVP

 

On Dec 21, 7:53 am, "Frantisek.Rysa...@post.cz"
<Frantisek.Rysa...@post.cz> wrote:

Dear Everyone,

apologies for cross-posting, I'm wondering if some of the veterans of
10-15 years ago are still reading these USENET groups...
I'm sending this problem description just in case the weird symptoms
ring a bell with someone - if someone happens to have a past
experience that might resemble my symptoms.
I will deliberately not name the vendors involved - we are not sure
exactly where the problem is.

Strange as it may seem to the majority PC user nowadays, in our
industrial process control practice we're still using RS232 and its
flavours RS485, RS422. The problem at hand occurs in a [brand
censored] panel PC (that's an LCD with an embedded motherboard in a
flat wallmount box), that's based on an Intel Atom, coupled with the
i945GSE chipset (including some ICH7 flavour for a south bridge). The
PC doesn't seem to contain a full-fledged SuperIO chip (no floppy, no
PS2, no LPT/joystick, just USB) and its three serial ports are
implemented using a [brand censored] quad UART chip, that connects to
the ICH via an LPC bus. The quad UART chip has some configurable
"industrial" features, such as TEMT bit exported to an outer modem
control signal (for HW-based RS485 RX/TX steering) and something
called "9bit mode".

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.
In HyperTerminal, it looks like a string of good characters mixed with
non-ascii garbage. An interesting feature seems to be, that it does
this with *any* character you can type on the keyboard - any letters
or numbers. If you type different characters in a sequence, the
garbage doesn't occur. If you keep sending a single character, it
starts producing garbage. It doesn't matter if you type the characters
isolated (so that the FIFO is empty all the time) or if you send a
string via the clipboard, so that the characters get "clocked out"
back to back (and buffered in the UART's 16byte FIFO in the process).

The waveform is fairly clear, either the bit is there nice and clear,
or it's completely absent - there are no glitches or weird
malformations. There's no doubt that the garbage is coming out of the
UART's "trasmitter shift register". Observed with an oscilloscope
straight at the UART's TTL level output, before RS232/485 drivers,
with nothing attached to the RS232/485 ports (no load on the drivers).
Observed on port 1 and 3 of the quad-UART chip. Unfortunately I don't
have an LPC bus analyzer to check if perhaps the data is coming
garbled from the ICH. Makes me wonder how come that everything else
works just fine, all the addresses and data on the LPC bus - just that
bit #8 gets garbled. Otherwise it might be attributed to interference
from WiFi or BlueTooth (both in the box).

Another problem is that the symptom tends to go away if you start
looking too hard or poking around. On some machines it seems to appear
after a cold boot, after a period of inactivity. On other machines, it
starts after some flawless production runtime. It definitely seems to
go away if you switch the baud rate away from 9600 and back to 9600.
And it doesn't come back after the next reboot...

An interesting aspect is, that it only occurs on Windows XP Embedded.
If the problem occurs, and I reboot to Linux (via Etherboot), I cannot
reproduce it with Minicom or other serial TTY software that I have. If
I reboot back to XPe on a CF card, you bet it's there. This is a known-
clean system with only the basic drivers: a stock Windows serial.sys,
and the next closest driver to RS232 is a Penmount touchscreen driver
(never a problem with that one, sitting fixed on its own port). I've
tried with a pristine system, before the visualization app gets
installed (the production app that works with the COM ports), and I
cannot imagine a filter driver sitting on the COM ports - in the first
place I haven't installed any, in the second place I don't know what
purpose it might have.

I'd really love to know where the gremlins are hiding this time

If you've read this far, thanks a lot for your attention.

Frank Rysanek

Is is possible the send or receive is set to 7 bits + parity and the
other set to 8 bits? that would mess up the 8th bit on 50% of the
possible characters.

G˛

 

[Nico Kadel-Garcia]

On Dec 21, 10:53 am, "Frantisek.Rysa...@post.cz"
<Frantisek.Rysa...@post.cz> wrote:

Dear Everyone,

apologies for cross-posting, I'm wondering if some of the veterans of
10-15 years ago are still reading these USENET groups...
I'm sending this problem description just in case the weird symptoms
ring a bell with someone - if someone happens to have a past
experience that might resemble my symptoms.
I will deliberately not name the vendors involved - we are not sure
exactly where the problem is.

Strange as it may seem to the majority PC user nowadays, in our
industrial process control practice we're still using RS232 and its
flavours RS485, RS422. The problem at hand occurs in a [brand
censored] panel PC (that's an LCD with an embedded motherboard in a
flat wallmount box), that's based on an Intel Atom, coupled with the
i945GSE chipset (including some ICH7 flavour for a south bridge). The
PC doesn't seem to contain a full-fledged SuperIO chip (no floppy, no
PS2, no LPT/joystick, just USB) and its three serial ports are
implemented using a [brand censored] quad UART chip, that connects to
the ICH via an LPC bus. The quad UART chip has some configurable
"industrial" features, such as TEMT bit exported to an outer modem
control signal (for HW-based RS485 RX/TX steering) and something
called "9bit mode".

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.
In HyperTerminal, it looks like a string of good characters mixed with
non-ascii garbage. An interesting feature seems to be, that it does
this with *any* character you can type on the keyboard - any letters
or numbers. If you type different characters in a sequence, the
garbage doesn't occur. If you keep sending a single character, it
starts producing garbage. It doesn't matter if you type the characters
isolated (so that the FIFO is empty all the time) or if you send a
string via the clipboard, so that the characters get "clocked out"
back to back (and buffered in the UART's 16byte FIFO in the process).

The waveform is fairly clear, either the bit is there nice and clear,
or it's completely absent - there are no glitches or weird
malformations. There's no doubt that the garbage is coming out of the
UART's "trasmitter shift register". Observed with an oscilloscope
straight at the UART's TTL level output, before RS232/485 drivers,
with nothing attached to the RS232/485 ports (no load on the drivers).
Observed on port 1 and 3 of the quad-UART chip. Unfortunately I don't
have an LPC bus analyzer to check if perhaps the data is coming
garbled from the ICH. Makes me wonder how come that everything else
works just fine, all the addresses and data on the LPC bus - just that
bit #8 gets garbled. Otherwise it might be attributed to interference
from WiFi or BlueTooth (both in the box).

