Can-bus emulation for cruise control - Revision history

Arte: /* Emulating the cruise control switch */

2026-03-08T08:02:38Z

Emulating the cruise control switch

← Older revision		Revision as of 08:02, 8 March 2026
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	\|Message counter\|\|3\|\|4\|\|4\|\|0..15 (Phys = Hex)\|\|Rolling counter		\|Message counter\|\|3\|\|4\|\|4\|\|0..15 (Phys = Hex)\|\|Rolling counter
	\|-		\|-
	\|Not used\|\|4\|\|0\|\|8\|\|—\|\|Byte 4 unused		\|Not used\|\|4\|\|0\|\|8\|\|—\|\|Byte 4 unused for this purpose
	\|}		\|}

Line 232:		Line 232:
	\|MSR torque intervention\|\|7\|\|0\|\|8\|\|0 – 99.06 %\|\|		\|MSR torque intervention\|\|7\|\|0\|\|8\|\|0 – 99.06 %\|\|
	\|-		\|-
	\|Message counter\|\|8\|\|0\|\|4\|\|0 – 15\|\|		\|Message counter\|\|8\|\|0\|\|4\|\|0 – 15\|\|Rolling counter
	\|-		\|-
	\|ASR controller present\|\|8\|\|4\|\|1\|\|0 = ABS; 1 = ASR\|\|		\|ASR controller present\|\|8\|\|4\|\|1\|\|0 = ABS; 1 = ASR\|\|

Arte: /* Emulating the ABS module (Vehicle speed) */

2026-03-08T08:01:29Z

Emulating the ABS module (Vehicle speed)

← Older revision		Revision as of 08:01, 8 March 2026
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	\|Rear right direction\|\|7\|\|0\|\|1\|\|0 = forward; 1 = reverse\|\|		\|Rear right direction\|\|7\|\|0\|\|1\|\|0 = forward; 1 = reverse\|\|
	\|-		\|-
	\|Rear right wheel speed\|\|7 & 8\|\|0\|\|15\|\|0..326 km/h\|\|		\|Rear right wheel speed\|\|7 & 8\|\|1\|\|15\|\|0..326 km/h\|\|
	\|}		\|}

Arte: /* Emulating the ABS module (Vehicle speed) */

2026-03-08T07:58:48Z

Emulating the ABS module (Vehicle speed)

@@ Line 181: / Line 181: @@
 Regarding the ABS, more CAN message will need to be emulated:
 {{Note|note-reminder|This section is under development. Feel free to add content.}}
-== Monitoring the values received by the ECU ==
+Speed signal constants for the combined value of '''Byte 3 and Byte 4'''
 You can use any suitable scanner, such as VCDS, and monitor the channel '''066''' in the measurement values.
 This channel lists:
-* Vehicle speed
+*Vehicle speed
-* Clutch/Brake switch values
+*Clutch/Brake switch values
-* Cruise control switch values
+*Cruise control switch values
-* Cruise control status
+*Cruise control status

Arte: /* Code example */

2026-02-25T06:04:36Z

Code example

← Older revision		Revision as of 06:04, 25 February 2026
Line 75:		Line 75:
	This is a very rough sketch to show a possible implementation. This example would be for an Arduino controller using a MCP2515 shield (hat).		This is a very rough sketch to show a possible implementation. This example would be for an Arduino controller using a MCP2515 shield (hat).

	<syntaxhighlight lang="c" line="">		<syntaxhighlight lang="c" line="1">
	// demo: Cruise control switch, analog to can-bus message for VW PQ35		// demo: Cruise control switch, analog to can-bus message for VW PQ35
	// Very rough sketch, but should work. Feel free to improve		// Very rough sketch, but should work. Feel free to improve
Line 138:		Line 138:
	int stateSet = digitalRead(buttonSet);		int stateSet = digitalRead(buttonSet);

	// You can more inputs and adjust the logic according the the can-bus chart		// You can add more inputs and adjust the logic according the the can-bus chart
	if (stateMain == LOW) {		if (stateMain == LOW) {
	switchState \|= (1 << 0); // Set bit 0		switchState \|= (1 << 0); // Set bit 0

Arte at 17:10, 20 February 2026

2026-02-20T17:10:00Z

Show changes

Arte: Initial page

2026-02-20T16:44:16Z

Initial page

New page

==Introduction==
This is intended as a reference for those who would like to emulate the can-bus messages for the cruise control.

'''Application''': Any swapped vehicles that do not have can-bus support. It would cover both the Bosch ME7.1.1 and a ME17.5/ME17.5.6

==Hardware required==
You can use any microcontroller that have CAN-bus capability, such as an Arduino or ESP32. You could also use the SpeedPulser Pro that already has a GPS and CAN-bus capability, you would only need to alter the source code and implement the new CAN-bus message:

*https://forbes-automotive.com/products/speedpulser-pro
*https://github.com/adamforbes92/speedPulserPro

==CAN-bus: What is this sorcery?==
CAN-bus is a network used by modules to transmit data/information with each other. With only two wires, you can transmit a multitude of messages between modules ([[wikipedia:Multiplexing|multiplexing]]).

In the past, you would have a single wire for every input. In those instances, every button of your cruise control switch has its own signal wire.

The '''objective''' of the CAN-bus emulation is to take all those signals, feed them into your microcontroller and output CAN-bus messages that the ECU will understand, as if it was on a factory MK5/MK6 2.5 chassis.

