Arduino UNO R4 WiFi CAN Bus

In this tutorial you will learn how to use the CAN controller on the Arduino UNO R4 WiFi board. The CAN controller is embedded in the UNO R4 WiFi's microcontroller (RA4M1). CAN is a serial protocol that is mainly used in the automotive industry.

Please note that CAN controller requires an external transceiver to function. Instructions and hardware examples are provided in this tutorial.

Goals

The goals of this tutorial are:

• Get an overview of the built-in CAN library
• Learn how to connect a board to a CAN transceiver module
• Send a CAN message between two Arduinos

Hardware & Software Needed

• Arduino IDE (online or offline)
• Arduino R4 WiFi
• Arduino Renesas Core
• CAN transceiver module *
• Jumper wires

* In this tutorial, we are using a SN65HVD230 breakout module.

Controller Area Network (CAN)

The CAN bus uses two wires: CAN high and CAN low. On the UNO R4 WiFi, these pins are:

• D13/CANRX0 (receive)
• D10/CANTX0 (transmit)

To communicate with other CAN devices however, you need a transceiver module. In this tutorial, we will be using a SN65HVD230 breakout. To connect this, you can follow the circuit diagram available in the section below.

For this tutorial, we will use a simple example that sends a CAN message between two UNO R4 WiFi devices. If you wish, you can also connect an existing CAN device to the UNO R4 WiFi.

Circuit

To connect the CAN transceiver, follow the table and circuit diagram below:

Then, between the CAN transceivers, connect the following:

Code Examples

The following code examples need to be uploaded to each of the UNO R4 WiFi boards, one will send a message, one will receive it. These examples are available in the Renesas core, and using the Arduino IDE, you can access them by navigating to File > Examples > Arduino_CAN > CANWrite/CANRead

The library used is built into the core, so no need to install the library if you have the core installed.

To initialize the library, use

CAN.begin(CanBitRate::BR_250k)

• BR_125k (125000)
• BR_250k (250000)
• BR_500k (500000)
• BR_1000k (1000000)

CAN Write

To send a CAN message, you can create a

CanMsg

CAN_ID

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1uint8_t const msg_data[] = {0xCA,0xFE,0,0,0,0,0,0};
2memcpy((void *)(msg_data + 4), &msg_cnt, sizeof(msg_cnt));
3CanMsg msg(CAN_ID, sizeof(msg_data), msg_data);

After you have crafted a CAN message, we can send it off, by using the

CAN.write()

void loop()

Copy
1

CAN Read

To read an incoming CAN message, first use

CAN.available()

CAN.read()

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1

Summary

This tutorial shows how to use the CAN bus available on the UNO R4 WiFi, and how to send and receive data using the Arduino_CAN library.

Read more about this board in the Arduino UNO R4 WiFi documentation.