pigpio/README.md

pigpio

pigpio is a C library for the Raspberry which allows control of the General Purpose Input Outputs (GPIO).

Features

• Sampling and time-stamping of GPIO 0-31 between 100,000 and 1,000,000 times per second
• Provision of PWM on any number of the user GPIO simultaneously
• Provision of servo pulses on any number of the user GPIO simultaneously
• Callbacks when any of GPIO 0-31 change state (callbacks receive the time of the event accurate to a few microseconds)
• Notifications via pipe when any of GPIO 0-31 change state
• Callbacks at timed intervals
• Reading/writing all of the GPIO in a bank (0-31, 32-53) as a single operation
• Individually setting GPIO modes, reading and writing
• Socket and pipe interfaces for the bulk of the functionality in addition to the underlying C library calls
• Construction of arbitrary waveforms to give precise timing of output GPIO level changes (accurate to a few microseconds)
• Software serial links, I2C, and SPI using any user GPIO
• Rudimentary permission control through the socket and pipe interfaces so users can be prevented from "updating" inappropriate GPIO
• Creating and running scripts on the pigpio daemon

Interfaces

The library provides a number of control interfaces

• the C function interface,
• the /dev/pigpio pipe interface,
• the socket interface (used by the pigs utility and the Python module).

Utilities

A number of utility programs are provided:

• the pigpiod daemon,
• the Python module,
• the piscope digital waveform viewer,
• the pigs command line utility,
• the pig2vcd utility which converts notifications into the value change dump (VCD) format (useful for viewing digital waveforms with GTKWave).

Example programs

See http://abyz.co.uk/rpi/pigpio/examples.html.

GPIO

ALL GPIO are identified by their Broadcom number. See http://elinux.org.

There are 54 GPIO in total, arranged in two banks.

Bank 1 contains GPIO 0-31. Bank 2 contains GPIO 32-54.

A user should only manipulate GPIO in bank 1.

There are at least three types of board:

• Type 1
  • 26 pin header (P1)
  • Hardware revision numbers of 2 and 3
  • User GPIO 0-1, 4, 7-11, 14-15, 17-18, 21-25
• Type 2
  • 26 pin header (P1) and an additional 8 pin header (P5)
  • Hardware revision numbers of 4, 5, 6, and 15
  • User GPIO 2-4, 7-11, 14-15, 17-18, 22-25, 27-31
• Type 3
  • 40 pin expansion header (J8)
  • Hardware revision numbers of 16 or greater
  • User GPIO 2-27 (0 and 1 are reserved)

It is safe to read all the GPIO. If you try to write a system GPIO or change its mode you can crash the Pi or corrupt the data on the SD card.