CAN-bus messages required:

#State of the cruise control switch (Ex.: Main switch, SET, RES, etc.), normally provided by the '''steering column module'''
#Vehicle speed, normally provided by the '''ABS module'''

==Vehicle speed acquisition==
The vehicle speed can be retrieved through the following means:

*GPS module
*VSS sensor
*Hall-effect sensor mounted into the instrument cluster to read the speed of the speedometer cable
*There are more ways to gather this information depending on your creativity

==Emulating the cruise control switch==
The ECU receive the cruise control switch information through the CAN message '''0x38A'''. Here is a detailed description of this CAN message
{| class="wikitable sortable" style="width:100%;"
|+ID '''0x38A''', '''4 bytes''', Sent every '''20 ms'''
!Signal!!Byte!!Start bit!!Bits!!Range / Values!!Notes
|-
|Checksum (See below)||1||0||8||0..255 (Phys = Hex)||—
|-
|Main switch||2||0||1||0 = OFF 1 = ON||Latching ON/OFF
|-
|Tip switch OFF||2||1||1||0 = not pressed 1 = pressed||—
|-
|Tip switch DECEL||2||2||1||0 = not pressed 1 = pressed||—
|-
|Tip switch ACCEL||2||3||1||0 = not pressed 1 = pressed||—
|-
|Cruise decelerate (hold)||2||4||1||0 = not decelerating 1 = decelerating||—
|-
|Cruise accelerate (hold)||2||5||1||0 = not accelerating 1 = accelerating||—
|-
|Cruise control stalk error||2||6||1||0 = OK 1 = stalk error||—
|-
|Not used||2||7||1||—||—
|-
|Tip switch SET||3||0||1||0 = not pressed 1 = pressed||—
|-
|Tip switch RESUME||3||1||1||0 = not pressed 1 = pressed||—
|-
|Sender coding||3||2||2||00 = Body network 01 = Steering column module 10 = Engine||Values per spec
|-
|Message counter||3||4||4||0..15 (Phys = Hex)||Rolling counter
|-
|Not used||4||0||8||—||Byte 4 unused
|}

===Checksum===
The checksum is a formula used to validate the integrity of the message, and detect possible data corruption during the transmission of the message. If the checksum does not match the data, the ECU might reject the message. (Implausible message)

[[File:Checksum GRAneu.png|747x747px]]

This checksum is calculated only with Exclusive OR ([[wikipedia:Exclusive_or|XOR]]) operations

===Code example===
This is a very rough sketch to show a possible implementation. This example would be for an Arduino controller using a MCP2515 shield (hat).
// demo: Cruise control switch, analog to can-bus message for VW PQ35
// Very rough sketch, but should work. Feel free to improve

#include <SPI.h>

#define CAN_2515

// Set SPI CS Pin according to your hardware

#if defined(SEEED_WIO_TERMINAL) && defined(CAN_2518FD)
const int SPI_CS_PIN = BCM8;
const int CAN_INT_PIN = BCM25;
#else

// For Arduino MCP2515 Hat:
// 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;
const int CAN_INT_PIN = 2;
#endif

#ifdef CAN_2518FD
#include "mcp2518fd_can.h"
mcp2518fd CAN(SPI_CS_PIN); // Set CS pin
#endif

#ifdef CAN_2515
#include "mcp2515_can.h"
mcp2515_can CAN(SPI_CS_PIN); // Set CS pin
#endif

const int buttonMain = 4;
const int buttonRes = 2;
const int buttonSet = 0;

byte oldSwitchState = 0x0;
byte sequence = 0x0;

void setup() {
SERIAL_PORT_MONITOR.begin(115200);
while(!Serial){};

while (CAN_OK != CAN.begin(CAN_500KBPS)) { // init powertrain can bus : baudrate = 500k
SERIAL_PORT_MONITOR.println("CAN init fail, retry...");
delay(100);
}
SERIAL_PORT_MONITOR.println("CAN init ok!");
pinMode(buttonMain, INPUT_PULLUP);
pinMode(buttonRes, INPUT_PULLUP);
pinMode(buttonSet, INPUT_PULLUP); // default state 12v
}

void loop() {

byte switchState = 0x0;

// Read analog inputs
int stateMain = digitalRead(buttonMain);
int stateRes = digitalRead(buttonRes);
int stateSet = digitalRead(buttonSet);

// You can more inputs and adjust the logic according the the can-bus chart
if (stateMain == LOW) {
switchState |= (1 << 0); // Set bit 0
}
if (stateSet == LOW) {
switchState |= (1 << 1); // Set bit 1
}
if (stateRes == LOW) {
switchState |= (1 << 2); // Set bit 2
}

// Check if the switch state has changed
if (switchState != oldSwitchState) {
Serial.println(switchState); // Print new state for monitoring purposes
oldSwitchState = switchState; // Update oldSwitchState
}

// Define bytes for can message (0x38A)
byte byteTwo = switchState & 1;

byte byteThree = switchState >> 1;
byteThree = byteThree | 0xC; // Could also be 0x4 (See Sender coding)
byteThree = (sequence << 4) | byteThree;

byte checksum = byteTwo ^ byteThree;

unsigned char payload[4] = {checksum, byteTwo, byteThree, 0x00};
CAN.sendMsgBuf(0x38A, 0, 4, payload);

sequence = (sequence + 1) & 0x0F; // increment for the next frame

delay(20); // Send every 20ms
}