This code is for the Arduino Uno with a 16x2 Display Shield. [WORKING]
For the Arduino Mega with a TFT LCD Display Shield look into this repo [NOT WORKING YET]
Simple trip computer for the Arduino Uno with a 16x2 Screen to display useful information in all VAG vehicles with the MARELLI 4LV ECU (VAG Number: 036906034AM). This includes most Golf mk4/Jetta/Bora from the years around 2000 that are limited to the K-Line communication and the KW1281 protocol. Newer cars since around 2005 began to adapt OBD-2 with CAN communication, that can be accessed through a ELM327 controller. No such simple controller exists currently for KKL.
This repo contains all necessary files. The only file containing code is obdisplay.cpp.
- Supported baud rates 1200, 2400, 4800, 9600, 10400
- Supports KWP1281 K-Line through NewSoftwareSerial
- 3 operating modes: Acknowledge, Group reading, Sensors reading
- Read, view and delete DTC Errors
- Supported ECU addr 0x01(engine) and 0x17(dashboard)
- Automatic communication error handling
- Simulation mode to test the display
- KWP1281 exit procedure
Requirements: Arduino Uno, 16x2 Liquidcrystal Display Shield, Autodia K409 KKL OBD to USB cable
Look inside the OBD cable and note which MCU is placed (E.g. FT232R or FT232RQ), get its datasheet, find the RXD and TXD pins, solder the first visible contact point to your Arduino digital pins of your liking (Here: 2 and 3) and cut both lines after the contact point. Don't forget to solder the +5V and GROUND from your Arduino to the OBD cable MCU (Just use the USB stripped male on the platine) since without it no communication is possible. You should have 4 cables connected between your OBD cable and your Arduino and a seperate USB or power souce input to power the Arduino and access its Serial debug communication.
See the pictures below for visual guidance.
Refer to the linked git repo for pictures and a bit more info.
Open the project with platformIO and a programming environment of your chase (VSCode) and flash it to your arduino. If your ECU differs from the 036906034AM ECU you may need to assess your Label files and rewrite a portion of the code to work with your ECU. See below for more information on label files. Each Address may have a different baud rate (E.g. 0x01 baud 9600 while 0x17 baud 10400). Older ECU's (<1997) may use very slow baud rates like 1200 or 2400, while newer ECU's (>1997) most often use baud rates around 9600 and 10400. I have not encountered baud 4800 yet.
To initialize a connection through OBD KWP1281 K-Line send a 5 baud init, acknowledge the sync bytes and receive the connect blocks. Make sure you don't IDLE in this phase or else the ECU may do nonsense.
After initialization you can select 3 KWP_MODES:
- 0 = Keep connection alive, send acknowledge blocks
- 1 = Read all values from all groups from ECU. (ECU dependent, you may need to adapt to yours)
- 2 = Read the 4 values from one group. (ECU independent, see group menu)
Communication errors can occur which are handled by the code. There may be situations where this is not the case, please open an issue if this happens to you.
Manual exit, DTC read and delete blocks are only send if the user manually presses the specified UI button.
The measurement groups of each ECU Addres contain 4 values. Each different version of each car may have a different order of values and different values to obtain. To know which groups display which values you either need to search for your cars Label File "xxx-xxx-xxx.LBL" or hook up VCDS (or any other software to display measurement groups) and record your display while clicking through the groups to get a rough image what these values correspond to.
Here are the values for the 036906034AM MARELLI ECU for the 1.6 16V Engine, which partly does not contain label files:
const uint8_t ADDR_ENGINE = 0x01;
// Label File: None
// Measurement Blocks - 0x08:
// Group 00: 1-10 with 3 digit numbers
// Group 01: 0 /min RPM, 17.0°C Temperature, 0.0% Lambda, 10110010 Binary Bits **
// Group 02: 0 /min RPM, 0.0% Load, 0.0ms Time Correction, 1012.0 mbar Absolute Pressure
// Group 03: 0 /min RPM, 1012.0 mbar Absolute Pressure, 5.4° T.B. Angle, 0.0° Steering Angle **
// Group 04: 0 /min RPM, 11.70 V Voltage, 17.0°C Temperature, 14°C Temperature **
// Group 05: 0 /min RPM, 0.0% Load, 0.0 km/h Speed, Part Throttle NA
// Group 06: 0 /min RPM, 0.0% Load, 14°C Temperature, -1.0% Lambda **
// Group 14: 0 /min RPM, 0.0% Load, 0.0 no units, Enabled NA
// Readiness - 0x15:
// Readiness Status: 10100101
// Exhaust Gas Recirculation: Failed or Incomplete
// Oxygen Sensor Heating: Passed
// Oxygen Sensor(s): Failed or Incomplete
// Air Conditioning: Passed
// Secondary Air Injection: Passed
// Evaporative Emissions: Failed or Incomplete
// Catalyst Heating: Passed
// Catalytic Converter(s): Failed or Incomplete
const uint8_t ADDR_ABS_BRAKES = 0x03; // UNUSED
// Label File: None
// Measurement Blocks - 0x08:
// Group 4: 0.00° Steering Angle, 0.31 m/s^2 Lateral Acceleration, -0.36°/s Turn Rate, N/A
// Group 5: -1.27 bar Pressure, 0.42 bar Pressure, N/A, N/A
const uint8_t ADDR_AUTO_HVAC = 0x08; // UNUSED
// Label File: 381-907-044.LBL
// Measurement Blocks - 0x08:
// Group 1: 8.0 A/C clutch sw-off cond. 1-12, 0.0 Eng. speed recog (0=no, 1=yes), 0.0 km/h Road Speed, 121.0 Standing time (0-240min.)
