ISO-tp frames

can_bus_main.go

func main() {
	fm := getMesh()

	// Initialize the mesh: set diagnostic frames to USB port, so the laptop will send them
	laptopInstance.SendDataToUSB(
		diagnostics.FrameGetEngineDTCs,
		diagnostics.FrameGetSpeed,
		diagnostics.FrameGetRPM,
		diagnostics.FrameGetCoolantTemperature,
		diagnostics.FrameGetCalibrationID,
		diagnostics.FrameGetVIN,
		diagnostics.FrameGetTransmissionFluidTemperature,
	)

	runResult, err := fm.Run()
	if err != nil {
		fmt.Println("The mesh finished with error: ", err)
		os.Exit(1)
	}

	fmt.Printf("Mesh stopped after %d cycles and %s", runResult.Cycles.Len(), runResult.Duration)
}

iso_tp_frame.go

// FrameGetRPM is an ISO-TP Single Frame encoded inside one CAN frame.
// It requests the current Engine RPM via OBD-II (Mode 01, PID 0x0C).
FrameGetRPM = &codec.Frame{
	// 0x7DF is the functional OBD-II request ID.
	// "Functional" means all ECUs that support this service may respond.
	Id:  0x7DF,

	// DLC = 8 because classic CAN always sends 8 data bytes.
	// Even if the payload is shorter, the frame must be padded.
	DLC: 8,

	Data: [8]byte{
		// ISO-TP Protocol Control Information (PCI)
		// High nibble: frame type (0 = Single Frame)
		// Low nibble: payload length in bytes
		// 0x02 means: Single Frame, 2 bytes of actual data follow
		0x02,

		// OBD-II Service ID (Mode)
		// 0x01 = "Show Current Data"
		0x01,

		// OBD-II Parameter ID (PID)
		// 0x0C = Engine RPM
		0x0C,

		// Padding bytes.
		// ISO-TP requires unused bytes in a CAN frame to be padded.
		// They have no meaning but must be present to fill all 8 bytes.
		0x00, 0x00, 0x00, 0x00, 0x00,
	},
}