STM32L476 CAN Bootloader

[sudo112358]

Hi,

we want to use the built-in CAN bootloader of a STM32L476. We experienced some strange behaviour while testing with a nucleo board, which we could partly fix.

First of all, after a write command, sometimes two ACK are sent, the data is also written twice in memory (once in the correct adress and a second time in the next adress). This behaviour has been almost fixed with some modifications, the power supply does seem to be unstable during flash operations, some larger bypass capacitors on the mcu's power pins helped :)

Because of a second issue (which would be too much to explain for now), I found the errata sheet for this controller. It says the following regarding the bootloader:

2.3.4

Bootloader: SPI and CAN

interfaces are not supported

Description

The bootloader does not support yet SPI and CAN interfaces.

Workaround

None.

Well...thanks. How should I interpret this? Is it known that the bootloader with CAN interface is not working - obviously we connected to the bootloader, so at least there is something present? Or that it somehow does something but occasionally crashes? Is it planned to fix the problems?

Greetings,

Christian

[Tesla DeLorean]

>>Is it planned to fix the problems?

For commercial projects you should discuss time lines and part availability with sales and FAE supporting your account. Where system loader versions are important care would be needed in ordering/sourcing of parts and knowing week numbers when changes were effected.

[sudo112358]

Hi,

it is not really a question about time lines, more about whether this is really a physical problem in the ROM, the layout/schematic of the nucleo (adding capacitors reduces the errors) or something else. Additionally, the information from the errata is confusing, especialls when considering UM1724 which says under 5.4 NUCLEO-L476RG boot loader limitations that there were limitations in bootloader version 9.0 (date code until week 22 of 2015) but these limitations would no longer exist in later versions (starting with date code week 23 of 2015). Bootloader Version 9.2 should support CAN bus, also from our tests it does somehow...the errata says "not supported". Somehow we managed to program without an error today, sometimes we still get the error of two ACK messages and the data being written twice.

Quite confusing, that's why I asked if someone else had these problems, possibly also with other mcu's. We are still in early developement, so we could change the mcu if we had the information that it is running on a different but comparable one.

Greetings,

Christian

[Tesla DeLorean]

The FAE's are more likely to have fielded such questions already. The people who could provide clear and definitive answers are not on the forum.

[sudo112358]

Hi again,

ok, now I understand. I will file a Support request. Thanks!

Greetings,

Christian