Getting started with an IVT-S and Arduino Uno CAN bus shield

First of all, set up your Arduino Uno and CAN bus shield.

Once the data is coming in over CAN, we can write a simple program to read the current value from the IVT-S

Here's the code:

// IVT-S meter using CAN-BUS Shield // electric_dart 2020

1. include <SPI.h>
2. include "mcp_can.h"

/*SAMD core*/

1. ifdef ARDUINO_SAMD_VARIANT_COMPLIANCE

   #define SERIAL SerialUSB

1. else

   #define SERIAL Serial

1. endif

// the cs pin of the version after v1.1 is default to D9 // v0.9b and v1.0 is default D10 const int SPI_CS_PIN = 10; const int CAN_INT_PIN = 2;

MCP_CAN CAN(SPI_CS_PIN); // Set CS pin

unsigned char flagRecv = 0; unsigned char len = 0; unsigned char buf[8]; char str[20];

void setup() {

   SERIAL.begin(115200);
   while (!SERIAL) {
       ; // wait for serial port to connect. Needed for native USB port only
   }
   while (CAN_OK != CAN.begin(CAN_1000KBPS)) {            // init can bus
       SERIAL.println("CAN BUS Shield init fail");
       SERIAL.println("Init CAN BUS Shield again");
       delay(100);
   }
   SERIAL.println("CAN BUS Shield init ok!");

   attachInterrupt(digitalPinToInterrupt(CAN_INT_PIN), MCP2515_ISR, FALLING); // start interrupt

   /*
       set receive mask
   */
   CAN.init_Mask(0, 0, 0x7ff);                         // there are 2 masks in mcp2515, you need to set both of them
   CAN.init_Mask(1, 0, 0x7ff);                         // 0x7ff is '11111111111' in binary, so we are checking 11 of the CAN message ID bits  

   /*
       set receive filter
   */
   CAN.init_Filt(0, 0, 0x521);                          // there are 6 filters in mcp2515
   CAN.init_Filt(1, 0, 0x521);                          // 0x521 is the CAN mssage ID for IVT-S Current value
   CAN.init_Filt(2, 0, 0x521);                          
   CAN.init_Filt(3, 0, 0x521);                          
   CAN.init_Filt(4, 0, 0x521);                          
   CAN.init_Filt(5, 0, 0x521);                          

}

void MCP2515_ISR() {

   flagRecv = 1;

}

void loop() {

   if (flagRecv) {
       // check if get data

       flagRecv = 0;                   // clear flag

       // iterate over all pending messages
       // If either the bus is saturated or the MCU is busy,
       // both RX buffers may be in use and reading a single
       // message does not clear the IRQ conditon.
       while (CAN_MSGAVAIL == CAN.checkReceive()) {
           // read data,  len: data length, buf: data buf
           CAN.readMsgBuf(&len, buf);
           unsigned long canId = CAN.getCanId();

           if (canId == 0x521) {
             SERIAL.print("Data received from IVT_Msg_Result_I");
             SERIAL.print("\t");
             // Convert individual big endian byte values to actual reading 
             long reading = (buf[2] << 24) | (buf[3] << 16) | (buf[4] << 8) | (buf[5]);
             SERIAL.print(reading);
           }

           SERIAL.println();
       }
   }

}