How to send/recive txt file using RS232

Hi,

I'm working on some project with RS232 and I need to send text file using RS232. Can somebody explain me how to do it? Thanks!

[Jan]

Using Matlab or Simulink? Do you have the Instrument Control Toolbox?

[Roko]

Matlab, i have Instrument Control Toolbox

Answer 1

[Walter Roberson]

The old xmodem file transfer protocol is very easy to write. zmodem was a lot more efficient but more difficult to write, but likely you could find source in C somewhere. For more complex requirements like file serving, consider using c-kermit -- a much larger package but well designed and quite robust.

Or you could go for SLIP or PPP and use them to run IP over serial, allowing you to use programs such as FTP or SCP.

[Roko]

Tnx, can I do it in matlab ( write script for file transfer )?

[Walter Roberson]

As I mentioned before, xmodem is very easy to write. The hardest part of it in Matlab is doing the timeouts on reading data, and that isn't all that difficult.

[Brian]

I know this is an old thread, but I am trying to do something similar. I have a *.img file that I am trying to send via RS-232 using the xmodem FTP, but I'm not exactly sure how to go about it. You said it's very easy to write, but I have no experience with this side of MATLAB. Would you be able to point me to an example of something similar?

My initial feel is that I would fopen the *.img file, use this function, and transmit crc via

write(serialdevice,crc,??)

Is this correct? Any help you could provide would be helpful. Thanks.

[Walter Roberson]

https://pythonhosted.org/xmodem/xmodem.html has Python code for xmodem

https://en.m.wikipedia.org/wiki/XMODEM contains the protocol description

You can write() uint8 data

In order to send data that is not uint8, typecast() numeric data to uint8. For character data you cannot typecast to uint8, so either cast() to uint8 or (better) use native2unicode() and unicode2native() which will allow you to send characters beyond ascii 255

[Brian]

Success! Wrote this over the weekend and was able to finally test it last night. The one hiccup I had was that the CRC-16 calculator I referenced above outputs the 16-bit crc in little-endian, while XMODEM expects it in big-endian. Thanks for your help!

[Walter Roberson]

It doesn't really matter whether you use big-endian or little-endian as long as the two sides are consistent.