I2C CAN Bus Module

Introduction


We launched the Serial CAN Bus Module years ago, which is very practial and easy to use. Now we have slightly modified the Serial CAN Bus Module, wrote a special firmware, and launched this I2C CAN Bus Module.

The I2C CAN Bus Module uses I2C for communication. The board is small and flexible, which make it can be quickly used in any system with an I2C interface.

The I2C CAN Bus Module is based on the high-performance MCP2515 CAN Bus controller and MCP2551 CAN Bus transceiver, provides a CAN Bus communication rate of up to 1Mb/s.

In addition, there is an Atmega168PA microcontroller on the board, you can also program it through a USB to Serial board, modify the firmware or write your application directly.

Note

The default masks and filters is for standard can frame, if you need to receive a ext can frame, please set the mask and filt first.

CAN BUS PRODUCTS LIST OF LONGAN-LABS

We have made a lot of can bus products, you can get more information through the following list, so as to choose a product suitable for you.

PRODUCT NAME LINK PRICE MCU CHIP PROTOCOL
Serial CAN Bus Module LINK $14.9 ATMEGA168PA MCP2515 CAN2.0
I2C CAN Bus Module LINK $14.9 ATMEGA168PA MCP2515 CAN2.0
OBD-II CAN Bus Dev Kit LINK $17.9 ATMEGA168PA MCP2515 CAN2.0
OBD-II CAN Bus GPS Dev Kit LINK $29.9 ATMEGA32U4 MCP2515 CAN2.0
OBD-II CAN Bus Basic Dev Kit LINK $19.9 ATMEGA32U4 MCP2515 CAN2.0
CAN-FD Shield LINK $8.9 NO MCU MCP2517FD CAN-FD
CAN Bus Shield LINK $5.9 NO MCU MCP2515 CAN2.0
CANBed LINK $19.9 ATMEGA32U4 MCP2515 CAN2.0
CANBed-FD LINK $19.9 ATMEGA32U4 MCP2517FD CAN-FD
CANBed M0 LINK $19.9 ATSAMD21 MCP2515 CAN2.0
CANBed M4 LINK $24.9 ATSAME51 - CAN-FD

Partlist


Features


  • I2C to CAN Bus Conversion
  • Default I2C Address 0x25
  • Max I2C Speed: 400k
  • Work with Arduino/BeagleBone board/Pi or any MCU that integrated with I2C.
  • Up to 1Mb/s CAN Bus baud rate (default 500k)
  • TX and RX led indicator for CAN Bus
  • 4pin HY connector
  • 3.3 / 5V working voltage
  • Easy-to-use Arduino library
  • Small size: 20x40 mm

Hardware Overview


  1. 4 pin 2.0mm Connector (Same as Grove connector from Seeedstudio)
  2. Power and status led indicator
    • Blink all the time: CAN Bus init fail, Maybe the board was damaged
    • When receive data from I2C, blink one time
  3. Send and Recv led indicator
  4. 3.5mm terminal to connect to CAN Bus (CAN_H & CAN_L)
  5. 120Ω registor.

Note

The picture shows the Serial CAN Bus Module, but it is also applicable to the I2C CAN Bus Module

120 Terminal resistor

If you need the 120Ω terminal resistor, you need a soldering iron, as shown below:

Note

The picture shows the Serial CAN Bus Module, but it is also applicable to the I2C CAN Bus Module

I2C Register

Address Name Length Type Default Value Description
0x01 ADDR 1 Byte W 0x25 I2C Slaver Address
0x02 DNUM 1 Byte R 0 Counter of CAN Frames
0x03 BAUD 1 Byte W/R 16(500kb/s) CAN Baud Rate
0X30 SEND 1 Byte W - Send a frame
0x40 RECV 1 Byte R - Receive a frame
0x60 MASK0 5 Byte W/R 0 Mask 0
0x65 MASK1 5 Byte W/R 0 Mask 1
0x70 FILT0 5 Byte W/R 0 Filter 0
0x80 FILT1 5 Byte W/R 0 Filter 1
0x90 FILT2 5 Byte W/R 0 Filter 2
0xA0 FILT3 5 Byte W/R 0 Filter 3
0xB0 FILT4 5 Byte W/R 0 Filter 4
0xC0 FILT5 5 Byte W/R 0 Filter 5
0X30 SEND 16 Byte W - Send a frame
0x40 RECV 16 Byte R - Receive a frame

ADDR (0x01)

Set the I2C slaver address, default 0x25.

DNUM (0x02)

The I2C CAN Bus Module can store up to 16 CAN Frames. The number of CAN Frames currently stored in the device can be read this register. If the number of CAN frames stored in the device exceeds 16, the new CAN frame will overwrite the ones that were not read in time.

BAUD (0x01)

Set the baud rate of CAN Bus, which can be set to the following values.

value 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18
rate(kb/s) 5 10 20 25 31.2 33 40 50 80 83.3 95 100 125 200 250 500 666 1000

SEND (0x30), RECV (0x40)

Send/receive a CAN Frame, the length is 16 bytes, defined as follows:

Byte 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Define ID3 ID2 ID1 ID0 EXT RTR DLen D7 D6 D5 D4 D3 D2 D1 D0 CheckSum
  • ID3~ID0: CAN ID, 11/29 bit
  • EXT:
    • 1: Extended CAN Frame
    • 0: Standard CAN Frame
  • RTR:
    • 1: Remote CAN Frame
    • 0: Standard CAN Frame
  • Dlen: Length of a CAN Frame
  • D7~D0: Data of a CAN Frame
  • CheckSum: Check sum, get it as below,
unsigned char makeCheckSum(unsigned char *dta, int len)
{
    unsigned long sum = 0;
    for(int i=0; i<len; i++)sum += dta[i];

    if(sum > 0xff)
    {
        sum = ~sum;
        sum += 1;
    }

    sum  = sum & 0xff;
    return sum;
}

MASKn

Set Maskers, the length is 5 bytes, defined as follows:

