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STM32F7 CAN Transmit IT Flags

Question asked by Banciu.Alexandru on Apr 29, 2017

Hello guys,



The problem appears on CAN2 (don't know yet if it appears on CAN1 or CAN3).

I'm using HAL_CAN_Transmit_IT() to send data.

In the CAN2_TX_IRQHandler() I call HAL_CAN_IRQHandler().



1. Send 1 CAN frame on mailbox0.



1. When the TX Interrupt is entered, the CAN_TSR register doesn't show the flags: RQCP0 and TME0 as beeing set. 

2. The RQCP0 and TME0 flags are set, but it seems with a pretty high delay from executing the TX Interrupt.

3. The documentation "RM0410 -> STM32F76xxx and STM32F77xxx" specifies that the TX Interrupt is triggered when flags: RQCPx is set while TMEIE bit is enabled.



1. Question: How does the CAN TX Interrupt gets triggered without RQCPx set in the CAN_TSR? 



1. Send one CAN frame and check the CAN_TSR for available mailboxes, after exiting the TX Interrupt. 

I found the following pattern of free mailboxes:

(each number represents tx free mailbox that is going to be used for sending the frame)

0000101010101 | 0000101010101 | 0000101010101 | 0000101010101