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Why CAN packets are not seen on CAN_TX pin in LS1021A?

Question asked by SUKRUTH RAMESH BABU on Sep 26, 2017
Latest reply on Oct 3, 2017 by Pavel Chubakov

Hello ,


Trying to develop CAN driver for LS1021A custom board.


Here are the steps followed,


1. Hardcoded RCW settings are loaded for board bringup and it is customized to enable CAN3_TX, CAN4_TX, CAN3_RX , CAN4_RX. (By referring to LS1021A reference manual, Bits 419-421 as 010  )

2. Initialized MCR , CTRL(for 1 Mbps speed) and Message Buffers in FlexCAN module as mentioned in the manual.

3. Transmit Process and Receive process are implemented with MB8 configured as transmit buffer , MB9 configured as receive buffer.


Here is my observation(as seen from the debugger),


Once transmit MB is set to ACTIVE state , it is participating in the arbitration process and transmitting the CAN packet .

After each successful transmission , IFLAG bit for MB8 is set and time stamp field of MB8 is being updated (can be observed in the debugger).


Now the question is,


Although transmission activity can be seen in the corresponding MB , Why there is no activity / CAN frame on CAN TX pin of the transceiver ?