Using the Programming Serial Port for I/O

VEX V5 General Discussion Technical Discussion
1

I am trying to use the Rj-14 Serial Port on the Vex for I/O (the serial port used for programming the vex). Everything works fine if I use the Programming module, but I want to be able use a RS-232 to TTL cable. When I try to use the rs232 to ttl cable, it doesn’t work unless attach the serial cable to the Vex after I power on the Vex. The only thing I can figure is that I don’t have the Com port initialized correctly. Any one know what I need to do to get this working??

2

Is the Com port a real Com Port or a USB to Serial??

What Operating System are you using??

What PC Application are you using to Initialize the Com Port??

It sounds like you are using a 3rd Party RS-232 to TTL converter?? What brand is it or what Chip Set does it use (e.g. B&B or Maxim 220-243 Family)??

What other Trouble-Shooting steps have your tried??

3

Its a RS-232 -to- TTL converter from Superdroid (sorry, I cannot find the chipset). Using an actual serial port on Windows XP and its a program that I wrote. I turned off all flow control.

Tried clearing the buffers.
Tried enabling flow control.
Tried crossing the RX and TX … Thought I might have had them backwards.

4

the chipset is MAX3232C

5

Think I figured it out, I swapped the CTS and RTS lines and it seems to work now

6

I am glad it was so simple…

On the Vex Programming Cable, the CTS/RTS seem to be used for toggling the Programming Mode… You won’t need them for basic commands to and from the Vex Controller…

7

New problem.

Same Rs232-to-TTL cable, trying to communicate through the TX/RX TTL Serial Port (in the Analog/Digital block). Works fine though the programming cable, doesn’t work at all with the Rs232-to-TTL cable. (If I print out what the Vex receives, it seems to only get the first and third bytes).

Is there something special in wiring this port?

8

AFAIK, it is the same type hardware as the Programming Port.

Is the BAUD RATE too high?? It sounds like it is dropping characters… Can you slow the Baud Rate down, to like 1200 or 2400bps?? Or try another RS232 to TTL converter, I use at my work a B&B converter.