Another problem is that the symptom tends to go away if you start
looking too hard or poking around. On some machines it seems to appear
after a cold boot, after a period of inactivity. On other machines, it
starts after some flawless production runtime. It definitely seems to
go away if you switch the baud rate away from 9600 and back to 9600.
And it doesn't come back after the next reboot...

An interesting aspect is, that it only occurs on Windows XP Embedded.
If the problem occurs, and I reboot to Linux (via Etherboot), I cannot
reproduce it with Minicom or other serial TTY software that I have. If
I reboot back to XPe on a CF card, you bet it's there. This is a known-
clean system with only the basic drivers: a stock Windows serial.sys,
and the next closest driver to RS232 is a Penmount touchscreen driver
(never a problem with that one, sitting fixed on its own port). I've
tried with a pristine system, before the visualization app gets
installed (the production app that works with the COM ports), and I
cannot imagine a filter driver sitting on the COM ports - in the first
place I haven't installed any, in the second place I don't know what
purpose it might have.

I'd really love to know where the gremlins are hiding this time

If you've read this far, thanks a lot for your attention.

Frank Rysanek

You have a "stock Windows serial system"? No Windows updates, no
driver updates?

I'd suspect a problem right there. Go ahead and try *ALL* the updates.
And since serial support is not Windows strong point, and especially
since Hyperterminal is an incredibly limited, try installing and using
the 'Putty' freeware, which has decent serial support and vastly
better terminal emulation.

Given the concatenation of somewhat oddball chipsets in this system,
and the claim that it works properly under Linux, I'd suspect driver
issues, particularly flow control handling. Are your serial devices
actually wired correctly for hardware flow control? Many well-meaning
but clueless engineers get the RS-232 signals for different devices
miswired, and never notice because they've mishandled flow control and
don't use it much.

You should also definitely state which Windows and Linux operating
systems you're using.

 

[Andy]

On Dec 21, 8:53 am, "Frantisek.Rysa...@post.cz"
<Frantisek.Rysa...@post.cz> wrote:

Dear Everyone,

apologies for cross-posting, I'm wondering if some of the veterans of
10-15 years ago are still reading these USENET groups...
I'm sending this problem description just in case the weird symptoms
ring a bell with someone - if someone happens to have a past
experience that might resemble my symptoms.
I will deliberately not name the vendors involved - we are not sure
exactly where the problem is.

Strange as it may seem to the majority PC user nowadays, in our
industrial process control practice we're still using RS232 and its
flavours RS485, RS422. The problem at hand occurs in a [brand
censored] panel PC (that's an LCD with an embedded motherboard in a
flat wallmount box), that's based on an Intel Atom, coupled with the
i945GSE chipset (including some ICH7 flavour for a south bridge). The
PC doesn't seem to contain a full-fledged SuperIO chip (no floppy, no
PS2, no LPT/joystick, just USB) and its three serial ports are
implemented using a [brand censored] quad UART chip, that connects to
the ICH via an LPC bus. The quad UART chip has some configurable
"industrial" features, such as TEMT bit exported to an outer modem
control signal (for HW-based RS485 RX/TX steering) and something
called "9bit mode".

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.
In HyperTerminal, it looks like a string of good characters mixed with
non-ascii garbage. An interesting feature seems to be, that it does
this with *any* character you can type on the keyboard - any letters
or numbers. If you type different characters in a sequence, the
garbage doesn't occur. If you keep sending a single character, it
starts producing garbage. It doesn't matter if you type the characters
isolated (so that the FIFO is empty all the time) or if you send a
string via the clipboard, so that the characters get "clocked out"
back to back (and buffered in the UART's 16byte FIFO in the process).

The waveform is fairly clear, either the bit is there nice and clear,
or it's completely absent - there are no glitches or weird
malformations. There's no doubt that the garbage is coming out of the
UART's "trasmitter shift register". Observed with an oscilloscope
straight at the UART's TTL level output, before RS232/485 drivers,
with nothing attached to the RS232/485 ports (no load on the drivers).
Observed on port 1 and 3 of the quad-UART chip. Unfortunately I don't
have an LPC bus analyzer to check if perhaps the data is coming
garbled from the ICH. Makes me wonder how come that everything else
works just fine, all the addresses and data on the LPC bus - just that
bit #8 gets garbled. Otherwise it might be attributed to interference
from WiFi or BlueTooth (both in the box).

Another problem is that the symptom tends to go away if you start
looking too hard or poking around. On some machines it seems to appear
after a cold boot, after a period of inactivity. On other machines, it
starts after some flawless production runtime. It definitely seems to
go away if you switch the baud rate away from 9600 and back to 9600.
And it doesn't come back after the next reboot...

An interesting aspect is, that it only occurs on Windows XP Embedded.
If the problem occurs, and I reboot to Linux (via Etherboot), I cannot
reproduce it with Minicom or other serial TTY software that I have. If
I reboot back to XPe on a CF card, you bet it's there. This is a known-
clean system with only the basic drivers: a stock Windows serial.sys,
and the next closest driver to RS232 is a Penmount touchscreen driver
(never a problem with that one, sitting fixed on its own port). I've
tried with a pristine system, before the visualization app gets
installed (the production app that works with the COM ports), and I
cannot imagine a filter driver sitting on the COM ports - in the first
place I haven't installed any, in the second place I don't know what
purpose it might have.

I'd really love to know where the gremlins are hiding this time

If you've read this far, thanks a lot for your attention.

Frank Rysanek

In hyperterminal there is an option to treat incoming messages as 7
bit ascii. It sounds like you are getting 7 bits. Have you tried
this?

