Will simulate CAN-BUS messages for a ELM327 OBD sensor to read.

CAN-BUS Simulator V2

#include <SPI.h>
#include <mcp_can_dfs.h>
#include "mcp_can.h"

#define INT8U unsigned char
#define INT32U unsigned char
#define CAN_500KBPS  16
#define CAN_ID_PID          0x7DF

// 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 = 9;

MCP_CAN CAN(SPI_CS_PIN);                                      // Set CS to pin 10

unsigned char PID_INPUT;
unsigned char getPid    = 0;
unsigned char len = 0;
unsigned char buf[8];
char str[20];
String BuildMessage="";
int MSGIdentifier=0;

INT32U canId = 0x000;


void sendPid(unsigned char __pid)
{
    unsigned char tmp[8] = {0x02, 0x01, __pid, 0, 0, 0, 0, 0};
    Serial.print("SEND PID: 0x");
    Serial.println(__pid, HEX);
    CAN.sendMsgBuf(CAN_ID_PID, 0, 8, tmp);
}


void setup() {
  Serial.begin(115200);

START_INIT:

    if(CAN_OK == CAN.begin(CAN_500KBPS))                   // init can bus : baudrate = 500k
    {
        Serial.println("CAN BUS Shield init ok!");
    }
    else
    {
        Serial.println("CAN BUS Shield init fail");
        Serial.println("Init CAN BUS Shield again");
        delay(100);
        goto START_INIT;
    }
}

void loop()
{
    unsigned char rndCoolantTemp=random(1,200);
    unsigned char rndRPM=random(1,55);
    unsigned char rndSpeed=random(0,255);
    unsigned char rndIAT=random(0,255);
    unsigned char rndMAF=random(0,255);
    unsigned char rndAmbientAirTemp=random(0,200);
    unsigned char rndCAT1Temp=random(1,55);
    
    //GENERAL ROUTINE
    unsigned char SupportedPID[8] =       {255, 255, 255, 255, 255, 255, 255, 255};
    unsigned char MilCleared[7] =         {4, 65, 63, 34, 224, 185, 147}; 
    
    //SENSORS
    unsigned char CoolantTemp[7] =        {4, 65, 5, rndCoolantTemp, 0, 185, 147};  
    unsigned char rpm[7] =                {4, 65, 12, rndRPM, 224, 185, 147};
    unsigned char vspeed[7] =             {4, 65, 13, rndSpeed, 224, 185, 147};
    unsigned char IATSensor[7] =          {4, 65, 15, rndIAT, 0, 185, 147};
    unsigned char MAFSensor[7] =          {4, 65, 16, rndMAF, 0, 185, 147};
    unsigned char AmbientAirTemp[7] =     {4, 65, 70, rndAmbientAirTemp, 0, 185, 147};
    unsigned char CAT1Temp[7] =           {4, 65, 60, rndCAT1Temp, 224, 185, 147};
    unsigned char CAT2Temp[7] =           {4, 65, 61, rndCAT1Temp, 224, 185, 147};
    unsigned char CAT3Temp[7] =           {4, 65, 62, rndCAT1Temp, 224, 185, 147};
    unsigned char CAT4Temp[7] =           {4, 65, 63, rndCAT1Temp, 224, 185, 147};

    Serial.println(rndCoolantTemp);
    if(CAN_MSGAVAIL == CAN.checkReceive())  
    {
      Serial.println("Message Received \n");

      CAN.readMsgBuf(&len, buf); 
        canId = CAN.getCanId();
        Serial.print("<");Serial.print(canId);Serial.print(",");

        for(int i = 0; i<len; i++)
        {  
          BuildMessage = BuildMessage + buf[i] + ",";
        }
        Serial.println(BuildMessage);
        
        //Check wich message was received.
        if(BuildMessage=="2,1,0,0,0,0,0,0,") {CAN.sendMsgBuf(0x7E8, 0, 8, SupportedPID);}
        if(BuildMessage=="2,1,1,0,0,0,0,0,") {CAN.sendMsgBuf(0x7E8, 0, 7, MilCleared);}
        
        //SEND SENSOR STATUSES
        if(BuildMessage=="2,1,5,0,0,0,0,0,") {CAN.sendMsgBuf(0x7E8, 0, 7, CoolantTemp);}
        if(BuildMessage=="2,1,12,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, rpm);}
        if(BuildMessage=="2,1,13,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, vspeed);}
        if(BuildMessage=="2,1,15,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, IATSensor);}
        if(BuildMessage=="2,1,16,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, MAFSensor);}
        if(BuildMessage=="2,1,70,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, AmbientAirTemp);}
        if(BuildMessage=="2,1,60,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, CAT1Temp);}
        if(BuildMessage=="2,1,61,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, CAT2Temp);}
        if(BuildMessage=="2,1,62,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, CAT3Temp);}
        if(BuildMessage=="2,1,63,0,0,0,0,0,"){CAN.sendMsgBuf(0x7E8, 0, 7, CAT4Temp);}
        BuildMessage="";
    }
}



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

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

        Serial.println("\r\n------------------------------------------------------------------");
        Serial.print("Get Data From id: 0x");
        Serial.println(CAN.getCanId(), HEX);
        for(int i = 0; i<len; i++)    // print the data
        {
            Serial.print("0x");
            Serial.print(buf[i], HEX);
            Serial.print("\t");
        }
        Serial.println();
    }
}

void taskDbg()
{
    while(Serial.available())
    {
        char c = Serial.read();
        
        if(c>='0' && c<='9')
        {
            PID_INPUT *= 0x10;
            PID_INPUT += c-'0';
            
        }
        else if(c>='A' && c<='F')
        {
            PID_INPUT *= 0x10;
            PID_INPUT += 10+c-'A';
        }
        else if(c>='a' && c<='f')
        {
            PID_INPUT *= 0x10;
            PID_INPUT += 10+c-'a';
        }
        else if(c == '\n')      // END
        {
            getPid = 1;
        }
    }
}