OBD2 to MQTT Bridge

Following Jaguar Land Rover's recent lockdown of their API, I put this script together to help at least get EV State of Charge and other basic data from an I-Pace when it is connected to the home WiFi. The script basically provides a bridge between a WiFi version of an ELM327 OBD-II interface, such as the VGate iCar Pro, and an MQTT broker, such that the data can then be used by home automation systems, such as openHAB.

Credit to dconlon for his wifi version of the OBD python library.

Requirements

Python 3.6+
paho-mqtt
configparser
pint
WiFi version of the OBD library from https://github.com/dconlon/icar_odb_wifi

Installation

Clone this repository:

git clone https://github.com/yourusername/obd2mqtt.git
cd obd2mqtt

Install the required Python packages:

pip install paho-mqtt configparser pint

Install the WiFi version of the OBD library:

pip install git+https://github.com/dconlon/icar_odb_wifi.git

Copy the sample configuration file and modify it according to your setup:
```
cp obd2mqtt.cfg.sample obd2mqtt.cfg
```

Configuration

Edit the obd2mqtt.cfg file to set up your MQTT broker details and OBD-II interface:

[MQTT]
MQTT_SERVER = your_mqtt_broker_address
MQTT_SUB_TOPIC = obd2mqtt/commands
MQTT_PUB_TOPIC = obd2mqtt/data
MQTT_USER = your_mqtt_username
MQTT_PASSWORD = your_mqtt_password

[OBD]
OBD_PORT = your_obd_wifi_address

[MISC]
DEBUG = False

Usage

Run the script:

python obd2mqtt.py

The script will connect to the OBD-II's WiFi interface and the MQTT broker. It will then listen for commands on the specified MQTT subscription topic and publish vehicle data to the publication topic.

PIDs

The obd2_pids.csv file includes an initial set of PIDs from a Jaguar I-Pace.

This file can be customised as required for the PIDs supported by whatever vehicle the OBD is connected to. Each line should contain the following fields:

pid,name,description,decoder_function,units

The docoder_function is the name of the function to decode the type of data returned by the obd library. The current decoder functions included (over and above those built-in into the obd library such as raw_string) are ones I needed for decoding the PIDs from the I-Pace:

Function Name            | Description
-------------------------|----------------------------------------------------------
decode_int               | Decodes response as an integer (A)
decode_int_divide_by_2   | Decodes response as an integer divided by 2 (A/2)
decode_int_divide_by_10  | Decodes response as an integer divided by 10 (A/10)
decode_int_divide_by_100 | Decodes response as (256*A + B)/100
decode_int_divide_by_108 | Decodes response as an integer divided by 108 (A/108)
decode_int_divide_by_1000| Decodes response as (256*A + B)/1000
decode_temperature       | Decodes response as temperature in Celsius (A-40)
decode_temperature2      | Decodes response as temperature in Celsius (A/2-40)
decode_temperature3      | Decodes response as temperature in Celsius (A-50)
decode_current           | Decodes response as current in amps ((A*256+B-32768)/40)
decode_location          | Decodes response as GPS latitude and longitude

Note:

A, B represent the first and second bytes of the OBD-II response, respectively.
These functions handle different scaling factors and offsets as used for the I-Pace PIDs given.

MQTT Commands

To interact with the OBD2 to MQTT Bridge, JSON-formatted commands can be published to the MQTT subscription topic as specified in the configuration file (default is ipace/obd2mqtt/_system/send_command).

Available Commands:

refresh_all: Queries all standard set of PIDs and publish their values.
```
{"command": "refresh_all"}
```
available_commands: Lists all available OBD commands.
```
{"command": "available_commands"}
```
reload_pids: Reloads the PIDs from the PIDs csv file.
```
{"command": "reload_pids"}
```
set_obd_mode: Enables or disables the OBD interface power saving (i.e. leave the OBD2 device permanently on, or allow to go to sleep). Please see the comments to the code for this, as there the actual AT command value can be tweaked depending on what is required.
```
{
  "command": "set_obd_mode",
  "mode": "enable"  // or "disable"
}
```
Custom OBD Commands: Query the value of any single PID from the csv file using its "name".
```
{"command": "RPM"}  // Example: Get engine RPM
```

custom: Sends a custom PID command.

{
  "command": "custom",
  "definition": {
    "name": "CustomCommand",
    "desc": "Description of the command",
    "pid": "ABCD",
    "decoder": "decode_int",
    "units": "rpm"
  }
}

NOTE pid and decoder are mandatory when sending custom PID commands

Contributing

The script seems to be working for my purposes, and so I am not intending to spend much time developing it further. Contributions are however always welcome; please feel free to submit a Pull Request!

License

This project is licensed under the MIT License.

smar000/obd2mqtt