What is it?

This product works as a data bridge between a car’s OBD port and Arduino (or similar hardware) with a dedicated open-source library provided. It provides high-speed OBD-II data access and integrates 9-DOF motion sensor with built-in sensor fusion algorithm. The adapter is powered directly from OBD port and outputs regulated 5V voltage for powering attached devices.

Features

• Access to all standard OBD-II PIDs with ELM327 AT command-set
• Reading and clearing vehicle diagnostic trouble codes (engine & powertrain only)
• Measuring car battery voltage
• Built-in MPU-9250 9-DOF motion sensor
• Built-in quaternion sensor fusion algorithm for precise orientation measurement
• Supplying power for host device (5V up to 2.1A)
• Serial UART data interface compatible with both 3.3V and 5V micro-controllers
• Micro USB port for computer/tablet OBD-II access and firmware upgrade
• Arduino library and example sketches available
• Low power mode @6mA

Compatibility

The adapter plugs into the OBD port usually located under the steering column or slightly to the left of it. To check if your vehicle is OBD-II certified, open your hood and find the sticker that looks like this:

Vehicles using following vehicle protocols are supported.

• CAN 500Kbps/29bit
• CAN 500Kbps/11bit
• CAN 250Kbps/29bit
• CAN 250Kbps/11bit
• KWP2000 Fast
• KWP2000 5Kbps
• ISO9141-2 (Partial)

Connectors

The adapter stays plugged into the OBD port usually located under the steering column or slightly to the left of it. A unpluggable cable comes out from the adapter and splits into one 4-pin connector two 2-pin connectors, including power lines (VCC/GND) and data lines (Rx/Tx). They can be connected to Arduino with onboard breakout pins or breakout shield. Your Arduino device will look tidy in car with only one cable.

Power Connector (2-pin 2.54 Dupont connector)

Red: VCC (connecting to Arduino’s VCC)
Black: GND (connecting to Arduino’s GND)

Serial UART Data Connector (2-pin 2.54 Dupont connector)

White: Rx (connected to Arduino’s serial Tx)
Green: Tx (connected to Arduino’s serial Rx)

Note: Arduino UNO or Nano only has one hardware serial which is also used by USB serial. Avoid using serial output if the adapter is connected to hardware serial. Arduino Leonardo, Mega, Due do not have this limit.

USB Port

For connection with computer or tablet via micro USB cable
Allows power output (5V/2A)

Extended Command Set

We have extended standard ELM327 command set for following purposes:

Reading built-in MEMS motion sensor data
Reading orientation result from sensor fusion computation
Reading measured car battery voltage

Following are the added commands:

ATACL

Function: reading accelerometer data
Response format: X,Y,Z (in G)

ATGYRO

Function: reading gyroscope data
Response: X,Y,Z (in degree)

ATMAG

Function: reading magnetometer data
Response: X,Y,Z (in milli-Gauss)

ATTEMP

Function: reading temperature data
Response: temperature (raw) data

ATRV

Function: reading car battery voltage
Response: voltage value

ATQU0/ATQU1

Function: disable/enable 9-DOF sensor fusion (disabled by default)
Response: OK

ATORI

Function: retrieving orientation parameters from 9-DOF sensor fusion
Response: ,, (in degree)

Library

A dedicated Arduino library is provided for easy access to all the features with any type of Arduino.

Some commonly used APIs are like following:

setBaudRate – set adapter serial baudrate
readPID – read specified OBD-II PID and return parsed value
clearDTC – clear diagnostic trouble code
getVoltage – measure car battery voltage
getVIN – retrieve Vehicle Identification Number
getTemperature – get device temperature
readAccel – read accelerometer X/Y/Z values
memsInit – initialize motion sensor
memsRead – read motion sensor data
memsOrientation – retrieve computed orientation data

Example sketches are available here.

Some commonly used PIDs are defined in OBD library as following.

Engine

PID_RPM – Engine RPM (rpm)
PID_ENGINE_LOAD – Calculated engine load (%)
PID_COOLANT_TEMP – Engine coolant temperature (°C)
PID_ENGINE_LOAD – Calculated Engine load (%)
PID_ABSOLUTE_ENGINE_LOAD – Absolute Engine load (%)
PID_TIMING_ADVANCE – Ignition timing advance (°)
PID_ENGINE_OIL_TEMP – Engine oil temperature (°C)
PID_ENGINE_TORQUE_PERCENTAGE – Engine torque percentage (%)
PID_ENGINE_REF_TORQUE – Engine reference torque (Nm)

Intake/Exhaust

PID_INTAKE_TEMP – Intake temperature (°C)
PID_INTAKE_PRESSURE – Intake manifold absolute pressure (kPa)
PID_MAF_FLOW – MAF flow pressure (grams/s)
PID_BAROMETRIC – Barometric pressure (kPa)

Speed/Time

PID_SPEED – Vehicle speed (km/h)
PID_RUNTIME – Engine running time (second)
PID_DISTANCE – Vehicle running distance (km)

Driver

PID_THROTTLE – Throttle position (%)
PID_AMBIENT_TEMP – Ambient temperature (°C)

Electric Systems

PID_CONTROL_MODULE_VOLTAGE – vehicle control module voltage (V)
PID_HYBRID_BATTERY_PERCENTAGE – Hybrid battery pack remaining life (%)

Additional defines can be added to access all OBD-II PIDs which the car’s ECU provides.