3.2.2.4. MCAN

Introduction

The Controller Area Network is a serial communications protocol which efficiently supports distributed real-time control with a high level of security. The MCAN module supports bitrates up to 5 Mbit/s and is compliant to the ISO 11898-1:2015. The core IP within M_CAN is provided by Bosch.

This wiki page provides usage information of M_CAN Linux driver.

Setup Details

TI board List

SoC

Board

Number of Instances

Connection Type

Enabled by default

Dra76x

EVM

1

Header

Yes

AM654x

IDK

2

DB9

Yes

AM64x

EVM

2

Header

Yes

AM62x

SK

3

Header

No

J721E

EVM

4

Header

Yes

J7200

EVM

4

Header

Yes

J721S2

EVM

5

Header

Yes

J784S4

EVM

6

Header

Yes

Table: Boards M_CAN Driver is Validated on

Notice for AM62x:

The AM62x SK does not carry a transciever to experiment with. The SoC does support CAN-FD, but it is required to connect a CAN external transceiver to the AM62x SK to test the full CAN functionality. Go to the following guide: How to enable MCAN in Linux for an example for connecting a CAN external transceiver to the AM62x SK.

CAN Utilities

There may be other userspace applications that can be used to interact with the CAN bus but the SDK supports using Canutils which is already included in the sdk filesystem.

Note

These instructions are for mcu_mcan0. If the board has multiple CAN instances enabled then they can be referenced by their CAN dts node names just like mcu_mcan0 here. For example, 2nd instance of CAN in the main domain ( ie main_mcan2 as referenced in the dts ) will be visible as main_mcan2 to the users.

Quick Steps

Initialize CAN Bus

  • Set bitrate

$ ip link set mcu_mcan0 type can bitrate 1000000

  • CAN-FD mode

$ ip link set mcu_mcan0 type can bitrate 1000000 fd on

  • CAN-FD mode with bitrate switching

$ ip link set mcu_mcan0 type can bitrate 1000000 dbitrate 4000000 fd on

Start CAN Bus

  • Device bring up

Bring up the device using the command:

$ ip link set mcu_mcan0 up

Transfer Packets

Cansend

Used to generate a specific can frame. The syntax for cansend is as follows:

<can_id>#{R|data}          for CAN 2.0 frames
<can_id>##<flags>{data}    for CAN FD frames

Some examples:

  1. Send CAN 2.0 frame

$ cansend mcu_mcan0 123#F00DCAFE

  1. Send CAN FD frame

$ cansend mcu_mcan0 113##2AAAAAAAA

  1. Send CAN FD frame with BRS

$ cansend mcu_mcan0 143##1AAAAAAAAA

Cangen

Used to generate frames at equal intervals. The syntax for cangen is as follows:

cangen [options] <CAN interface>

Some examples:

  1. Full load test with polling, 10 ms timeout

$ cangen mcu_mcan0 -g 0 -p 10 -x

b. fixed CAN ID and length, inc. data, canfd frames with bitrate switching

$ cangen mcu_mcan0 -g 4 -I 42A -L 1 -D i -v -v -f -b

Candump

Candump is used to display received frames.

candump [options] <CAN interface>

Example:

$ candump mcu_mcan0

Note: Use Ctrl-C to terminate candump

Further options for all canutils commands are available at https://git.pengutronix.de/cgit/tools/canutils

Stop CAN Bus

Stop the can bus by:

$ ip link set mcu_mcan0 down

Note

The earlier CAN naming convention had can0 referring to the first probed CAN instance and can1, can2.. and so on, to the other CAN instances in the order in which they are probed. For example, 2 CAN instances will have names as can0 and can1 assigned to them in the linux kernel, based on the order in which they are probed and irrespective of their CAN instance number. If the earlier CAN naming convention is needed, you can revert cfc97aeb022ddc03f252deebc9021aff449b24c8 commit in meta-arago repository.