This is in reference to [STM32 HAL\_CAN\_Transmit always returns TIMEOUT (HAL\_CAN\_STATE\_TIMEOUT)](https://electronics.stackexchange.com/questions/334970/stm32-hal-can-transmit-always-returns-timeout-hal-can-state-timeout) 

We are in the process of setting up a similar environment, and at first draft, facing the same timeout-issue while sending CAN-packet, and thus landed on the above page. 

As a first question, are 2 (CAN) controllers always needed in the STM32F0 ecosystem for CAN-transmit to work? If yes, is it the CAN-standard, or just the way STM32F0-ecosystem works? 

Sorry if I am being too noob.  

Would be grateful for insights from experts :)