TMS320F28379D: How to process a received CANbus remote request as an ISR

Colin Bussiere

Tool/software:

Hello,

I would like to use the CAN bus peripheral to receive remote requests for around 60 different IDs and provide unique data messages back based on the requested ID. There isn't enough message objects (32) to do this with an auto reply, CAN_MSG_OBJ_TYPE_RXTX_REMOTE, as seen in can_ex9_remote_answer.c .

My thought is to create an ISR which 1) confirms the IRQ is caused by a remote request and 2) checks the ID of the remote request and replies with the associated CAN bus data frame. My questions are:

From within an ISR how can I check if the can bus message had the remote bit set (driverlib preferred) so I can distinguish between RX of a data frame vs a remote frame.
From within an ISR how can I obtain the ID used in the CAN bus message (identify which of the 60 different possibilities)?
Is using an ISR for replying to so many remote IDs the best approach or are there any other suggestions?

Thank you.

over 1 year ago

0 Colin Bussiere over 1 year ago

Prodigy 140 points

I have made some progress. With respect to the second bullet item, there is a driverlib function called "CAN_readMessageWithID" which can be used to select the correct reply data. Currently looking through the TRM for a register that may provide the remote bit state.

0 QJ Wang over 1 year ago in reply to Colin Bussiere

TI__Guru**** 200756 points

(+) [FAQ] TMS570LC4357: DCAN remote frame - Arm-based microcontrollers forum - Arm-based microcontrollers - TI E2E support forums

0 Mark Kharab over 1 year ago

TI__Prodigy 20 points

Hi, can you provide more clarification on the first question and the third question?

0 QJ Wang over 1 year ago in reply to Mark Kharab

TI__Guru**** 200756 points

Hi Mark,

The Remote message and response data message are handled by CAN Message Handler automatically. When a remote message is received, three different configurations of the matching message object are considered by the Message Handler.

1. DIR=1 and RmtEn = 1: the response data message is transmitted

2. DIR=1 and RmtEn = 0, and UMASK=1: the arbitration and control field are saved to the message object

3. DIR=1 and RmtEn = 0, and UMASK=0: The remote message is ignored.

You can use #2 configuration for your special use case.

1. Configure one message object #0 or mailbox: TX, TmtEN=0, and UMASK=1. The received remote message is stored in this message object

2. Read the arbitration and control fields: ID

3. Then transmit the message object with same ID manually

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TMS320F28379D: How to process a received CANbus remote request as an ISR