STM3240G-EVAL & RS-232

[mailmail9116]

Posted on December 14, 2012 at 16:04

Hi,

I downloaded the evaluation firmware that came with the board,and tried to play with the RS-232 ,but it does not work.

I configured the baud and everything correctly both on the PC and on the eval board.

Can it be that the problem is with the cables? i used female serial rs232 gender changer like that

http://www.amazon.co.uk/Female-Serial-Gender-Changer-Adapter/dp/B000Q8FDAS

and a standard rs232 to usb converter...any ideas on what may be the problem?

Thanks

#rs232-tester

[Tesla DeLorean]

Posted on December 14, 2012 at 16:20

How is it wired, if it's straight through you'll have a problem.

You need a standard NULL MODEM cable

http://www.nullmodem.com/NullModem.htm

http://www.amazon.com/Serial-Modem-Cable-Female-RS232/dp/B002KDSMP0

[mailmail9116]

Posted on December 15, 2012 at 12:16

Okay,

But i still have to connect it to my pc , and for this i need the rs-232 to usb converter,can i connect it to the null modem cable?

thanks

[Tesla DeLorean]

Posted on December 15, 2012 at 13:27

That's the way these cables are designed to function. It would connect to the rear of a PC, or to a USB-to-Serial type adapter.

With like-to-like connectors, in this context, there is the need to cross-over the key lines TX<->RX, etc.

If you are concerned with how this works, or needs to work, I would direct you to look at the pin out configurations of the ST boards, and a PC/USB serial connections and draw flow lines between them. ie the TX on the sending board needs to get to RX on the receiving board.

Again, referring to the schematic you should observe RS232 line drivers, which convert to-from the CMOS 3V levels to RS232 compatible levels. This permits the direct connection to other serial devices. One might be careful about 1980's era devices as the connectoring and pin utilization, and flow control, were far less consistent. When in doubt refer to documentation, or get out a scope/meter and probe out the signals.

[Andrew Neil]

Posted on December 15, 2012 at 14:00

''When in doubt refer to documentation, or get out a scope/meter and probe out the signals''

 

Indeed.

You really need something like this:

See:

http://www.chipkin.com/rs-232-mini-tester/

for some suggestions

[Tesla DeLorean]

Posted on December 15, 2012 at 14:47

Back in the day I had one of these

http://www.flickr.com/photos/pnt103/6074303957/