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

Jnana Panuganti
Associate II
Posted on June 05, 2017 at 17:53

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?

 

#bootloader #stm32-can
3 REPLIES 3
Posted on June 05, 2017 at 19:16

>>Is it better to implement a custom firmware upgrade method?

Generally yes, because you designed the board and know what components you used, etc. The System Loader is best reserved for situations where your own loader or the system gets bricked for some reason.

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Posted on June 15, 2017 at 23:51

Thanks Clive!

I was just wondering if someone at ST can clarify what does the footnote mean by 'temperature or other conditions'?

Is there a range where this is guaranteed to work?

Posted on June 16, 2017 at 14:14

Hi,

If the HSI accuracy impacted by the temperature or other HSE detection, it will not be done correctly and the CAN baudrate will not be correct.

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Thanks
Imen