interfacing to "another" system

  • Thread starter Antonis Konstantinos
  • Start date
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Antonis Konstantinos

Guest
Hi All,

I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)

The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.

Both systems uses 5V logic.

I have already built the system and it works fine *for now*.

Do you think that there is a more appropriate way of doing this? If so
what would you recommend ?

Thanks in advance,

Regards


--
Antonis Konstantinos
 
"Antonis Konstantinos" <antonis_konstantinos@hotmail.com> wrote in message
news:424eaa6b.0405201243.461b581@posting.google.com...
Hi All,

I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)

The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.

Both systems uses 5V logic.

I have already built the system and it works fine *for now*.

Do you think that there is a more appropriate way of doing this? If so
what would you recommend ?
Click to expand...
It depends on how far apart they are.

Leon
 
"Antonis Konstantinos" <antonis_konstantinos@hotmail.com> wrote in message
news:424eaa6b.0405201243.461b581@posting.google.com...
Hi All,

I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)

The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.

Both systems uses 5V logic.

I have already built the system and it works fine *for now*.

Do you think that there is a more appropriate way of doing this? If so
what would you recommend ?

Thanks in advance,

Regards


--
Antonis Konstantinos
Click to expand...
A fiber optic link would allow you the best communication speeds, and afford
total electrical isolation between the two systems. You can get copper to
fiber converters, or make your own. Check with LComm, Black Box, etc.. (both
are .com's)
 
"Antonis Konstantinos" <antonis_konstantinos@hotmail.com> schreef in bericht
news:424eaa6b.0405201243.461b581@posting.google.com...
Hi All,

I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)

The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.

Both systems uses 5V logic.

I have already built the system and it works fine *for now*.

Do you think that there is a more appropriate way of doing this? If so
what would you recommend ?
Click to expand...
If it is a fixed setup, and never gets unplugged, such as inside
a machine, it's okay.


--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)
 
On a sunny day (20 May 2004 13:43:08 -0700) it happened
antonis_konstantinos@hotmail.com (Antonis Konstantinos) wrote in
<424eaa6b.0405201243.461b581@posting.google.com>:

Hi All,

I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)

The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.

Both systems uses 5V logic.

I have already built the system and it works fine *for now*.

Do you think that there is a more appropriate way of doing this? If so
what would you recommend ?

Thanks in advance,

Regards
You could use MAX232 ICs to make the level rs232 compatible.
Click to expand...
So then you can use the PC serial port to test...
The signal to noise would improve from it too.
JP
 
"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:c8jfe1$pl$1@news.epidc.co.kr...
antonis_konstantinos@hotmail.com (Antonis Konstantinos) wrote in
I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)
The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.
Both systems uses 5V logic.
I have already built the system and it works fine *for now*.
Do you think that there is a more appropriate way of doing this? If so
what would you recommend ?
You could use MAX232 ICs to make the level rs232 compatible.
So then you can use the PC serial port to test...
The signal to noise would improve from it too.
Click to expand...
I've seen discrete transistors used as line drivers for "RS232" lines,
like complementary emitter-followers with enough series resistance
to make them short-immune, and it may have even acted like sort of a
terminator - and series resistors and protection diodes to the xsitor
bases on the receiving end.

This may be overkill, depending on the app.

Good Luck!
Rich
 
Antonis Konstantinos wrote:
Hi All,

I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)

The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.
Click to expand...
This is where your potential problem lies. A direct logic-level
connection between 2 systems with independent power supplies will be
subject to power sequencing problems. Since both devices are most likely
CMOS, there is a very real risk of causing destructive latchup of one of
the inputs.

Some sort of buffering to ensure safe levels while either system is
powered off is required. For the data rate you're using, an open
collector driver with a pull-up to the receiving side's power supply
should be adequate.
--
Tim Hubberstey, P.Eng. . . . . . Hardware/Software Consulting Engineer
Marmot Engineering . . . . . . . VHDL, ASICs, FPGAs, embedded systems
Vancouver, BC, Canada . . . . . . . . . . . http://www.marmot-eng.com
 
It depends on how far apart they are.
Click to expand...
at most 20cm apart. connected with a flat cable. (like the ones used
to connect Hard Drives in the PC)

--
Antonis Konstantinos
 
If it is a fixed setup, and never gets unplugged, such as inside
a machine, it's okay.
Click to expand...
Well I can say it will not be unplugged as long as it works. But what
is the idea behind that? Can you explain a bit further ?

Thanks

--
Antonis Konstantinos
 
"Antonis Konstantinos" <antonis_konstantinos@hotmail.com> schreef in bericht
news:424eaa6b.0405210127.236642b5@posting.google.com...
If it is a fixed setup, and never gets unplugged, such as inside
a machine, it's okay.

Well I can say it will not be unplugged as long as it works. But what
is the idea behind that? Can you explain a bit further ?
Click to expand...
Floating stuff, static charged users, etc. Similar to parallel
printerports on PC's that sometimes get fried. Never happens
when trying to demonstrate it, but it does happen when you
don't expect it ;)

But as another poster pointed out, you also have the issue of
powerup sequence, so it is not such a good idea to connect it
directly.

--
Thanks, Frank.
(remove 'x' and 'invalid' when replying by email)
 
On a sunny day (Fri, 21 May 2004 03:14:00 GMT) it happened "Rich Grise"
<null@example.net> wrote in <Yterc.7261$dq4.623@nwrddc01.gnilink.net>:

"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message
news:c8jfe1$pl$1@news.epidc.co.kr...
antonis_konstantinos@hotmail.com (Antonis Konstantinos) wrote in
I am now building a system which will be communicating to another
system via UART at low rates (4800 bps)
The board that I am building will be powered up from an SMPS and the
other system has its own power supply. I plan to connect the uart
lines directly (without any buffer, optocoupler etc.) to my micro and
connect the ground of each system together.
Both systems uses 5V logic.
I have already built the system and it works fine *for now*.
Do you think that there is a more appropriate way of doing this? If so
what would you recommend ?
You could use MAX232 ICs to make the level rs232 compatible.
So then you can use the PC serial port to test...
The signal to noise would improve from it too.

I've seen discrete transistors used as line drivers for "RS232" lines,
like complementary emitter-followers with enough series resistance
to make them short-immune, and it may have even acted like sort of a
terminator - and series resistors and protection diodes to the xsitor
bases on the receiving end.

This may be overkill, depending on the app.

Good Luck!
Rich
Yes this is possible, the MAX232 makes nice plus and minus voltages for
Click to expand...
you from +5V however.
Only needs a couple of electrolytics.
JP
 
In article <c8l5ee$g0$1@news.epidc.co.kr>,
Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:
[...]
Yes this is possible, the MAX232 makes nice plus and minus voltages for
you from +5V however.
Only needs a couple of electrolytics.
Click to expand...
LT1181 uses ceramics.

--
--
kensmith@rahul.net forging knowledge
 
On a sunny day (Fri, 21 May 2004 18:22:23 +0000 (UTC)) it happened
kensmith@violet.rahul.net (Ken Smith) wrote in <c8lhcv$349$1@blue.rahul.net>:

In article <c8l5ee$g0$1@news.epidc.co.kr>,
Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:
[...]
Yes this is possible, the MAX232 makes nice plus and minus voltages for
you from +5V however.
Only needs a couple of electrolytics.

LT1181 uses ceramics.
Those are cheaper?
Click to expand...
 
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