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Clarification regarding ST bootloader - CAN operation. (Foot note in AN2606)

Question asked by Jnana Panuganti on Jun 5, 2017
Latest reply on Jun 16, 2017 by Imen D

There is a footnote on page 20 that reads:


Note: For STM32 devices embedding bootloader using the DFU/CAN interface in which the external clock source (HSE) is required for DFU/CAN operations, the detection of the HSE value is done dynamically by the bootloader firmware and is based on the internal oscillator clock (HSI, MSI). Thus, when due to temperature or other conditions, the internal oscillator precision is altered above the tolerance band (1% around the theoretical value), the bootloader might calculate a wrong HSE frequency value. In this case, the bootloader DFU/CAN interfaces might dysfunction or might not work at all.


We are considering using ST's bootloader for in-field application. However this footnote has raised some concerns in our engineering team. We are using STM32L433 and ST32L496 micros in our system and our operating temperature will likely be between 15 to 40 deg C. 


How likely is this scenario to occur where a wrong HSE frequency is calculated? Also what are the "other conditions"?


Does anyone have experience using ST's bootloader over CAN in a commercial setting?


Is it better to implement a custom firmware upgrade method?