This is a simple daemon that facilitates access to the Raspberry Pi (RPi) GPIO ports from processes that are not running as root. This daemon, running as root, waits for connections on a Unix domain socket and implements a very simple command/response protocol to permit input and output from the GPIO ports. A typical application would be for a Web CGI script that needs access to the GPIO interface, since it's strongly advised not to run a web server as root.

• python-daemon 1.5.5
• raspberry-gpio-python 0.5.0

• All commands are initiated by the client program and are terminated by a newline character.
• port is the pin number on the RPi connector, not the Broadcom channel number.
• One response is generated per command, also terminated by a newline character.
• Commands are case-independent.
• Lines beginning with # are treated as comments

SETUP port OUT [LOW|HIGH]

Sets port as output. Optional parameter LOW or HIGH specifies the initial state of the port. Responds with 'ok' or an error message.

SETUP port IN [PULLUP|PULLDOWN]

Sets port as input. Optional parameter PULLUP or PULLDOWN specifies whether a pull up or pull down resistor is configured on the port; the default is no pull up or pull down. Responds with 'ok' or an error message.

OUTPUT port LOW|HIGH

Sets the state of the specified output port, and responds with 'ok' or an error message.

INPUT port

Reads the specified input port, and responds with its state: 'true' or 'false' or an error message.

SETUP 16 IN PULLUP
OUTPUT 11 HIGH
INPUT 16

• Copy gpiod.py to a suitable location, such as /usr/local/sbin
• copy gpiod (the init script) to /etc/init.d
• Ensure that the modules listed above under Python Requirements have been installed
• Start the daemon and test with gpiotest.py
• If you want to initialize the interface when the daemon starts, create a script with gpiod commands at /etc/gpiod.cfg

Some ideas for enhancements include:

• More comprehensive support of the GPIO port capabilities, such as event detection (although this may also imply changes to the socket protocol).
• Better initialization using a pidfile
• Ability to specify a duration for timed output pulses

• Initial version