MATLAB: Serial I/O not getting input

serialserial communication interfaceserial port

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!

Best Answer

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.

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MATLAB: How to write bytes to a serial object – to send data over USB-serial XBee to Arduino

uint8 are bytes . You can fwrite() them directly.

MATLAB: Need help to encrypt and decrypt the RS232 serial port data

function send_encrypted(s, data_to_send)
  %s is to be a serial object, data_to_send is numeric
  data_as_bytes = typecast(data_to_send, 'uint8');
  encrypted_bytes = encrypt_bytes(data_as_bytes);
  cname = uint8(0 + class(data_to_send)); %chars to bytes
  cnamehdr = [uint8(length(cname)), cname];
  enchdr = uint16(length(encrypted_bytes));
  header = [cnamehdr, enchdr];
  fwrite(s, header);
  fwrite(s, encrypted_bytes);
end
function data = receive_encrypted(s)
  %s is the serial connection.
  cnamelen = fread(s, 1, 'uint8');
  cname = char(fread(s, cnamelen, 'uint8'));
  numencbytes = fread(s, 1, 'uint16');
  encbytes = fread(s, numencbytes, 'uint8');
  data = typecast( decrypt_bytes(encbytes), cname);  %turn it back to double
end
function enc = encrypt_bytes(bytes_to_encrypt)
  %magic encryption goes here
  enc = 255 - bytes_to_encrypt;  %this is the encryption
end
function decr = decrypt_bytes(bytes_to_decrypt);
  %magic decryption goes here
  decr = 255 - bytes_to_decrypt;  %this undoes the encryption
end

Extensions would be required to handle more than 65535 bytes of data per transmission, or to transparently handle strings during transmission, or if you wanted to send data with mixed data types.

By the way, you did know that the Zigbee support AES encryption in hardware, right?

Best Answer

Related Solutions

MATLAB: How to write bytes to a serial object – to send data over USB-serial XBee to Arduino

MATLAB: Need help to encrypt and decrypt the RS232 serial port data

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