// Group 2: 42.0 Measured Value, 42.0 Specified Value, 219.0 Position: air supply cooled, 42.0 Position: air supply heated
// Group 3: 221.0 Measured Value, 221.0 Specified Value, 221.0 Position: air flow to panel, 40.0 Position: air flow to footwell
// Group 4: 223.0 Measured Value, 223.0 Specified Value, 223.0 Position: air flow to footwell, 39.0 Position: air flow to defroster
// Group 5: 237.0 Measured Value, 234.0 Specified Value, 234.0 Position: fresh air, 30.0 Position: recirculating
// Group 6: 0.0°C Temp displayed on panel, 7.0°C Temp. air intake duct, 0.0°C Outside air temperature, 0.0% Sun photo sensor (0-120%)
// Group 7: 0.0 Outlet temp. panel (G191), 5.0°C Outlet temp. floor (G192), 3.0°C Panel temp. near LCD (G56), 0.0 n/a
// Group 8: 0.00V Specif. Voltage air blower, 0.28V Measured Voltage air blower, 12.18V Measured Voltage A/C clutch, 0.0 no units
const uint8_t ADDR_INSTRUMENTS = 0x17;
// Label File: 1J0-920-xx0.LBL
// Measurement Blocks - 0x08:
// Group 1: 0.0 km/h Speed, 0 /min Engine Speed, Oil Pr. 2 < min (Oil pressure 0.9 bar), 21:50 Time
// Group 2: 121960 Odometer, 9.0 l Fuel level, 93 ohms Fuel Sender Resistance, 0.0°C Ambient Temperature
// Group 3: 12.0°C Coolant temp., OK Oil Level (OK/n.OK), 11.0°C Oil temp, N/AThanks to many wonderful projects for making this project less painful than it already is.
Blafusel with a detailed overview on the KW1281 protocol and the communication between the microcontroller and the ECU.
mkirbst's existing code helped a lot to get the mainframe going. His code did not work on my car, although he has a very similar one to mine using the same protocol. He refers to some connection problems, which I also got that can only be caused by the software. This project eliminates connection problems by implementing a procedure for error messages by the ECU.
Use this at your own risk. Be cautious. Damaging your car or your cars ECU is possible. Wrong wiring and setup can create a fire hazard. In rare cases the airbags can deploy when reading DTC errors on 0x15. The OBD was meant to be a diagnostics port only, by using a tripcomputer through it the workload on the ECU increases.
This is an early version and I'm only releasing it to help on anyones journey with this VAG mess. You need to manually remove connections and solder cables on an OBD to USB board and hook them up to the Arduino Uno TX and RX pins. You need to turn ignition ON for the ECU to start. This software should not break anything in the ECU, since only the measure groups are accessed. Depending on your car, you may need to adapt this code for various values.
Be careful when working with the Airbag Address 0x15 since in some rare circumstances when an electrical failure is given in the airbag system and DTC error codes are deleted the airbag can deploy on affected ECU's. I would hardly advise not to touch the Airbag controller with selfmade code.
This project may work with other Arduino's, Displays, OBD cables and VAG cars.
If you have questions feel free to open an issue and paste your Serial log there.
Contributions are welcomed.
I'm not planning to add the following to this project but feel free to contribute:
- LEDs + Sound on critical warnings (Oil pressure, temperature too high, DTC errors)
- Adaptation support
- Login support
- Save read_connect_blocks() info about ECU and display it
- Memory optimizations