 

[Ian Malcolm]

"Frantisek.Rysanek@post.cz" <Frantisek.Rysanek@post.cz> wrote in
news:ddd60236-57e7-4908-bf70-91e9581fca5f@c3g2000yqd.googlegroups.com:

Dear Everyone,

apologies for cross-posting, I'm wondering if some of the veterans of
10-15 years ago are still reading these USENET groups...
I'm sending this problem description just in case the weird symptoms
ring a bell with someone - if someone happens to have a past
experience that might resemble my symptoms.
I will deliberately not name the vendors involved - we are not sure
exactly where the problem is.

Strange as it may seem to the majority PC user nowadays, in our
industrial process control practice we're still using RS232 and its
flavours RS485, RS422. The problem at hand occurs in a [brand
censored] panel PC (that's an LCD with an embedded motherboard in a
flat wallmount box), that's based on an Intel Atom, coupled with the
i945GSE chipset (including some ICH7 flavour for a south bridge). The
PC doesn't seem to contain a full-fledged SuperIO chip (no floppy, no
PS2, no LPT/joystick, just USB) and its three serial ports are
implemented using a [brand censored] quad UART chip, that connects to
the ICH via an LPC bus. The quad UART chip has some configurable
"industrial" features, such as TEMT bit exported to an outer modem
control signal (for HW-based RS485 RX/TX steering) and something
called "9bit mode".

Under some circumstances, for an unknown reason, the quad UART tends
to produce garbled TX data. You open the HyperTerminal, select a COM
port, configure it for 9600 8N1, without flow control. If you send a
string of e.g. the ASCII character "a", the 8th bit in every *second*
character is inverted. Bit 8 in the RS232 character = the last before
the stop bit = the MSB. One character okay, another character garbled.
In HyperTerminal, it looks like a string of good characters mixed with
non-ascii garbage. An interesting feature seems to be, that it does
this with *any* character you can type on the keyboard - any letters
or numbers. If you type different characters in a sequence, the
garbage doesn't occur. If you keep sending a single character, it
starts producing garbage. It doesn't matter if you type the characters
isolated (so that the FIFO is empty all the time) or if you send a
string via the clipboard, so that the characters get "clocked out"
back to back (and buffered in the UART's 16byte FIFO in the process).

The waveform is fairly clear, either the bit is there nice and clear,
or it's completely absent - there are no glitches or weird
malformations. There's no doubt that the garbage is coming out of the
UART's "trasmitter shift register". Observed with an oscilloscope
straight at the UART's TTL level output, before RS232/485 drivers,
with nothing attached to the RS232/485 ports (no load on the drivers).
Observed on port 1 and 3 of the quad-UART chip. Unfortunately I don't
have an LPC bus analyzer to check if perhaps the data is coming
garbled from the ICH. Makes me wonder how come that everything else
works just fine, all the addresses and data on the LPC bus - just that
bit #8 gets garbled. Otherwise it might be attributed to interference
from WiFi or BlueTooth (both in the box).

Another problem is that the symptom tends to go away if you start
looking too hard or poking around. On some machines it seems to appear
after a cold boot, after a period of inactivity. On other machines, it
starts after some flawless production runtime. It definitely seems to
go away if you switch the baud rate away from 9600 and back to 9600.
And it doesn't come back after the next reboot...

An interesting aspect is, that it only occurs on Windows XP Embedded.
If the problem occurs, and I reboot to Linux (via Etherboot), I cannot
reproduce it with Minicom or other serial TTY software that I have. If
I reboot back to XPe on a CF card, you bet it's there. This is a known-
clean system with only the basic drivers: a stock Windows serial.sys,
and the next closest driver to RS232 is a Penmount touchscreen driver
(never a problem with that one, sitting fixed on its own port). I've
tried with a pristine system, before the visualization app gets
installed (the production app that works with the COM ports), and I
cannot imagine a filter driver sitting on the COM ports - in the first
place I haven't installed any, in the second place I don't know what
purpose it might have.

I'd really love to know where the gremlins are hiding this time

If you've read this far, thanks a lot for your attention.

Frank Rysanek

Hyperterminal is known to garble *RECEIVED* characters under certain
circumstances if the first three characters recived are identical. This
fault, once triggered, persists until the application is exited. I wonder
if it is possible for the same bug to also affect transmit?

Please try a 3rd party terminal and see if the problem goes away...

Also censoring the uart chip brand and number will not lead you to any
answers...

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL

 

[Michael Kennedy]

Hyperterminal is known to garble *RECEIVED* characters under certain
circumstances if the first three characters recived are identical. This
fault, once triggered, persists until the application is exited. I wonder
if it is possible for the same bug to also affect transmit?

Please try a 3rd party terminal and see if the problem goes away...

Also censoring the uart chip brand and number will not lead you to any
answers...

My thoughts exactly.. Its kinda like saying I've got a broken monitor
and I want to know whats wrong with it.. It doesn't power on...

Well my first question is what make and model is it.. Often certain hardware
suffers the same problmes.

- Mike

 

[Bob Larter]

On 22/12/2009 2:53 AM, Frantisek.Rysanek@post.cz wrote:

I'd really love to know where the gremlins are hiding this time

It sounds to me like the problem is an interaction between the standard
serial driver & the extra features of the UART. Try contacting the
manufacturer of the UART, & see if they know about this 'bug' & have a
workaround, or an updated serial driver. What UART is it?

--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

 

[Frantisek.Rysanek@post.cz]

Dear gentlemen,

many thanks to all of you who responded

I'm delighted to see that the USENET is still alive, and that it's
sometimes the same
people responding to me, who used to respond ~10 years ago...

On 22 pro 2009, 15:23, Ian Malcolm wrote:

Hyperterminal is known to garble *RECEIVED* characters under certain
circumstances if the first three characters recived are identical.  This
fault, once triggered, persists until the application is exited. I wonder
if it is possible for the same bug to also affect transmit?  

And, maybe special thanks to Ian Malcolm - his bug description is the

closest to mine
If I exit Hyperterminal and start it again, the problem is typically
still there.
It survives even a power-cycle :-/

Please try a 3rd party terminal and see if the problem goes away...
[suggested by several polite people]

Yes, this is definitely something I should do.
I've seen one more occurrence of the problem,
but didn't have a chance to test this - I probably inadvertently
reset the UART and the problem went away before I tried a different
terminal.
I have Putty and CRT on my USB flash drive just in case.

