CAN Bus first attempt

As mentioned previously, I setup the Can-Bus v1.2 Shield and plugged it into my 2016 Mercedes c200 using the OBD-II cable.

I downloaded the Canbus library from HERE. Actually there was more code, but I was only interested in the Canbus.h/cpp library files for the Arduino. The sample they have includes SDCards, GPS, LCD screen and all I wanted was the simple stuff to start off with. Probably end up going the whole hog, but, small steps...

I wrote the following simple code:

#include <Canbus.h>

char buffer[512]; //Data will be temporarily stored to this buffer before being written to the output

void setup() {
Serial.begin(9600);
Serial.println("ECU Reader"); /* For debug use */
if(Canbus.init(CANSPEED_500)) /* Initialise MCP2515 CAN controller at the specified speed */
{
Serial.println("CAN Init ok");
} else
{
Serial.println("CAN'T init ok");
}
delay(1000);
}

void loop() {
if(Canbus.ecu_req(ENGINE_RPM,buffer) == 1) /* Request for engine RPM */
{
Serial.println("ENGINE RPM");
Serial.println(buffer);
}

if(Canbus.ecu_req(VEHICLE_SPEED,buffer) == 1) /* Request for vehicle KM */
{
Serial.println("VEHICLE SPEED");
Serial.println(buffer);
}

if(Canbus.ecu_req(ENGINE_COOLANT_TEMP,buffer) == 1) /* Cooland temperature */
{
Serial.println("ENGINE COOLANT TEMP");
Serial.println(buffer);
}

if(Canbus.ecu_req(THROTTLE,buffer) == 1) /* How much you pressed the pedal down */
{
Serial.println("THROTTLE");
Serial.println(buffer);
}
delay(100);
}

Plugged in the Arduino and then watched the Serial output:

