3.2.2.5. 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
J721E	EVM	4	Header	Yes
J721S2	EVM	5	Header	Yes
AM62x	SK	3	Header	No

Table: Boards M_CAN Driver is Validated on

Connection Configuration

Header to Header	Header to DB9

Table: Various DCAN EVM Connection Configuration

Equipment

Female DB9 Cable

For boards exposing M_CAN using male DB9 connectors, a female connector is required. The other side can be male or female depending on the other CAN device the user connects to.

Jumper Wires

For boards where the CAN pins are broken out via a header, female jumper cables will be ideal for connection. The CAN pins will be CAN H (typically pin 1 of the header), GND (middle pin of the header) and CAN L (lowest pin on the header). The pinout in the header might vary across different boards and users must consult the board’s schematic to verify this.

Custom DB9 to Header Cable

Typically CAN devices use a DB9 connection therefore for boards whose CAN pins are broken out via a header it is helpful to create a header to DB9 connector cable. This custom cable is simple to make. Either a male or female DB9 connector (not cable) must be obtained along with three female jumper wires.

Snip one end of each of the jumper wires and expose some of the wiring. Now solder each of the exposed wires to pin 7 (CAN H), pin 2 (CAN L) and pin 3 (GND). Make sure your soldering on the side of the DB9 that has the metal lip meant to push some of the exposed wire into and soldering to the correct pins correctly. Use the below diagram as a reference.

Wiring Diagram	Example of completed cable.

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 can0 (first and perhaps only CAN instance enabled). If the board has multiple CAN instances enabled then they can be referenced by incrementing the CAN instance number. For example 2 CAN instances will have can0 and can1.

Quick Steps

Initialize CAN Bus

• Set bitrate

$ ip link set can0 type can bitrate 1000000

• CAN-FD mode

$ ip link set can0 type can bitrate 1000000 fd on

• CAN-FD mode with bitrate switching

$ ip link set can0 type can bitrate 1000000 dbitrate 4000000 fd on

Start CAN Bus

• Device bring up

Bring up the device using the command:

$ ip link set can0 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 can0 123#DEADBEEF

2. Send CAN FD frame

$ cansend can0 113##2AAAAAAAA

3. Send CAN FD frame with BRS

$ cansend can0 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 can0 -g 0 -p 10 -x

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

$ cangen vcan0 -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 can0

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 can0 down