Verify in bootloader USART protocol fails

[TomKing]

Hello Community,
Using the USART commands in boot mode on a STM32H723 CPU, I faced following issues:
Extended erase (0x44) and writing memory(0x31) to the flash works fine, if I write ALL bytes in blocks of 256 bytes.
But if I do a read memory(0x11) after writing one block for verify purposes, I get FFs on the first bytes instead the correctly written data. This happens exactly after the second read block always, even if I write 4 blocks and do the readback then.
The STM32 CubeProgrammer also only supports verification AFTER writing all data to the flash, not block by block.
Is this a generic limitation in the boot loader ?

[FBL]

Hi @TomKing 

You can simply write the same 32 bytes instead of dummy bytes. These workarounds will be documented in the AN2606. 

You are welcome and happy Holidays.

[TomKing]

Hello @FBL 

I wonder if the manual verify (re-reading the data) after command WriteMemory 0x31 is necessary at all ?

If the boot loader already checks the written data and sends a NACK in case of deviations, I can omit this step.

How safe is it to rely on the WriteMemory return value ?

Thank you in advance.

[Pavel A.]

> How safe is it to rely on the WriteMemory return value ?

Not safe. Read back & compare.

[FBL]

Hello @TomKing 

According to USART protocol in AN3155, figure 13, the ACK byte sent by the bootloader after a successful write operation indicates that the data has been written correctly not being read. 

So, you need to read it back.

[TomKing · Accepted solution]

Hello All,
I've implemented the verify with the described workaround in our company tool. Works as expected now. Thanks to everyone who helped to solve this !