---------------------------

ECU Reader

CAN Init ok

ENGINE RPM

0 rpm

ENGINE RPM

0 rpm

ENGINE RPM

0 rpm

ENGINE RPM

0 rpm

ENGINE RPM

0 rpm

ENGINE RPM

179 rpm

ENGINE RPM

1536 rpm

ENGINE RPM

1500 rpm

ENGINE RPM

1493 rpm

ENGINE RPM

1385 rpm

ENGINE RPM

1260 rpm

ENGINE RPM

1185 rpm

ENGINE RPM

1163 rpm

ENGINE RPM

1153 rpm

ENGINE RPM

1145 rpm

ENGINE RPM

1143 rpm

ENGINE RPM

1170 rpm

THROTTLE

15 %

ENGINE COOLANT TEMP

17 degC

ENGINE RPM

1119 rpm

ENGINE COOLANT TEMP

18 degC

ENGINE RPM

1084 rpm

ENGINE RPM

1107 rpm

ENGINE RPM

1023 rpm

ENGINE RPM

1001 rpm

ENGINE RPM

1001 rpm

ENGINE RPM

981 rpm

ENGINE RPM

994 rpm

ENGINE RPM

980 rpm

ENGINE RPM

982 rpm

ENGINE RPM

979 rpm

THROTTLE

14 %

ENGINE COOLANT TEMP

20 degC

ENGINE RPM

986 rpm

ENGINE RPM

986 rpm

ENGINE RPM

983 rpm

ENGINE RPM

976 rpm

ENGINE RPM

969 rpm

ENGINE RPM

982 rpm

THROTTLE

13 %

ENGINE RPM

971 rpm

ENGINE RPM

951 rpm

ENGINE COOLANT TEMP

22 degC

ENGINE RPM

948 rpm

THROTTLE

13 %

ENGINE RPM

961 rpm

ENGINE COOLANT TEMP

22 degC

ENGINE RPM

1039 rpm

ENGINE RPM

1038 rpm

ENGINE RPM

1008 rpm

ENGINE RPM

973 rpm

ENGINE RPM

956 rpm

ENGINE COOLANT TEMP

23 degC

ENGINE RPM

916 rpm

ENGINE RPM

914 rpm

ENGINE RPM

897 rpm

ENGINE RPM

894 rpm

ENGINE RPM

883 rpm

ENGINE RPM

881 rpm

ENGINE RPM

1844 rpm

ENGINE RPM

1423 rpm

ENGINE COOLANT TEMP

25 degC

ENGINE RPM

1024 rpm

ENGINE RPM

941 rpm

ENGINE RPM

883 rpm

ENGINE RPM

1096 rpm

ENGINE RPM

1311 rpm

VEHICLE SPEED

0 km

ENGINE RPM

1043 rpm

ENGINE RPM

928 rpm

ENGINE RPM

897 rpm

ENGINE RPM

863 rpm

ENGINE RPM

857 rpm

ENGINE COOLANT TEMP

27 degC

ENGINE COOLANT TEMP

27 degC

THROTTLE

12 %

ENGINE RPM

860 rpm

ENGINE RPM

856 rpm

ENGINE RPM

858 rpm

ENGINE RPM

860 rpm

THROTTLE

12 %

ENGINE RPM

851 rpm

ENGINE RPM

842 rpm

THROTTLE

12 %

ENGINE COOLANT TEMP

28 degC

ENGINE RPM

829 rpm

ENGINE RPM

826 rpm

ENGINE RPM

829 rpm

THROTTLE

12 %

ENGINE RPM

827 rpm

ENGINE RPM

827 rpm

ENGINE RPM

825 rpm

ENGINE RPM

831 rpm

ENGINE RPM

828 rpm

ENGINE RPM

812 rpm

ENGINE RPM

816 rpm

VEHICLE SPEED

0 km

ENGINE RPM

818 rpm

ENGINE RPM

814 rpm

ENGINE RPM

817 rpm

ENGINE RPM

821 rpm

ENGINE RPM

819 rpm

ENGINE RPM

818 rpm

THROTTLE

11 %

ENGINE RPM

808 rpm

ENGINE RPM

807 rpm

ENGINE COOLANT TEMP

30 degC

ENGINE RPM

810 rpm

---------------------------

Yaaay! It's alive. We can get proper, realistic data from the car.

The following C Header file shows the HEX values of the PID that we are currently listening for:

As per the list HERE, you can see how they tally up, ie. 0x0C = ENGINE_RPM.

The nice thing about this library is that the author has done some work for you already in relation to turning the data values received into a value that is meaningful:

For instance, the ENGINE_RPM is shown as:

That translates in the C code:



 case ENGINE_RPM:     //   ((A*256)+B)/4    [RPM]

 engine_data =  ((message.data[3]*256) + message.data[4])/4;

 sprintf(buffer,"%d rpm ",(int) engine_data);

Now, you can start to get creative and add more sensors to read and using the OBD-II PID guide, we can add the required formulas in code. As has been said, 1,000,000 times before, the car manufacturers do use these basic PID codes, but they also use custom ones and obviously their own formulas too.

We can change the Arduino code to just dump out everything is hears on the Can-Bus:

void loop()
{ 
tCAN message;

if (mcp2515_check_message()) 
 {
    if (mcp2515_get_message(&message)) 
 {
               Serial.print("ID: ");
               Serial.print(message.id,HEX);
               Serial.print(", ");
               Serial.print("Data: ");
               for(int i=0;i<message.header.length;i++)
                {
                  Serial.print(message.data[i],HEX);
                  Serial.print(" ");
                }
               Serial.println("");
             }}
}

One idea would be to have a trigger (button press?) and then perform a specific action in the car, such as open drivers window, then press the trigger again. Then analyse the data captured to work out what the codes were that were opening the window.

Then...get adventurous and call the sendMessage() command to the car CanBus to tell it to open the window.

Right, enough playing around with the Mercedes, I now need to test this on the 2001 MG F and see if I can get anything useful from that car!

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CAN Bus first attempt

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