Also censoring the uart chip brand and number will not lead you to any
answers...  

I know :-(

It's a matter of not biting the hand that feeds you.
After some early rookie experience in that way, I prefer to be
cautious.
After all, I'm not sure exactly where the problem is, and this
decription
could cast a shade on innocent hardware, which otherwise looks pretty
good...

What happens if you send a string of genuine 8-bit characters, eg
extended ASCII? This will force Windows to "think about" the 8th bit,
whereas anything you type at the keyboard will usually be 7 bits.

right, tried that - made a file containing a megabyte of some

character with the MSb=log.1,
and the problem was still there. Back to 7bit characters, and still it
was there.

It would be rational to suspect other serial processes
(IRDA as well as COM ports).

Ha, I haven't checked for IRDA. Makes me wonder if the IRDA modes

possibly
could use this kind of hardware feature. The UART's can work in some
IRDA modes,
but the hardware doesn't have a physical IR port, and as far as I
know, the IR modes
are not even offered in the BIOS setup for the COM ports. I can only
hope they're
properly disabled. Anyway I believe that Windows don't detect an IR
port.
Have to check to make sure - thanks for that note.
Still it makes me wonder. If the UART device was seized by some IRDA
service,
the production app running on the PC would fail to open it as a COM
port.
Sounds weird...
I was wondering if some Windows-internal ISA PnP stuff or generic
SuperIO
support could be messing with the SuperIO chip's config registers at
random.
Those are a special bank of registers with multiplexed access,
separate from
the classic ISA UART footprints in IO space.
Perhaps more likely the BIOS could have some bugs in that direction
(ACPI/SMI
handling and whatnot). Wish I had an LPC bus probe

Is is possible the send or receive is set to 7 bits + parity and the
other set to 8 bits? that would mess up the 8th bit on 50% of the
possible characters.

No. It works just fine most of the time.

The peers are set allright against each other.
Seen such misconfigurations before. This is different.
Most important it garbles every *other* character in a string.
Thanks for the suggestion though

You have a "stock Windows serial system"? No Windows updates, no
driver updates?
I'd suspect a problem right there. Go ahead and try *ALL* the updates.

It's a cut of XP Embedded based on XP SP3. I've checked the versions

of
serial.sys and serenum.sys - they're the same as on my laptop,
with Windows Update active.

Given the concatenation of somewhat oddball chipsets in this system,
and the claim that it works properly under Linux, I'd suspect driver
issues, particularly flow control handling. Are your serial devices
actually wired correctly for hardware flow control?

no they're not You _don't_ use flow control on RS485.

Anyway a flow control misconfiguration behaves very different.
You don't get anything transmitted (the write() syscall blocks),
or you get whole characters lost at the other end (FIFO overruns).

Many well-meaning but clueless engineers get the RS-232
signals for different devices miswired, and never notice because
they've mishandled flow control and don't use it much.

[chuckle] don't tell me about well-meaning engineers

What the Taiwanese HW designers can come up with...
Such as auto-loopback relays on Ethernet ports, in hardware
intended for firewall applications... or they use Linux in an embedded
box,
are soo very secretive about it (except that you can see the version
strings
in the firmware images available for download), and they can't seem to
get *default routing* right, and they have bugs in serial port
handling
on a great 16C950 UART (those are two areas where Linux has been
okay for decades now, in my experience).

You should also definitely state which Windows and Linux operating
systems you're using.

the production OS is XPe, derived from XP SP3 (Czech locale I

believe).

The Linux that I'm using for tests, is an in-house mini-distro
assembled by hand
(scripted file copy) based on Fedora 5, with a 2.6.28.6 kernel
(custom config). Booting via PXE and working just fine with my
tools

----

The lasting problem is that I keep getting pieces of the suspected
hardware
RMA'ed due to irrelevant problems (software misconfigurations, RS485
wiring sins),
and only now and then an odd piece happens to show the "flipping bit"
symptom.
Based on the set of observations so far, I can't even tell if the
"flipping bit syndrome in Hyperterminal" was to blame for a particular
production
malfunction, or if it was just the other problem I found on site
This is something I have to sort through myselfs.

The publishable results of this ongoing customer case so far have
been:

1) a snippet of Mingw C++ code that attempts to mimick the
"hyperterminal reset"
(I straced hyperterminal to see what it does at the level of
syscalls,
and then I tried to reproduce that at the level of DLL function
calls
http://www.fccps.cz/download/adv/frr/COMRESET.zip
I've hooked it up into the startup sequence of the last culprit
just in case.

2) a brain-dump of collected thoughts on RS485 grounding and
termination.
My head tends to relax if I write things down an publish for the
benefit of others
(provided that they can read through the mess
http://www.fccps.cz/download/adv/frr/RS485/RS485.html

The important point is that I'm still having fun

Thanks for your help everybody, take care

Frank Rysanek

 

[Sansui Samari]

On Jan 26, 9:04 am, "Frantisek.Rysa...@post.cz"
<Frantisek.Rysa...@post.cz> wrote:

Dear gentlemen,

many thanks to all of you who responded

I'm delighted to see that the USENET is still alive, and that it's
sometimes the same
people responding to me, who used to respond ~10 years ago...

On 22 pro 2009, 15:23, Ian Malcolm wrote:

Hyperterminal is known to garble *RECEIVED* characters under certain
circumstances if the first three characters recived are identical.  This
fault, once triggered, persists until the application is exited. I wonder
if it is possible for the same bug to also affect transmit?  

And, maybe special thanks to Ian Malcolm - his bug description is the
closest to mine
If I exit Hyperterminal and start it again, the problem is typically
still there.
It survives even a power-cycle :-/

Please try a 3rd party terminal and see if the problem goes away...

[suggested by several polite people]

Yes, this is definitely something I should do.
I've seen one more occurrence of the problem,
but didn't have a chance to test this - I probably inadvertently
reset the UART and the problem went away before I tried a different
terminal.
I have Putty and CRT on my USB flash drive just in case.

Also censoring the uart chip brand and number will not lead you to any
answers...  

