CAN/FDCAN expert and can help on other topics but I cannot help on everything. So, please don't ask questions through private messages and be pushy to have an answer. I cannot serve all the questions as there are tens of them per day and I'm doing my best to help you in efficient way and keep the conversations in the forum ONLY. If I have the answer, I will not hesitate to provide it in the community thread. Many community members with high level skills can also help you. No need to tag ST employees to exclusively waiting an answer from them. Please also note that we provide a support in the limit we can give: we are not here to do your job for you. PS1: Sorry, I don't support issues on fake STM32 MCUs on Blue/Black.. other "colorful" pill platforms. Please purchase boards with GENUINE STM32. PS2: For direct access to the registers implementation please inspire from the HAL and compare it to your implementation. It's not easy to follow line by line your bit shifting, bit masking..