MUX/DEMUX Circuits

[Jerrya13]

Need MUX circuits to handel 40 to 50 inputs.Carried over RS232 wiring. To be DEMUXed with the same number outputs.
Inputs not data string only two states (0) or (1).End results to control LED's and relays corresponding to input positions.

 

[melone]

Isn't RS232 only 9 wire?

 

[nbucska]

What is the distance and required data rate ?

<nbucska@pcperipherals.com>

 

[automatic2]

if your set on the 232 protocol, you might as well use a baby AT motherboard on both ends. An old 286 will be fine. piggy back a couple of PPIs with required address decode and you'll have plenty of ports for software muxing. The old XT boards might even be easier as they had already decoded out an address space and have an extra rom socket if you want to drop in your firmware. The exsisting bios has all your comm functions, and you'll have the option of monitoring your I/Os. You may want to consider opto isolation if your in an industrial enviroment.

 

[lhatch]

I would get 4 AVR Mega8 chips, 2 for input side and 2 for output (LED) side. There are, I think, 23 I/O pins. Make one TX on one pair, and other (output side) make one pin of each chip RX. Write a program to read 22 inputs, and send a bit pattern via RS232 of the input pair to the output pair. I say pair, since you have 22 pin on a chip you can use and you need 40+. That would give you 44 inputs, 2 RS232 signals to 44 OUTPUTS. Only requiring 4 wires, POWER, GROUND, DATA1 (TX1/RX1) and DATA2 (TX2/RX2).

I would use RVKBASIC to write the software. But that would be my approch.

 

[porage]

I too would like to build a similar circuit but would like to use 74LS153 integrated circuit chips but need to know how to wire them to achieve up to 100 inputs to be carried over RS 232 lines. Inputs only two states also. Any ideas?

 

[lhatch]

If you used the 74153 or 74154 you will still need logical to do the RS232, that is why I like the Mega8. It has all the IO lines on the chips and you use one for the RS232 communications.

 

[Jerrya13]

Keeping it simple would someone show me how to wire the AVR Mega8 chips to except 40 to 50 high or low inputs, transmit these inputs via a single RS232 cable to a simular chip set that will give a high or low output corrosponding to the same position inputs. The programing can come later.

 

[skills]

Ditto on using Atmel AVR with BASCOM demo compiler from

http://www.dontronics.com

and download the AVR datasheet on a mega8535 or 8515.

 

[lhatch]

I mentioned the Mega8, there might ne AVRs with more IO lines.

You wire the data pins to your relays, or relay drivers. I would rob one of them to communicate with the chip. Lets say there are 23 I/O pins, wire 22, and one will be the RS232 input. Then write a program to monitor that pin in RVKBASIC (

http://www.bastoc.com).

Then send 3 bytes on the buss (you can use less). 11O, chip 1, pin 1 ON, or 23F chip 2, pin 3 OFF.

On the BASCOM question, try RVKBASIC, it is free and I have used it with great sucess.