UART Rx Interrupt Routine for Variable-Length Data on STM32F072RBT6

[shyamparmar]

I’m currently working with the STM32F072RBT6 microcontroller and trying to implement a UART receive interrupt routine for handling variable-length data. My goal is to receive different application .bin files over UART in interrupt mode. However, the challenge I’m facing at uart receive interrupt function because receive file size is not fixed.  

HAL_UART_Receive_IT(&huart3,(uint8_t *)buffer,8032);

Thank you in advance for your help!.

[Andrew Neil]

Set the receive size to 1 - receive 1 byte at a time.

Doing it with HAL_UART_Receive_IT is quite an overhead, but it can work - depends on how fast you want/need it to be...

[Tesla DeLorean]

You'll need to manage as bytes or blocks, or create circular/ring buffers where you consume the data elsewhere. 

For files, where size is imparted, look at Y-MODEM 

[shyamparmar]

@Andrew Neil  Thank you for the suggestion to receive 1 byte at a time using HAL_UART_Receive_IT. I understand that this approach can add overhead, but it might work for my use case. However, I’m still unclear about how to determine the end of the file.

Since I will be receiving the file byte-by-byte, how can I know when I have received the complete binary file so I can proceed with writing the data to flash and jumping to the application?

[Andrew Neil]

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@shyamparmar wrote:

I’m still unclear about how to determine the end of the file.

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well, that's an entirely different question - nothing to do with the UART handling of the bytes!

As @Tesla DeLorean suggested, you will need some sort of protocol to handle that - X/Y/Z-modem are specifically designed for this very application, and are widely supported by terminal software.

https://web.cecs.pdx.edu/~rootd/catdoc/guide/TheGuide_226.html

https://en.wikipedia.org/wiki/XMODEM

https://en.wikipedia.org/wiki/YMODEM

https://cambium.inria.fr/~doligez/zmodem/ymodem.txt 

ST Use Y-modem in their IAP Application Note - AN4657, STM32 in-application programming (IAP) using the USART:

https://www.st.com/resource/en/application_note/an4657-stm32-inapplication-programming-iap-using-the-usart-stmicroelectronics.pdf

[Tesla DeLorean]

>>Since I will be receiving the file byte-by-byte, how can I know when I have received the complete binary file so I can proceed with writing the data to flash and jumping to the application?

You'd have to impart the size in header information, or embedded in the image itself.

[Karl Yamashita]

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Since I will be receiving the file byte-by-byte, how can I know when I have received the complete binary file so I can proceed with writing the data to flash and jumping to the application?

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Well it depends on how much ram you have, but you'll probably want to receive data in chunks and save to flash memory. Then request for another chunk and so on. 

See this pdf to get a general idea

https://www.st.com/resource/en/application_note/an3155-usart-protocol-used-in-the-stm32-bootloader-stmicroelectronics.pdf

[zhaowhong]

I just wrote this program a few days ago. You should use DMA to receive data.Regularly query data and receive data for splicing。And my bin file transfer added crc check