I know :-(
It's a matter of not biting the hand that feeds you.
After some early rookie experience in that way, I prefer to be
cautious.
After all, I'm not sure exactly where the problem is, and this
decription
could cast a shade on innocent hardware, which otherwise looks pretty
good...

What happens if you send a string of genuine 8-bit characters, eg
extended ASCII? This will force Windows to "think about" the 8th bit,
whereas anything you type at the keyboard will usually be 7 bits.

right, tried that - made a file containing a megabyte of some
character with the MSb=log.1,
and the problem was still there. Back to 7bit characters, and still it
was there.

It would be rational to suspect other serial processes
(IRDA as well as COM ports).

Ha, I haven't checked for IRDA. Makes me wonder if the IRDA modes
possibly
could use this kind of hardware feature. The UART's can work in some
IRDA modes,
but the hardware doesn't have a physical IR port, and as far as I
know, the IR modes
are not even offered in the BIOS setup for the COM ports. I can only
hope they're
properly disabled. Anyway I believe that Windows don't detect an IR
port.
Have to check to make sure - thanks for that note.
Still it makes me wonder. If the UART device was seized by some IRDA
service,
the production app running on the PC would fail to open it as a COM
port.
Sounds weird...
I was wondering if some Windows-internal ISA PnP stuff or generic
SuperIO
support could be messing with the SuperIO chip's config registers at
random.
Those are a special bank of registers with multiplexed access,
separate from
the classic ISA UART footprints in IO space.
Perhaps more likely the BIOS could have some bugs in that direction
(ACPI/SMI
handling and whatnot). Wish I had an LPC bus probe

Is is possible the send or receive is set to 7 bits + parity and the
other set to 8 bits? that would mess up the 8th bit on 50% of the
possible characters.

No. It works just fine most of the time.
The peers are set allright against each other.
Seen such misconfigurations before. This is different.
Most important it garbles every *other* character in a string.
Thanks for the suggestion though

You have a "stock Windows serial system"? No Windows updates, no
driver updates?
I'd suspect a problem right there. Go ahead and try *ALL* the updates.

It's a cut of XP Embedded based on XP SP3. I've checked the versions
of
serial.sys and serenum.sys - they're the same as on my laptop,
with Windows Update active.

Given the concatenation of somewhat oddball chipsets in this system,
and the claim that it works properly under Linux, I'd suspect driver
issues, particularly flow control handling. Are your serial devices
actually wired correctly for hardware flow control?

no they're not You _don't_ use flow control on RS485.
Anyway a flow control misconfiguration behaves very different.
You don't get anything transmitted (the write() syscall blocks),
or you get whole characters lost at the other end (FIFO overruns).

Many well-meaning but clueless engineers get the RS-232
signals for different devices miswired, and never notice because
they've mishandled flow control and don't use it much.

[chuckle] don't tell me about well-meaning engineers
What the Taiwanese HW designers can come up with...
Such as auto-loopback relays on Ethernet ports, in hardware
intended for firewall applications... or they use Linux in an embedded
box,
are soo very secretive about it (except that you can see the version
strings
in the firmware images available for download), and they can't seem to
get *default routing* right, and they have bugs in serial port
handling
on a great 16C950 UART (those are two areas where Linux has been
okay for decades now, in my experience).

You should also definitely state which Windows and Linux operating
systems you're using.

the production OS is XPe, derived from XP SP3 (Czech locale I
believe).

The Linux that I'm using for tests, is an in-house mini-distro
assembled by hand
(scripted file copy) based on Fedora 5, with a 2.6.28.6 kernel
(custom config). Booting via PXE and working just fine with my
tools

----

The lasting problem is that I keep getting pieces of the suspected
hardware
RMA'ed due to irrelevant problems (software misconfigurations, RS485
wiring sins),
and only now and then an odd piece happens to show the "flipping bit"
symptom.
Based on the set of  observations so far, I can't even tell if the
"flipping bit syndrome in Hyperterminal" was to blame for a particular
production
malfunction, or if it was just the other problem I found on site
This is something I have to sort through myselfs.

The publishable results of this ongoing customer case so far have
been:

1) a snippet of Mingw C++ code that attempts to mimick the
"hyperterminal reset"
    (I straced hyperterminal to see what it does at the level of
syscalls,
     and then I tried to reproduce that at the level of DLL function
calls
   http://www.fccps.cz/download/adv/frr/COMRESET.zip
    I've hooked it up into the startup sequence of the last culprit
just in case.

2) a brain-dump of collected thoughts on RS485 grounding and
termination.
    My head tends to relax if I write things down an publish for the
benefit of others
    (provided that they can read through the mess
   http://www.fccps.cz/download/adv/frr/RS485/RS485.html

The important point is that I'm still having fun

Thanks for your help everybody, take care

Frank Rysanek

I had similar issues when I was writing a user interface for a machine
that had a windows pc interfacing with a PLC. We were using win98 if
I remember correctly. I think the uart and windows had an issue
because of the way windows would multitask. Windows would lock the
application just long enough to put it out of sync with the uart, and
cause garbled data, or a frozen application. I think there were also
problems with keeping other applications from accessing the port, even
though it should have been locked. At first, I would have to restart
windows when the app crashed. But then I rewrote the app, so I could
just re-initiate communications when it failed. I have a binder
around here somewhere, with our notes and data sheets and the like. I
don't know if they'll apply to you, but I'll post a better explanation
if I can find them.

I must be getting old when I remember fixing something, but don't
remember how the hell I did it. Then tell a long drawn out story with
no useful information whatsoever.



-Lazers

 

[Sansui Samari]

On Jan 26, 9:04 am, "Frantisek.Rysa...@post.cz"
<Frantisek.Rysa...@post.cz> wrote:

Dear gentlemen,

many thanks to all of you who responded

I'm delighted to see that the USENET is still alive, and that it's
sometimes the same
people responding to me, who used to respond ~10 years ago...

On 22 pro 2009, 15:23, Ian Malcolm wrote:

Hyperterminal is known to garble *RECEIVED* characters under certain
circumstances if the first three characters recived are identical.  This
fault, once triggered, persists until the application is exited. I wonder
if it is possible for the same bug to also affect transmit?  

