Reading ECU data via CAN-BUS and MCP2515

Using Arduino Networking, Protocols, and Devices
1

I have been trying to build an Arduino dashboard for an F-SAE project that displays ECU data from the CAN-BUS, but can't find any good code to base it off of to get me started. My setup is an UNO, connected to an MCP2515 module:

These have an 8Mhz crystal, which I have read can change a number of parameters.

I've found a few "CAN-BUS read" examples from libraries I'm using, like this: MCP_CAN_lib/CAN_receive.ino at master · coryjfowler/MCP_CAN_lib · GitHub
which somewhat works, but lists off a bunch of PID's in the Serial Monitor, and I'm not sure how to narrow it down to specifics like engine RPM or temperature.

I'm worried about screwing something up, as I've tried testing some code on my personal vehicle (a 13' Chevy Volt), and the SparkFun ECU demo code from their library made my car give off a bunch of error messages, get 40+ fault codes, and the engine started on its own. The code in question, only change I made was to delete the parts about the GPS and LCD:

Would anyone have a working sample code, or can steer me in the right direction? I'm familiar with PID assignments, and if I can at least get something like RPM data working I could figure out the rest. Thank you for any help.

2

did you try something like this to send and received/decode your PIDs?
(code compiles with the library here: GitHub - coryjfowler/MCP_CAN_lib: MCP_CAN Library)

// Service 01 PIDs (more detail: https://en.wikipedia.org/wiki/OBD-II_PIDs)
#define PID_ENGINE_LOAD 0x04
#define PID_COOLANT_TEMP 0x05
#define PID_SHORT_TERM_FUEL_TRIM_1 0x06
#define PID_LONG_TERM_FUEL_TRIM_1 0x07
#define PID_SHORT_TERM_FUEL_TRIM_2 0x08
#define PID_LONG_TERM_FUEL_TRIM_2 0x09
#define PID_FUEL_PRESSURE 0x0A
#define PID_INTAKE_MAP 0x0B
#define PID_ENGINE_RPM  0x0C
#define PID_VEHICLE_SPEED 0x0D
#define PID_TIMING_ADVANCE 0x0E
#define PID_INTAKE_TEMP 0x0F
#define PID_MAF_FLOW 0x10
#define PID_THROTTLE 0x11
#define PID_AUX_INPUT 0x1E
#define PID_RUNTIME 0x1F
#define PID_DISTANCE_WITH_MIL 0x21
#define PID_COMMANDED_EGR 0x2C
#define PID_EGR_ERROR 0x2D
#define PID_COMMANDED_EVAPORATIVE_PURGE 0x2E
#define PID_FUEL_LEVEL 0x2F
#define PID_WARMS_UPS 0x30
#define PID_DISTANCE 0x31
#define PID_EVAP_SYS_VAPOR_PRESSURE 0x32
#define PID_BAROMETRIC 0x33
#define PID_CATALYST_TEMP_B1S1 0x3C
#define PID_CATALYST_TEMP_B2S1 0x3D
#define PID_CATALYST_TEMP_B1S2 0x3E
#define PID_CATALYST_TEMP_B2S2 0x3F
#define PID_CONTROL_MODULE_VOLTAGE 0x42
#define PID_ABSOLUTE_ENGINE_LOAD 0x43
#define PID_AIR_FUEL_EQUIV_RATIO 0x44
#define PID_RELATIVE_THROTTLE_POS 0x45
#define PID_AMBIENT_TEMP 0x46
#define PID_ABSOLUTE_THROTTLE_POS_B 0x47
#define PID_ABSOLUTE_THROTTLE_POS_C 0x48
#define PID_ACC_PEDAL_POS_D 0x49
#define PID_ACC_PEDAL_POS_E 0x4A
#define PID_ACC_PEDAL_POS_F 0x4B
#define PID_COMMANDED_THROTTLE_ACTUATOR 0x4C
#define PID_TIME_WITH_MIL 0x4D
#define PID_TIME_SINCE_CODES_CLEARED 0x4E
#define PID_ETHANOL_FUEL 0x52
#define PID_FUEL_RAIL_PRESSURE 0x59
#define PID_HYBRID_BATTERY_PERCENTAGE 0x5B
#define PID_ENGINE_OIL_TEMP 0x5C
#define PID_FUEL_INJECTION_TIMING 0x5D
#define PID_ENGINE_FUEL_RATE 0x5E
#define PID_ENGINE_TORQUE_DEMANDED 0x61
#define PID_ENGINE_TORQUE_PERCENTAGE 0x62
#define PID_ENGINE_REF_TORQUE 0x63
//----------------------------------------------

