6.1.5. How to enable MCAN in Linux

The following guide applies to these devices:

  1. AM62x SK

  2. AM62SIP SK

  3. AM62x LP SK

  4. AM62Ax SK

  5. AM62Px SK

The following table shows a summary for MCAN support in TI SDK.

  1. “nx MCAN” => how many MCAN nodes are enabled in the device tree for a specific device.

  2. “+ overlay” => for a specific release and device combination, there exists this overlay to enable nx MCAN in the Processor SDK.

8.6

9.0

9.1

AM62x SK

1x MCAN + k3-am625-sk-mcan.dtbo overlay

3x MCAN + k3-am625-sk-mcan.dtbo overlay

3x MCAN + k3-am62x-sk-mcan.dtbo overlay

AM62SIP

n/a

n/a

3x MCAN + k3-am62x-sk-mcan.dtbo overlay

AM62x LP SK

1x MCAN

3x MCAN + k3-am625-sk-mcan.dtbo overlay

3x MCAN + k3-am62x-sk-mcan.dtbo overlay

AM62Ax SK

1x MCAN

3x MCAN

3x MCAN + k3-am62x-sk-mcan.dtbo overlay

AM62Px SK

n/a

n/a

4x MCAN + k3-am62p5-sk-mcan.dtbo overlay

6.1.5.1. MCAN Overview

The CAN-FD transceiver and CAN-FD controller make up a CAN node. A CAN-FD transceiver is the interface between the CAN-FD controller and the CAN bus. It translates the logic level messages from the CAN-FD controller into the CAN differential scheme on the CANH and CANL pins of the CAN-FD transceiver. The CAN-FD controller can be thought of as an MCU, the part of the CAN node that processes all the information to and from the CAN bus.

../../../_images/mcan-environment.JPG

For more information on MCAN, refer to TRM Peripherals -> Industrial and Control Interfaces -> Modular Controller Area Network (MCAN)

The Linux Kernel driver for MCAN can be found in <path-to-linux>/drivers/net/can/m_can.


6.1.5.2. CAN Transceiver

The AM62 SKs do not carry a CAN-FD transciever to experiment with. The SoC does support CAN-FD, but it is required to connect an external CAN-FD transceiver to the AM62x SK to test the full functionality of CAN. In this guide, we will connnect an external CAN transceiver (not CAN-FD capable) as shown in the figure below to test CAN functionality on AM62x SK.

The CAN transceiver tested is included in SN65HVD230 CAN Board Kit, which is the transceiver soldered into a breakout board which can be purchased here. If only the transceiver needs to be purchased, it can be purchased in Digi-key, or Mouser Electronics.

../../../_images/mcan-external-transceiver.jpg

6.1.5.3. Connections

6.1.5.3.1. AM62x:

There is 1x MCAN in the MAIN domain and 2x MCAN in MCU domain. According to the AM62x datasheet on Table 6-1. Pin Attributes we can see the following Ball Names of interest:

  1. MCAN0_RX

  2. MCAN0_TX

  3. MCU_MCAN0_RX

  4. MCU_MCAN0_TX

  5. MCU_MCAN1_RX

  6. MCU_MCAN1_TX

../../../_images/mcan-pin-attributes.JPG

Ex: Pin attributes for MCAN0 (MAIN domain MCAN)

On the AM62x schematics, SOC - General, User Expansion Connector, and MCU Header we can see the following:

  1. MCAN0_RX becomes signal name EXP_UART5_TXD

  2. MCAN0_TX becomes signal name EXP_UART5_RXD

  3. EXP_UART5_TXD is pin 8 on User Expansion

  4. EXP_UART5_RXD is pin 10 on User Expansion

  5. MCU_MCAN0_RX is brought out by pin 22 on MCU Header

  6. MCU_MCAN0_TX is brought out by pin 16 on MCU Header

  7. MCU_MCAN1_RX becomes signal name MCU_GPIO0_16

  8. MCU_MCAN1_RX becomes signal name MCU_GPIO0_15

  9. MCU_GPIO0_16 is brought out by pin 11 on MCU Header

  10. MCU_GPIO0_15 is brought out by pin 10 on MCU Header

../../../_images/mcan-schematic-soc-general.JPG ../../../_images/mcan-schematic-user-expansion.JPG ../../../_images/mcan-mcu-header.JPG

Schematic: SOC - General

Schematic: User Expansion Connector

Schematic: MCU Header

In summary:

  1. MCAN0_RX is brought out on pin 8 on User Expansion

  2. MCAN0_TX is brought out on pin 10 on User Expansion

  3. MCU_MCAN0_RX is brought out on pin 22 on MCU Header

  4. MCU_MCAN0_TX is brought out on pin 16 on MCU Header

  5. MCU_MCAN1_RX is brought out on pin 11 on MCU Header

  6. MCU_MCAN1_TX is brought out on pin 10 on MCU Header

6.1.5.3.2. External CAN Transceiver:

The CAN external transceiver used in this project is SN65HVD230 CAN Board. The schematic for this CAN board is the following:

../../../_images/mcan-schematic-external-transceiver.PNG

  1. Pin 1 on Header 4 is CAN_TX

  2. Pin 2 on Header 4 is CAN_RX

  3. Pin 3 on Header 4 is DGND

  4. Pin 4 on Header 4 is 3.3V

  5. Pin 1 on Header 2 is CANL

  6. Pin 2 on Header 2 is CANH

6.1.5.3.3. AM64x EVM:

There are 2x MCANs MAIN domain, MCAN0 and MCAN1. On the AM64x GP EVM User’s Guide section 3.4.14: CAN Interface and CAN INTERFACE section on the AM64x schematics, we can see the following:

