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I’m attempting to flash code over CANBUS on a Nucleo-F446 board, using the instructions from the following application note:
[CAN Protocol Used in the STM32 Bootloader](https://www.st.com/resource/en/application_note/cd00264321-can-protocol-used-in-the-stm32-bootloader-stmicroelectronics.pdf).
According to the document, in Boot mode, the default CAN baud rate is 125 KBPS, and the CAN2 pins (PB5 and PB13) should be used.
For testing, I sent a CAN message with DLC=0 and STDID=0x79, expecting an acknowledgment (ACK) from the STM32 with the same ID (0x79). However, I’m not receiving any response from the device.
In my setup, I’m using an external CAN transceiver like the MCP2551 or SN65HVD230, as the Nucleo-F446 lacks an onboard transceiver. The CAN bus is properly terminated with 120-ohm resistors at both ends. I’ve ensured the baud rate is configured to 125 KBPS, as required in bootloader mode. The STM32 is in bootloader mode, with the BOOT0 pin set high and the device reset. The CAN message is formatted with DLC=0 and STDID=0x79, but no acknowledgment is being received.
Could you help me understand what might be going wrong with my setup or if I’m overlooking anything crucial?
Check the CAN2 pin configuration on your Nucleo-F446 board. Ensure PB5 (CAN2_TX) and PB13 (CAN2_RX) are correctly connected to the external transceiver (MCP2551/SN65HVD230). Verify the transceiver’s VCC and GND connections.
Also, confirm the bootloader mode is properly activated by monitoring the STM32’s BOOT0 pin and reset sequence.
Are you using a CAN bus analyzer or sniffer to verify the CAN message is being transmitted correctly and not corrupted?
Most times you need to verify the voltages required for setup, i use one CAN transciever and i discovered it had two voltage rails. So confirm this
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