Pololu 23201a..please help

I just realized I was using hyperterminal at 9600 8-N-1 rather than 38400 8-N-1…

Have to wait till I get home to test again… im pissed I did that, but I have been studying like crazy for my cisco exam all month and that is 9600 lol. o well back to the breadboard tonight… i really hope this works.

Unfortunately, the baud rate should not have any affect on the loopback test, so I doubt that’s your problem. However, the loopback test on the cable alone is not a verification of your serial cable. Null modem cables have RX and TX internally swapped so that you can plug each end into a computer and have the two talk to each other. Since the loopback test involves shorting TX to RX on your cable, the test will pass even if the two pins are swapped. If you didn’t specifically avoid purchasing a null modem cable, it sounds like this could be your problem (or at least, very roughly speaking, there’s a 50% chance it’s your problem).

If you get a multimeter, you can test to see if you have the right cable by seeing if the RX and TX lines pass straight through (i.e. use the multimeter to make sure there is continuity from pin 2 on one end to pin 2 on the other (and while you’re at it, repeat the test for pins 3 and 5). The picture on this page shows you how the DB9 pins are numbered. If you have a null modem cable, pin 2 on one side will connect to pin 3 on the other, and vice versa.

While you’re picking up a multimeter, I suggest you try getting another cable that you know for sure isn’t a null modem cable. Even if your current cable is the right kind, there could be a problem with it (e.g. a loose connection somewhere).

- Ben

Still @ work

But I went to radioshack.com and this is the exact (im 99% positive as its the same brand and price) cable I bought and i am using. Does this look to you as a “null” cable? would it say it in the description if it was?

radioshack.com/product/index … id=prod_cs


That cable looks like it’s the right kind, though if there was a problem with the ground connection it wouldn’t be revealed by the loopback test.

When you get home, can you post a picture of your setup that lets me clearly see how everything is connected?

- Ben

Sorry It was a hassle tonight and i couldnt take the pictures. but i did test it with a multimeter and the breadboard connections were getting 5.17V and I STILL cannot get it to work. this is so frustrating