2 wire to 1 wire RS232 and vice versa - Electronic Circuits Projects Diagrams Free

Scarr · 27th August 2008, 09:44 PM

Hi,

I have a MCU with hardware RX+TX lines, I want to make these into a single RX/TX line with open collector outputs so I can connect to a multidrop bus.

I do have a circuit using NPN+PNP transistorsa that works but it echos everything I send back to MCU and its not a single chip soltuion as I'd really like, anyone point me at a nice small IC they know that fit's the job? or tell me what sort of IC I should be looking for?

P.S. TTL Levels

Thanks

Steve

Mike, K8LH · 28th August 2008, 12:24 AM

Hi Steve,

Just throw away the echo Rx character each time you transmit a byte. I've done this on both the PC side and on the MCU side without problem and with very little overhead. As you've noted, the echo character is only a concern when you're transmitting characters.

Mike

Scarr · 28th August 2008, 12:35 AM

Mike,

I am throwing chars away currently but as there are lots of places where I send characters it's a lot of code overhead, I thought there would be a way of sorting (blocking) the RX when TX'ing using a line driver / buffer or something

Thanks

Mike, K8LH · 28th August 2008, 12:38 AM

I throw away the echo Rx character in my low level driver. It takes something like three instructions (assembly). How are you doing it?

Mike

rezer · 28th August 2008, 04:56 AM

How about this device?

http://datasheets.maxim-ic.com/en/ds/DS2480B.pdf

Scarr · 28th August 2008, 08:45 PM

Absolutly fantastic this is exactly what I was looking for, single IC, small footprint and all my hassle gone, thanks again.

P.S. Mike I'm using BASCOM AVR with thier built in routines so it's not as easy for me to dump echo, but thanks for help anyway.

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27th August 2008, 09:44 PM	(permalink)
Scarr	2 wire to 1 wire RS232 and vice versa Hi, I have a MCU with hardware RX+TX lines, I want to make these into a single RX/TX line with open collector outputs so I can connect to a multidrop bus. I do have a circuit using NPN+PNP transistorsa that works but it echos everything I send back to MCU and its not a single chip soltuion as I'd really like, anyone point me at a nice small IC they know that fit's the job? or tell me what sort of IC I should be looking for? P.S. TTL Levels Thanks Steve Last edited by Scarr; 27th August 2008 at 11:40 PM.

28th August 2008, 12:24 AM	(permalink)
Mike, K8LH	Hi Steve, Just throw away the echo Rx character each time you transmit a byte. I've done this on both the PC side and on the MCU side without problem and with very little overhead. As you've noted, the echo character is only a concern when you're transmitting characters. Mike

28th August 2008, 12:35 AM	(permalink)
Scarr	Mike Mike, I am throwing chars away currently but as there are lots of places where I send characters it's a lot of code overhead, I thought there would be a way of sorting (blocking) the RX when TX'ing using a line driver / buffer or something Thanks Last edited by Scarr; 28th August 2008 at 12:36 AM.

28th August 2008, 12:38 AM	(permalink)
Mike, K8LH	I throw away the echo Rx character in my low level driver. It takes something like three instructions (assembly). How are you doing it? Mike

28th August 2008, 04:56 AM	(permalink)
rezer	How about this device? http://datasheets.maxim-ic.com/en/ds/DS2480B.pdf __________________ "Remember, you're special.....just like everyone else."

28th August 2008, 08:45 PM	(permalink)
Scarr	Rezer your the man :) Absolutly fantastic this is exactly what I was looking for, single IC, small footprint and all my hassle gone, thanks again. P.S. Mike I'm using BASCOM AVR with thier built in routines so it's not as easy for me to dump echo, but thanks for help anyway.