Custom Commands

If the command you need is not in python-OBDs tables, you can create a new OBDCommand object. The constructor accepts the following arguments (each will become a property).

Argument	Type	Description
name	string	(human readability only)
desc	string	(human readability only)
mode	string	OBD mode (hex)
pid	string	OBD PID (hex)
bytes	int	Number of bytes expected in response
decoder	callable	Function used for decoding the hex response
supported (optional)	bool	Flag to prevent the sending of unsupported commands (False by default)

When the command is sent, the mode and pid properties are simply concatenated. For unusual codes that don't follow the mode + pid structure, feel free to use just one, while setting the other to an empty string.

The decoder argument is a function of following form.

	def <name>(_hex):
		...
		return (<value>, <unit>)

The _hex argument is the data recieved from the car, and is guaranteed to be the size of the bytes property specified in the OBDCommand.

For example:

from obd import OBDCommand
from obd.utils import unhex

def rpm(_hex):
	v = unhex(_hex) # helper function to convert hex to int
	v = v / 4.0
	return (v, obd.Unit.RPM)

c = OBDCommand("RPM", "Engine RPM", "01", "0C", 2, rpm)