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PiCAN2 Duo CAN Bus Board for Raspberry Pi - Functionality Test

Posted by Wilfried Voss on

PiCAN2 Duo CAN-Bus Board for Raspberry Pi - Test Configuration

The  PiCAN2 DUO board provides two independent CAN Bus interfaces for the Raspberry Pi. It uses the Microchip MCP2515 CAN Bus controller with MCP2551 CAN Bus transceiver. Connections are made via a 4-way screw terminal. This board is also available with a 5VDC/1A SMPS (switch mode power supply) that can power both the Pi and the CAN Bus HAT. There is an easy-to-install SocketCAN driver, and programming can be accomplished in C or Python.

In our experience, many users are quick with connecting the PiCAN CAN Bus board to their CAN hardware, and they are frustrated when the communication doesn't work. In the vast majority of these cases, the problem is not with the PiCAN board but with the external connection. For that reason, we recommend testing the PiCAN board without external hardware, which helps to methodically pinpoint the problem.

The following describes a fairly simple method of "dry-testing" the board, i.e. without the need of connecting to a real-world CAN Bus network. The dual CAN Bus interface makes testing easy, because you already have two CAN Bus nodes available, which is sufficient to establish a network.

Note: It may sound obvious, but many users forget that you need a minimum of two nodes to establish a network, otherwise the CAN Bus controller will return error messages.

For the following test, we assume the following:

  1. You have setup the device (config.txt file) as described in the user manual.
  2. You have installed the demo programs, specifically candump and cansend as described in the user manual.
  3. You have both termination resistors activated by closing the corresponding jumpers.
  4. You have connected both CAN Bus ports, i.e. you have connected CAN_L to CAN_L and CAN_H to CAN_H.
  5. You have NOT initialized or accessed the board by means of an application software running on the Raspberry Pi.

In our case, we installed the demo programs in the /Documents/test-can_pi2 folder. Open a terminal window, switch to the folder where you have installed the programs, and initialize both CAN Bus ports:

sudo /sbin/ip link set can0 up type can bitrate 500000
sudo /sbin/ip link set can0 up type can bitrate 500000

We are using a CAN Bus baud rate of 500000 only as an example, but you can use any other bitrate as long as they match for both ports. 

The initialization also represents a first test of the board, i.e. if the port is defective there will be an error message, otherwise there will be no response. Assuming that there is no error message, type the following command:

./candump can0 -n1

This line will print out the next CAN Bus data frame as soon as it was received. Now open a new terminal window, switch to the folder where you installed the sample programs, and here enter the following line:

./cansend can1 7DF#8877665544332211

This procedure sends a (randomly designed) CAN Bus data frame from port 1 to port 0. The result, i.e. the received data frame will be displayed in the other terminal window.

In our example, we repeated the procedure by sending date from port 0 to port 1.

If, however, you still have problems getting the board to communicate with your external CAN node, have a look at Troubleshooting your PiCAN2 CAN Interface Board for Raspberry PI.


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