And, maybe special thanks to Ian Malcolm - his bug description is the
closest to mine
If I exit Hyperterminal and start it again, the problem is typically
still there.
It survives even a power-cycle :-/

Please try a 3rd party terminal and see if the problem goes away...

[suggested by several polite people]

Yes, this is definitely something I should do.
I've seen one more occurrence of the problem,
but didn't have a chance to test this - I probably inadvertently
reset the UART and the problem went away before I tried a different
terminal.
I have Putty and CRT on my USB flash drive just in case.

Also censoring the uart chip brand and number will not lead you to any
answers...  

I know :-(
It's a matter of not biting the hand that feeds you.
After some early rookie experience in that way, I prefer to be
cautious.
After all, I'm not sure exactly where the problem is, and this
decription
could cast a shade on innocent hardware, which otherwise looks pretty
good...

What happens if you send a string of genuine 8-bit characters, eg
extended ASCII? This will force Windows to "think about" the 8th bit,
whereas anything you type at the keyboard will usually be 7 bits.

right, tried that - made a file containing a megabyte of some
character with the MSb=log.1,
and the problem was still there. Back to 7bit characters, and still it
was there.

It would be rational to suspect other serial processes
(IRDA as well as COM ports).

Ha, I haven't checked for IRDA. Makes me wonder if the IRDA modes
possibly
could use this kind of hardware feature. The UART's can work in some
IRDA modes,
but the hardware doesn't have a physical IR port, and as far as I
know, the IR modes
are not even offered in the BIOS setup for the COM ports. I can only
hope they're
properly disabled. Anyway I believe that Windows don't detect an IR
port.
Have to check to make sure - thanks for that note.
Still it makes me wonder. If the UART device was seized by some IRDA
service,
the production app running on the PC would fail to open it as a COM
port.
Sounds weird...
I was wondering if some Windows-internal ISA PnP stuff or generic
SuperIO
support could be messing with the SuperIO chip's config registers at
random.
Those are a special bank of registers with multiplexed access,
separate from
the classic ISA UART footprints in IO space.
Perhaps more likely the BIOS could have some bugs in that direction
(ACPI/SMI
handling and whatnot). Wish I had an LPC bus probe

Is is possible the send or receive is set to 7 bits + parity and the
other set to 8 bits? that would mess up the 8th bit on 50% of the
possible characters.

No. It works just fine most of the time.
The peers are set allright against each other.
Seen such misconfigurations before. This is different.
Most important it garbles every *other* character in a string.
Thanks for the suggestion though

You have a "stock Windows serial system"? No Windows updates, no
driver updates?
I'd suspect a problem right there. Go ahead and try *ALL* the updates.

It's a cut of XP Embedded based on XP SP3. I've checked the versions
of
serial.sys and serenum.sys - they're the same as on my laptop,
with Windows Update active.

Given the concatenation of somewhat oddball chipsets in this system,
and the claim that it works properly under Linux, I'd suspect driver
issues, particularly flow control handling. Are your serial devices
actually wired correctly for hardware flow control?

no they're not You _don't_ use flow control on RS485.
Anyway a flow control misconfiguration behaves very different.
You don't get anything transmitted (the write() syscall blocks),
or you get whole characters lost at the other end (FIFO overruns).

Many well-meaning but clueless engineers get the RS-232
signals for different devices miswired, and never notice because
they've mishandled flow control and don't use it much.

[chuckle] don't tell me about well-meaning engineers
What the Taiwanese HW designers can come up with...
Such as auto-loopback relays on Ethernet ports, in hardware
intended for firewall applications... or they use Linux in an embedded
box,
are soo very secretive about it (except that you can see the version
strings
in the firmware images available for download), and they can't seem to
get *default routing* right, and they have bugs in serial port
handling
on a great 16C950 UART (those are two areas where Linux has been
okay for decades now, in my experience).

You should also definitely state which Windows and Linux operating
systems you're using.

the production OS is XPe, derived from XP SP3 (Czech locale I
believe).

The Linux that I'm using for tests, is an in-house mini-distro
assembled by hand
(scripted file copy) based on Fedora 5, with a 2.6.28.6 kernel
(custom config). Booting via PXE and working just fine with my
tools

----

The lasting problem is that I keep getting pieces of the suspected
hardware
RMA'ed due to irrelevant problems (software misconfigurations, RS485
wiring sins),
and only now and then an odd piece happens to show the "flipping bit"
symptom.
Based on the set of  observations so far, I can't even tell if the
"flipping bit syndrome in Hyperterminal" was to blame for a particular
production
malfunction, or if it was just the other problem I found on site
This is something I have to sort through myselfs.

The publishable results of this ongoing customer case so far have
been:

1) a snippet of Mingw C++ code that attempts to mimick the
"hyperterminal reset"
    (I straced hyperterminal to see what it does at the level of
syscalls,
     and then I tried to reproduce that at the level of DLL function
calls
   http://www.fccps.cz/download/adv/frr/COMRESET.zip
    I've hooked it up into the startup sequence of the last culprit
just in case.

2) a brain-dump of collected thoughts on RS485 grounding and
termination.
    My head tends to relax if I write things down an publish for the
benefit of others
    (provided that they can read through the mess
   http://www.fccps.cz/download/adv/frr/RS485/RS485.html

The important point is that I'm still having fun

Thanks for your help everybody, take care

Frank Rysanek

You might try posting here.
http://omgili.com/probleme-rs232-sp3-windows-xp

 

[Sansui Samari]

On Jan 28, 12:40 am, Sansui Samari <jimjam1...@gmail.com> wrote:

On Jan 26, 9:04 am, "Frantisek.Rysa...@post.cz"



Frantisek.Rysa...@post.cz> wrote:
Dear gentlemen,

many thanks to all of you who responded

I'm delighted to see that the USENET is still alive, and that it's
sometimes the same
people responding to me, who used to respond ~10 years ago...

