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STM32L4 XMODEM using USB CDC Interface

Question asked by kenney.jacob on Feb 3, 2017

I'm trying to implement an XMODEM file transfer through the USB CDC Interface on an STM32L4 processor in Full-Speed and seem to be having issues with XMODEM 132 byte packets getting split up and one of the middle packets getting resubmitted. I need to be able to NAK/ACK the XMODEM packets to keep the transfer going but this seems to sometimes mess up the submitting of the sub-packets causing me to get invalid data. Is there anyway to only trigger the CDC_Receive_FS function once all 132 bytes are received at the end point? Handling the separate packets from within the CDC_Receive_FS is causing problems because sometimes the broken up packets are being sent multiple times and there is no easy way of detecting a repeat.

 

I generated my code using the latest STM32 firmware for STM32CubeMX and am working in Keil.

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