XMODEM protocol for file transfer

[pvall.1]

Hi,

I'm currently working on file transfer through the XMODEM protocol, and I want to implement the logic in STM32CubeIDE. If anyone has already implemented it, please share the source code. It would be helpful for me.

Thanks

[Pavel A.]

@pvall.1 Of course you can use any adapter from the TTL UART of the STM32 to a PC. For a modern PC that does not have RS-232 ports, TTL to USB adapter is the best choice. If compatibility with RS-232 is needed, use a passive TTL to RS-232 adapter.

[elKarro]

If on the other side you're using TeraTerm, I suggest to develop your MCU counterpart from TeraTerm source code.
Remember: from the TeraTerm serial connection, you always receive a stream of bytes in open chain, so you have to write your own parser to scan the received bytes and detect XMODEM packets. I remark this since I don't know your experience with pure UARTs, maybe you're expecting to receive something structured, i.e. like an udp datagram.

[pvall.1]

Hi,

I utilized the above code and changed it as per requirements. I am able to receive one packet correctly with a matching CRC value. However, when I send an ACK or NAK from the receiver end, the sender is not sending the second packet. What could be the possible reason?

[Andrew Neil]

Your ACK or NAK must be incorrect in some way.

Try capturing the traffic from a "good" transfer, and compare with a failing one ...

Does the sender give any error details to help?

Have you tried with any other sender(s)?

[pvall.1]

The sender didn't provide any details like EOT or CAN. It's timing out and the X-Modem send popup disappears. After timing out, I'm able to see the NAK sent by the receiver in the command Prompt.

[Pavel A.]

Have you seen one of Ymodem examples from ST? they have Ymodem-1K in several examples and demo apps for several MCU models: IAP, SBSFU... It works well with latest Teraterm. Xmodem is older simpler protocol.