Serial I/O not getting input

Hi,

I am attempting to communicate with an XBee radio through Matlab serial, and while I am able to send data successfully, I am having trouble getting anything from the input.

For example, I can send a message with the following code to a terminal program connected to a matched XBee radio:

s = serial('COM8');
fopen(s);
fwrite(s,'TestMsg');

However, if I send a message from the same terminal that received the Matlab message, I cannot detect the message in Matlab using fscanf(s), or setting up a bytesavailable event with:

s.BytesAvailableFcnMode = 'byte';
s.BytesAvailableFcnCount = 1;
s.BytesAvailableFcn = @instrcallback;

I know the message is going through the radios because if I connect to the same serial port with a another terminal program (PUTTY or X-CTU) it shows up, so it seems like the problem must be with Matlab.

Thanks for any help!

Answer 1

[Gabriel Ryan]

Actually I just figured out what was wrong. The XBee default configuration uses RTS flow control, so the XBee was not sending the data because Matlab wasn't asserting RTS. X-CTU on the other hand has an option to assert RTS that is on by default and I can only assume PUTTY also asserts RTS.

I hope this helps anyone else who runs into similar problems.

[Gabriel Ryan]

(I fixed the problem by configuring the XBee radio not to use RTS, but you could also just tell matlab to assert the RTS pin)

Answer 2

[Adi Mico]

Maybe you have to set the terminator.

http://www.mathworks.com/help/toolbox/instrument/terminator.html

[Gabriel Ryan]

Adi, thank you for your response.

I just tried setting the terminator to 13, which is what both PUTTY and X-CT interpret for <return>, and also 10 (which I think is default anyway), but still did not see anything when I tried to use fscanf or set up a bytesavailabe terminator triggered event.