Byte 4 3 2 1 0
Define EXT D3 D2 D1 D0
  • EXT:
    • 1: Extended CAN Frame
    • 0: Standard CAN Frame
  • D3~D0: Value for masker, 11/29

FILTn

Set Filters, the length is 5 bytes, defined as follows:

Byte 4 3 2 1 0
Define EXT D3 D2 D1 D0
  • EXT:
    • 1: Extended CAN Frame
    • 0: Standard CAN Frame
  • D3~D0: Value for filter, 11/29

Work with Arduino


120Ω Terminal Resistor

As there're only 2 serial can bus device, it need the 120Ω resistor, there's a P1 on the back side, please solder P1 to get the 120Ω resistor, as shown below,

Note

The picture shows the Serial CAN Bus Module, but it is also applicable to the I2C CAN Bus Module

Hardware Connection

There are 4 pins on the board, they are:

Pin Name Function Color
SCL SCL of I2C Yellow
SDA SDA of I2C White
VCC 3.3 or 5V Red
GND Ground Black

If you got a Base Shield from Seeedstudio, the connection is easy, like below,

If there's no Base Shield for you, you need some dupont cable, and connect SCL/SDA to the IO of your Arduino, here we connect SCL/SDA to A5/A4:

Software

We provide an Arduino Library for the board.

Please download it at Github

There're many examples for the library, which is consist of,

  • send - How to send a frame to CAN Bus
  • recv - How to recv a frame from CAN Bus
  • debug - debug mode, you can send a cmd to the module
  • set_can_baudrate - set can bus baudrate
  • set_mask_filt - set mask and filt of the module

Test the board

Here we make an example to show you how the board work with CAN Bus.

The connection like below, here we use Longan Core 01 + I2C CAN bus module as a receiver, and a CANBed V1 as CAN Bus sender.

Upload the recv example to Longan Core 01

/*  receive a frame from can bus
    support@longan-labs.cc

    CAN Baudrate,

    #define CAN_5KBPS           1
    #define CAN_10KBPS          2
    #define CAN_20KBPS          3
    #define CAN_25KBPS          4 
    #define CAN_31K25BPS        5
    #define CAN_33KBPS          6
    #define CAN_40KBPS          7
    #define CAN_50KBPS          8
    #define CAN_80KBPS          9
    #define CAN_83K3BPS         10
    #define CAN_95KBPS          11
    #define CAN_100KBPS         12
    #define CAN_125KBPS         13
    #define CAN_200KBPS         14
    #define CAN_250KBPS         15
    #define CAN_500KBPS         16
    #define CAN_666KBPS         17
    #define CAN_1000KBPS        18
*/

#include <Wire.h>

#include "Longan_I2C_CAN_Arduino.h"


I2C_CAN CAN(0x25);                                    // Set I2C Address

void setup()
{
    Serial.begin(115200);
    //while(!Serial);

    Serial.println("begin to init can");

    while (CAN_OK != CAN.begin(CAN_500KBPS))    // init can bus : baudrate = 500k
    {
        Serial.println("CAN BUS FAIL!");
        delay(100);
    }
    Serial.println("CAN BUS OK!");
    pinMode(13, OUTPUT);
}


void loop()
{
    unsigned char len = 0;
    unsigned char buf[8];

    if(CAN_MSGAVAIL == CAN.checkReceive())            // check if data coming
    {
        CAN.readMsgBuf(&len, buf);    // read data,  len: data length, buf: data buf

        if(len)
        {
            unsigned long canId = CAN.getCanId();

            Serial.print("Get ID: ");
            Serial.println(canId, HEX);

            for(int i = 0; i<len; i++)    // print the data
            {
                Serial.print(buf[i], HEX);
                Serial.print("\t");
            }
            Serial.println();
        }
    }

    delay(10);
    blink();
}

void blink()
{
    static unsigned long timer_s = millis();
    if(millis()-timer_s < 100)return;
    timer_s = millis();
    digitalWrite(13, 1-digitalRead(13));
}
// END FILE

Then, upload send example to CANBed.

Open Serial monitor of Longan Core 01, you will get the can frame from CAN Bus.

Working Standalone


For V1.2 and after, you can program the on-board MCU (Atmega168PA) with Arduino IDE.

First, you need a USB to Serial board, something like the Programmer Card

Here we will take Programmer Card as an example:

Note

The picture shows the Serial CAN Bus Module, but it is also applicable to the I2C CAN Bus Module

Then, we need to setup your Arduino IDE.

Start the Arduino IDE.

Copy and paste the link below into the Additional Boards Manager URLs option in the Arduino IDE preferences (File > Preferences).

https://raw.githubusercontent.com/Longan-Labs/Longan-Board/master/package_longan_boards_index.json

The Longan AVR boards supplied package includes supports for Longan Card, Carduino 328, Carduino 32U4.

Once done, click OK button to save the new preference settings.

Now open the Boards Manager by navigating to the Tools -> Board menu.

Select All from the Type drop-down menu. Then type longan in the top search bar. While typing, you will see the Longan AVR package.

Click on the Longan AVR by Longan Labs and then click on Install button.

Once installed, close the Boards Manager window.

Then you can find Serial CAN Bus Module in the board list.

FAQ

The RX and TX leds light up instead of blinking

  • Please check the baudrate of CAN Bus
  • If the serial can bus module is in the end, the 120Ω terminal resistor is needed, please soder P1 on the back side of PCBA

How to find the tech support

Please feel free to contact joney.sui@longan-labs.cc if you need more help.

Schematic Online Viewer

Reference