  1. MCAN0_H is brought out by pin 1 on J31 connector

  2. MCAN0_L is brought out by pin 3 on J31 connector

../../../_images/mcan-schematic-can-interface.JPG

Schematic for AM64x GP EVM - CAN Interface for MCAN0

6.1.5.4. Testing 1x MCAN on AM62x and 1x MCAN on AM64x

AM62x Hardware Setup

To test the MCAN0 on AM62x SK, we are using the CAN-FD controller on the AM62x and 1x external CAN transceiver, which completes one node on the CAN bus. Connect the CAN transceiver to AM62x as shown in the following diagram:

../../../_images/mcan-diagram-am62x-transceiver-am64x.png

  1. AM62x pin 8 (MCAN0_RX) on User Expansion to pin 2 (CAN_RX) on the CAN transceiver Header 1

  2. AM62x pin 10 (MCAN0_TX) on User Expansion to pin 1 (CAN_TX) on the CAN transceiver Header 1

The CAN external transceiver will then need to be powered, connect 3.3V and GND pins to a reliable power supply.

AM64x hardware Setup

Now connect AM64x EVM to receive CAN packages from AM62x according to the following diagram:

../../../_images/mcan-diagram-evm-to-evm.png

  1. CAN transceiver pin 1 (CANL) on Header 2 to pin 3 (MCAN0_L) on AM64x J31 connector

  2. CAN transceiver pin 2 (CANH) on Header 2 to pin 1 (MCAN0_H) on AM64x J31 connector

Final Setup

The following images shows the final setup for testing 1x MCAN on AM62x and 1x MCAN on AM64x:

../../../_images/mcan-test0.JPG ../../../_images/mcan-test1.JPG

AM62x and external transceiver

AM64x receving CAN packets from AM62x

With all boards powered on and booted to Linux kernel, the following commands could be executed to test CAN functionality.

Listing 6.1 MCAN0 on AM64x to display received CAN packet
root@am64xx-evm:~# ip link set can0 down
root@am64xx-evm:~# ip link set can0 type can bitrate 125000
root@am64xx-evm:~# ip link set can0 up
[   40.940389] IPv6: ADDRCONF(NETDEV_CHANGE): can0: link becomes ready
root@am64xx-evm:~# candump can0
[   47.533511] can: controller area network core
[   47.538112] NET: Registered protocol family 29
[   47.555073] can: raw protocol
can0  123   [4]  DE AD BE EF
[  138.824591] Initializing XFRM netlink socket
[  140.303978] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[  140.321844] Bridge firewalling registered
[  141.457406] process 'docker/tmp/qemu-check709863015/check' started with executable stack

Note: Use Ctrl-C to terminate candump

Listing 6.2 MCAN0 on AM62x to send CAN packet
root@am62xx-evm:~# ip link set can0 down
root@am62xx-evm:~# ip link set can0 type can bitrate 125000
root@am62xx-evm:~# ip link set can0 up
root@am62xx-evm:~# cansend can0 123#DEADBEEF
[ 1392.577915] can: controller area network core
[ 1392.582388] NET: Registered protocol family 29
[ 1392.594650] can: raw protocol

For more documentation on using the CAN utilities software, go to MCAN.

6.1.5.5. Testing 3x MCAN on AM62x

To test the 3x MCANs, connect 3x external CAN transceivers to each MCAN on AM62x:

  1. AM62x pin 8 (MCAN0_RX) on User Expansion to pin 2 (CAN_RX) on the CAN transceiver Header 1

  2. AM62x pin 10 (MCAN0_TX) on User Expansion to pin 1 (CAN_TX) on the CAN transceiver Header 1

  3. AM62x pin 22 (MCU_MCAN0_RX) on MCU Header to pin 2 (CAN_RX) on the CAN transceiver Header 1

  4. AM62x pin 16 (MCU_MCAN0_TX) on MCU Header to pin 1 (CAN_TX) on the CAN transceiver Header 1

  5. AM62x pin 11 (MCU_MCAN1_RX) on MCU Header to pin 2 (CAN_RX) on the CAN transceiver Header 1

  6. AM62x pin 10 (MCU_MCAN1_TX) on MCU Header to pin 1 (CAN_TX) on the CAN transceiver Header 1

The new CAN nodes can then be inserted to a working CAN setup or to test only on AM62x, the following can be done:

  1. 3x CAN transceiver pin 1 (CANL) on Header 2 together

  2. 3x CAN transceiver pin 2 (CANH) on Header 2 together

Below is an image of 3x MCAN on AM62x as described by the setup above:

../../../_images/mcan-test2.JPG

Test 3x MCAN on AM62x

Now CAN utilities software can be used to test, use CANDUMP command for one or two MCANs to display the received packets, and use the last MCAN to send CAN packets using the CANSEND or CANGEN commands. For more information on using CANUTILS go here: MCAN.


6.1.5.6. Enable Device Tree Overlay

Since AM62 SKs do not have on-board CAN transceivers, there are no transceiver nodes in their respective DTS files.

A device tree overlay named k3-am62x-sk-mcan.dtbo is supported in the Processor SDK 9.1 for the following devices:

  1. AM62x SK

  2. AM62SIP SK

  3. AM62x LP SK

  4. AM62Ax SK

An overlay can be used to dynamically overlay each DTB. If an AM62 .wic image was flashed to an SD card, the overlay should be found in the “root” partition in path: boot/dtb/ti. This overlay can be loaded by stopping bootup at U-boot prompt and executing the following commands:

For 8.6 and 9.1 SDK:

Hit any key to stop autoboot:  0
        =>
        => setenv name_overlays <name-of-overlay>.dtbo
        => boot

For 9.0 SDK:

Hit any key to stop autoboot:  0
        =>
        => setenv name_overlays ti/<name-of-overlay>.dtbo
        => boot