#define CAN_ID_PID 0x7DF //OBD-II CAN frame ID

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

#define CAN0_INT 2                              // Set INT to pin 2  <--------- CHANGE if using different pin number
MCP_CAN CAN0(10);                               // Set CS to pin 10 <--------- CHANGE if using different pin number

long unsigned int rxId;
unsigned char len = 0;
unsigned char rxBuf[8];
char msgString[128];                        // Array to store serial string

void sendPID(unsigned char __pid)
{
  unsigned char tmp[8] = {0x02, 0x01, __pid, 0, 0, 0, 0, 0};

  byte sndStat = CAN0.sendMsgBuf(CAN_ID_PID, 0, 8, tmp);

  if (sndStat == CAN_OK) {
    Serial.print("PID sent: 0x");
    Serial.println(__pid, HEX);
  }
  else {
    Serial.println("Error Sending Message...");
  }
}

void receivePID(unsigned char __pid)
{
    if (!digitalRead(CAN0_INT)) {                      // If CAN0_INT pin is low, read receive buffer
    CAN0.readMsgBuf(&rxId, &len, rxBuf);      // Read data: len = data length, buf = data byte(s)

    sprintf(msgString, "Standard ID: 0x%.3lX, DLC: %1d, Data: ", rxId, len);
    Serial.print(msgString);

    for (byte i = 0; i < len; i++) {
      sprintf(msgString, " 0x%.2X", rxBuf[i]);
      Serial.print(msgString);
    }
    Serial.println("");


    switch (__pid) {
      case PID_COOLANT_TEMP:
        if(rxBuf[2] == PID_COOLANT_TEMP){
          uint8_t temp;
          temp = rxBuf[3] - 40;
          Serial.print("Engine Coolant Temp (degC): ");
          Serial.println(temp, DEC);
        }
      break;

      case PID_ENGINE_RPM:
        if(rxBuf[2] == PID_ENGINE_RPM){
          uint16_t rpm;
          rpm = ((256 * rxBuf[3]) + rxBuf[4]) / 4;
          Serial.print("Engine Speed (rpm): ");
          Serial.println(rpm, DEC);
        }
      break;
    }
  }
}

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

  // Initialize MCP2515 running at 16MHz with a baudrate of 500kb/s and the masks and filters disabled.
  if (CAN0.begin(MCP_STDEXT, CAN_500KBPS, MCP_16MHZ) == CAN_OK) { //< -------- - CHANGE if using different board
    Serial.println("MCP2515 Initialized Successfully!");
  }
  else {
    Serial.println("Error Initializing MCP2515...");
    while (1);
  }

  //initialise mask and filter to allow only receipt of 0x7xx CAN IDs
  CAN0.init_Mask(0, 0, 0x07000000);              // Init first mask...
  CAN0.init_Mask(1, 0, 0x07000000);              // Init second mask...

  
  for (uint8_t i = 0; i < 6; ++i) {
    CAN0.init_Filt(i, 0, 0x07000000);           //Init filters
  }
  
  CAN0.setMode(MCP_NORMAL);                     // Set operation mode to normal so the MCP2515 sends acks to received data.

  pinMode(CAN0_INT, INPUT);                    // Configuring pin for /INT input

  Serial.println("Sending and Receiving OBD-II_PIDs Example...");
}

void loop()
{
  //request coolant temp
  sendPID(PID_COOLANT_TEMP);

  delay(40); //to allow time for ECU to reply

  receivePID(PID_COOLANT_TEMP);

  //request engine speed
  sendPID (PID_ENGINE_RPM);

  delay(40); //to allow time for ECU to reply

  receivePID(PID_ENGINE_RPM);

  //abitrary loop delay
  delay(40);

}
3

Thanks for the code, that has gotten a better response from my vehicle. The coolant numbers don't seem right though as they vary quite a bit in the Serial Monitor, and the engine isn't even running yet. (See screen shot).
The engine RPM doesn't return either, even with the engine running. Granted, my car is a hybrid, so it may not have one, as I don't see it's PID in the data output.

Thank you so much again!

Screenshot 2019-06-20 at 4.37.19 PM.png
Screenshot 2019-06-20 at 4.37.19 PM.png1366×768 109 KB

4

Allen42B:
Thanks for the code, that has gotten a better response from my vehicle. The coolant numbers don't seem right though as they vary quite a bit in the Serial Monitor, and the engine isn't even running yet. (See screen shot).
The engine RPM doesn't return either, even with the engine running. Granted, my car is a hybrid, so it may not have one, as I don't see it's PID in the data output.

Thank you so much again!

something's not right there.... can you confirm you made the recommended changes tothe code to match your setup?

you are reading multiple CAN IDs in that screenshoot when I expected only 0x7xx CAN ids since in the code the CAN filter is initialised. so the code is bascially decoding the wrong messages hence the wierd results.anyway...

if you check the wiki link in the code comments, under "CAN (11-bit) bus format" it mentioned a range of reply CAN IDs

if you can confirm that reply ID you are getting from that range you can adjust the code to only read and decode that particular CAN ID which should then fix the issue

5

I see what I did wrong. At Line 122, I had made sure the crystal and Can-Bus speed was right, but didn't change the filtering. I switched it to "MCP_STDEXT" which filtered down the results. I ran the engine and confirmed real time data changes that seemed accurate. "MCP_STD" showed no results initially, so I'm assuming it is filtering at "MCP_EXT" now. My car isn't the final destination for this product, so I'll have to keep track of which to use in the future. One last question, if I wish to read additional parameters from the ECU, is there anything else I need to change, other than adding the send and receive commands into the loop?

Thank you again so much, this is exactly what I needed to get started.

6

Allen42B:
is there anything else I need to change, other than adding the send and receive commands into the loop?

you should not have to change anything in the 'send' routine but you will need to update the 'receive' routine to include the new parameter you would be reading/decoding.

Good luck! :slight_smile:

7

Hi all. I tried sherzaad code too but i not received any message from ECU.
it is a me7.5
Anybody can help with more advices?
Many thanks in advance

8

is there a tutorial?
i am interested to learn it
thanks