On 22 pro 2009, 15:23, Ian Malcolm wrote:

Hyperterminal is known to garble *RECEIVED* characters under certain
circumstances if the first three characters recived are identical.  This
fault, once triggered, persists until the application is exited. I wonder
if it is possible for the same bug to also affect transmit?  

And, maybe special thanks to Ian Malcolm - his bug description is the
closest to mine
If I exit Hyperterminal and start it again, the problem is typically
still there.
It survives even a power-cycle :-/

Please try a 3rd party terminal and see if the problem goes away...

[suggested by several polite people]

Yes, this is definitely something I should do.
I've seen one more occurrence of the problem,
but didn't have a chance to test this - I probably inadvertently
reset the UART and the problem went away before I tried a different
terminal.
I have Putty and CRT on my USB flash drive just in case.

Also censoring the uart chip brand and number will not lead you to any
answers...  

I know :-(
It's a matter of not biting the hand that feeds you.
After some early rookie experience in that way, I prefer to be
cautious.
After all, I'm not sure exactly where the problem is, and this
decription
could cast a shade on innocent hardware, which otherwise looks pretty
good...

What happens if you send a string of genuine 8-bit characters, eg
extended ASCII? This will force Windows to "think about" the 8th bit,
whereas anything you type at the keyboard will usually be 7 bits.

right, tried that - made a file containing a megabyte of some
character with the MSb=log.1,
and the problem was still there. Back to 7bit characters, and still it
was there.

It would be rational to suspect other serial processes
(IRDA as well as COM ports).

Ha, I haven't checked for IRDA. Makes me wonder if the IRDA modes
possibly
could use this kind of hardware feature. The UART's can work in some
IRDA modes,
but the hardware doesn't have a physical IR port, and as far as I
know, the IR modes
are not even offered in the BIOS setup for the COM ports. I can only
hope they're
properly disabled. Anyway I believe that Windows don't detect an IR
port.
Have to check to make sure - thanks for that note.
Still it makes me wonder. If the UART device was seized by some IRDA
service,
the production app running on the PC would fail to open it as a COM
port.
Sounds weird...
I was wondering if some Windows-internal ISA PnP stuff or generic
SuperIO
support could be messing with the SuperIO chip's config registers at
random.
Those are a special bank of registers with multiplexed access,
separate from
the classic ISA UART footprints in IO space.
Perhaps more likely the BIOS could have some bugs in that direction
(ACPI/SMI
handling and whatnot). Wish I had an LPC bus probe

Is is possible the send or receive is set to 7 bits + parity and the
other set to 8 bits? that would mess up the 8th bit on 50% of the
possible characters.

No. It works just fine most of the time.
The peers are set allright against each other.
Seen such misconfigurations before. This is different.
Most important it garbles every *other* character in a string.
Thanks for the suggestion though

You have a "stock Windows serial system"? No Windows updates, no
driver updates?
I'd suspect a problem right there. Go ahead and try *ALL* the updates..

It's a cut of XP Embedded based on XP SP3. I've checked the versions
of
serial.sys and serenum.sys - they're the same as on my laptop,
with Windows Update active.

Given the concatenation of somewhat oddball chipsets in this system,
and the claim that it works properly under Linux, I'd suspect driver
issues, particularly flow control handling. Are your serial devices
actually wired correctly for hardware flow control?

no they're not You _don't_ use flow control on RS485.
Anyway a flow control misconfiguration behaves very different.
You don't get anything transmitted (the write() syscall blocks),
or you get whole characters lost at the other end (FIFO overruns).

Many well-meaning but clueless engineers get the RS-232
signals for different devices miswired, and never notice because
they've mishandled flow control and don't use it much.

[chuckle] don't tell me about well-meaning engineers
What the Taiwanese HW designers can come up with...
Such as auto-loopback relays on Ethernet ports, in hardware
intended for firewall applications... or they use Linux in an embedded
box,
are soo very secretive about it (except that you can see the version
strings
in the firmware images available for download), and they can't seem to
get *default routing* right, and they have bugs in serial port
handling
on a great 16C950 UART (those are two areas where Linux has been
okay for decades now, in my experience).

You should also definitely state which Windows and Linux operating
systems you're using.

the production OS is XPe, derived from XP SP3 (Czech locale I
believe).

The Linux that I'm using for tests, is an in-house mini-distro
assembled by hand
(scripted file copy) based on Fedora 5, with a 2.6.28.6 kernel
(custom config). Booting via PXE and working just fine with my
tools

----

The lasting problem is that I keep getting pieces of the suspected
hardware
RMA'ed due to irrelevant problems (software misconfigurations, RS485
wiring sins),
and only now and then an odd piece happens to show the "flipping bit"
symptom.
Based on the set of  observations so far, I can't even tell if the
"flipping bit syndrome in Hyperterminal" was to blame for a particular
production
malfunction, or if it was just the other problem I found on site
This is something I have to sort through myselfs.

The publishable results of this ongoing customer case so far have
been:

1) a snippet of Mingw C++ code that attempts to mimick the
"hyperterminal reset"
    (I straced hyperterminal to see what it does at the level of
syscalls,
     and then I tried to reproduce that at the level of DLL function
calls
   http://www.fccps.cz/download/adv/frr/COMRESET.zip
    I've hooked it up into the startup sequence of the last culprit
just in case.

2) a brain-dump of collected thoughts on RS485 grounding and
termination.
    My head tends to relax if I write things down an publish for the
benefit of others
    (provided that they can read through the mess
   http://www.fccps.cz/download/adv/frr/RS485/RS485.html

The important point is that I'm still having fun

Thanks for your help everybody, take care

Frank Rysanek

You might try posting here.http://omgili.com/probleme-rs232-sp3-windows-xp

And maybe searching through here...
http://www.arcelect.com/technica.htm

 

[G B]

Frank,

I saw a similar problem but it was running at approx 1Mb/s. I had problems
with clock skew in the devices. The clock in the send device was not the
same as the receive device. Hence the clocks would slowly drift over time.
I usually destroyed the 8th bit. Sometimes it would be just fine. I saw
the part about every other character which made me think if there is no
character pacing, it might take a full character time to resync. Just an
idea..

