Cheap RS-232 receiver driver

[Aubrey McIntosh]

I have just finished porting the PIC 16F877 programmer that I wrote in
the summer of 2000 for a grad school course to be the host side
software of a third party programmer board's prototype (
http://www.embedinc.com/EasyProg )

There is tremendous interest in cheap, simple, reliable, idiot proof,
programmers in the PIC arena. Many of them do some kind of trick with
RS-232 signal levels, and work with some systems, not others, without
regard to standards. Hobbiest seem to be willing to spend $1,000 of
time to save the purchase of a $20 item.

I think I could make a programmer design for hobbiest that only uses
the TX, RX lines, but in the standard fashion. It would use a cheap
PIC, some passives, and possibly derive power from the RS-232 line. I
picked up a sample of the 12F629 for about $1.50 at Jameco while
getting some other stuff, and will read the data sheets later to see
if it is a contender for the project.

I would like to identify a component, the RS-232 receiver driver that
has at least 1 receive and 1 transmit channel. I would like it to be
readily available in single quantity, and cost less than $3. I don't
care if it needs external capacitors or not, but I would like a
judgement call as to least total cost, including capacitors and board
space. I know about the ST232 (Max232) but I wanted to see if there
is anything cheaper.

Also, it makes a lot of sense for me to do a USB project next. So
postings that steer in that direction are also welcome.

(crossposted, consider trimming)

 

[Wouter van Ooijen (www.vo]

There is tremendous interest in cheap, simple, reliable, idiot proof,
programmers in the PIC arena.

I sell this programmer: http://www.voti.nl/wisp628 as kit ($24) or
build ($35). Full details are also available for do-it-yourself. Seems
to be exactly what you describe, except that it exists PC software
runs on Windows, Linux, Mac, etc.

readily available in single quantity, and cost less than $3. I don't
care if it needs external capacitors or not, but I would like a
judgement call as to least total cost, including capacitors and board
space. I know about the ST232 (Max232) but I wanted to see if there
is anything cheaper.

I sell MAX232 + 4 caps for $1.69. Is that sufficiently below $3?

Also, it makes a lot of sense for me to do a USB project next. So
postings that steer in that direction are also welcome.

I sell the FT232BM USB-to-serial converter chip ($7.80). NB My sale
pages has links to all datasheets.


Wouter van Ooijen

-- ------------------------------------
http://www.voti.nl
PICmicro chips, programmers, consulting

 

[Roger Hamlett]

"Aubrey McIntosh" <mcintosh@spam.vima.austin.tx.us> wrote in message
news:3796268b.0402041247.5afa51a0@posting.google.com...

I have just finished porting the PIC 16F877 programmer that I wrote in
the summer of 2000 for a grad school course to be the host side
software of a third party programmer board's prototype (
http://www.embedinc.com/EasyProg )

There is tremendous interest in cheap, simple, reliable, idiot proof,
programmers in the PIC arena. Many of them do some kind of trick with
RS-232 signal levels, and work with some systems, not others, without
regard to standards. Hobbiest seem to be willing to spend $1,000 of
time to save the purchase of a $20 item.

I think I could make a programmer design for hobbiest that only uses
the TX, RX lines, but in the standard fashion. It would use a cheap
PIC, some passives, and possibly derive power from the RS-232 line. I
picked up a sample of the 12F629 for about $1.50 at Jameco while
getting some other stuff, and will read the data sheets later to see
if it is a contender for the project.

I would like to identify a component, the RS-232 receiver driver that
has at least 1 receive and 1 transmit channel. I would like it to be
readily available in single quantity, and cost less than $3. I don't
care if it needs external capacitors or not, but I would like a
judgement call as to least total cost, including capacitors and board
space. I know about the ST232 (Max232) but I wanted to see if there
is anything cheaper.

Also, it makes a lot of sense for me to do a USB project next. So
postings that steer in that direction are also welcome.

(crossposted, consider trimming)
I use the Dallas DS275 for this type of application. 8pin chip. one RS232

receiver, and one transmitter. It generates the required voltage on the TX
side, by 'stealing' current from the RXpin. In terms of board real estate,
it has to be about the smallest possible combination, and works well. If you
only have 5v available as the high supply rail, it technically falls
slightly short of the RS232 spec (but still seems to work fine), but if the
system is battery powered, and has 6v or more available, it then meets the
drive requirements properly. Cost is about comparable with the MAX232
(remember that the MAX233 needs no external capacitors), but the board area
is smaller.

Best Wishes