-Greg
p.s. I liked your ground loop discussion and graphs. Good info!

<Frantisek.Rysanek@post.cz> wrote in message
news:82454c4a-fdd6-445a-b5fe-329259af3f28@m16g2000yqc.googlegroups.com...
Dear gentlemen,

many thanks to all of you who responded

I'm delighted to see that the USENET is still alive, and that it's
sometimes the same
people responding to me, who used to respond ~10 years ago...

On 22 pro 2009, 15:23, Ian Malcolm wrote:

Hyperterminal is known to garble *RECEIVED* characters under certain
circumstances if the first three characters recived are identical. This
fault, once triggered, persists until the application is exited. I wonder
if it is possible for the same bug to also affect transmit?

And, maybe special thanks to Ian Malcolm - his bug description is the

closest to mine
If I exit Hyperterminal and start it again, the problem is typically
still there.
It survives even a power-cycle :-/

Please try a 3rd party terminal and see if the problem goes away...
[suggested by several polite people]

Yes, this is definitely something I should do.
I've seen one more occurrence of the problem,
but didn't have a chance to test this - I probably inadvertently
reset the UART and the problem went away before I tried a different
terminal.
I have Putty and CRT on my USB flash drive just in case.

Also censoring the uart chip brand and number will not lead you to any
answers...

I know :-(

It's a matter of not biting the hand that feeds you.
After some early rookie experience in that way, I prefer to be
cautious.
After all, I'm not sure exactly where the problem is, and this
decription
could cast a shade on innocent hardware, which otherwise looks pretty
good...

What happens if you send a string of genuine 8-bit characters, eg
extended ASCII? This will force Windows to "think about" the 8th bit,
whereas anything you type at the keyboard will usually be 7 bits.

right, tried that - made a file containing a megabyte of some

character with the MSb=log.1,
and the problem was still there. Back to 7bit characters, and still it
was there.

It would be rational to suspect other serial processes
(IRDA as well as COM ports).

Ha, I haven't checked for IRDA. Makes me wonder if the IRDA modes

possibly
could use this kind of hardware feature. The UART's can work in some
IRDA modes,
but the hardware doesn't have a physical IR port, and as far as I
know, the IR modes
are not even offered in the BIOS setup for the COM ports. I can only
hope they're
properly disabled. Anyway I believe that Windows don't detect an IR
port.
Have to check to make sure - thanks for that note.
Still it makes me wonder. If the UART device was seized by some IRDA
service,
the production app running on the PC would fail to open it as a COM
port.
Sounds weird...
I was wondering if some Windows-internal ISA PnP stuff or generic
SuperIO
support could be messing with the SuperIO chip's config registers at
random.
Those are a special bank of registers with multiplexed access,
separate from
the classic ISA UART footprints in IO space.
Perhaps more likely the BIOS could have some bugs in that direction
(ACPI/SMI
handling and whatnot). Wish I had an LPC bus probe

Is is possible the send or receive is set to 7 bits + parity and the
other set to 8 bits? that would mess up the 8th bit on 50% of the
possible characters.

No. It works just fine most of the time.

The peers are set allright against each other.
Seen such misconfigurations before. This is different.
Most important it garbles every *other* character in a string.
Thanks for the suggestion though

You have a "stock Windows serial system"? No Windows updates, no
driver updates?
I'd suspect a problem right there. Go ahead and try *ALL* the updates.

It's a cut of XP Embedded based on XP SP3. I've checked the versions

of
serial.sys and serenum.sys - they're the same as on my laptop,
with Windows Update active.

Given the concatenation of somewhat oddball chipsets in this system,
and the claim that it works properly under Linux, I'd suspect driver
issues, particularly flow control handling. Are your serial devices
actually wired correctly for hardware flow control?

no they're not You _don't_ use flow control on RS485.

Anyway a flow control misconfiguration behaves very different.
You don't get anything transmitted (the write() syscall blocks),
or you get whole characters lost at the other end (FIFO overruns).

Many well-meaning but clueless engineers get the RS-232
signals for different devices miswired, and never notice because
they've mishandled flow control and don't use it much.

[chuckle] don't tell me about well-meaning engineers

What the Taiwanese HW designers can come up with...
Such as auto-loopback relays on Ethernet ports, in hardware
intended for firewall applications... or they use Linux in an embedded
box,
are soo very secretive about it (except that you can see the version
strings
in the firmware images available for download), and they can't seem to
get *default routing* right, and they have bugs in serial port
handling
on a great 16C950 UART (those are two areas where Linux has been
okay for decades now, in my experience).

You should also definitely state which Windows and Linux operating
systems you're using.

the production OS is XPe, derived from XP SP3 (Czech locale I

believe).

The Linux that I'm using for tests, is an in-house mini-distro
assembled by hand
(scripted file copy) based on Fedora 5, with a 2.6.28.6 kernel
(custom config). Booting via PXE and working just fine with my
tools

----

The lasting problem is that I keep getting pieces of the suspected
hardware
RMA'ed due to irrelevant problems (software misconfigurations, RS485
wiring sins),
and only now and then an odd piece happens to show the "flipping bit"
symptom.
Based on the set of observations so far, I can't even tell if the
"flipping bit syndrome in Hyperterminal" was to blame for a particular
production
malfunction, or if it was just the other problem I found on site
This is something I have to sort through myselfs.

The publishable results of this ongoing customer case so far have
been:

1) a snippet of Mingw C++ code that attempts to mimick the
"hyperterminal reset"
(I straced hyperterminal to see what it does at the level of
syscalls,
and then I tried to reproduce that at the level of DLL function
calls
http://www.fccps.cz/download/adv/frr/COMRESET.zip
I've hooked it up into the startup sequence of the last culprit
just in case.

2) a brain-dump of collected thoughts on RS485 grounding and
termination.
My head tends to relax if I write things down an publish for the
benefit of others
(provided that they can read through the mess
http://www.fccps.cz/download/adv/frr/RS485/RS485.html

The important point is that I'm still having fun

Thanks for your help everybody, take care

Frank Rysanek