= hal_pi_gpio(9)

== NAME
hal_pi_gpio - enable gpio pins on Raspberry Pi single board computers

== SYNOPSIS

*loadrt hal_pi_gpio    dir*=directionBitField *exclude*=exclusionBitField

== DESCRIPTION

*hal_pi_gpio* is a realtime Hal component that exposes gpio pins of
a RaspberryPi SBC.

The device must use the BCM2835 chip, so these models should work

Models A, B, B+, the Compute Module, and the Raspberry Pi Zero.

Only inputs and output pins are managed by *hal_pi_gpio*.

The driver refers to the pins by their *gpio* number, not by
the SBC header pin number.

NB: The Raspberry Pi is a 3.3V device. 
This means it can not tolerate 5V on any of its pins

== OPTIONS

*dir*=directionBitField 

    Sets the direction of the used pins as Input or Output.
   
     The *directionBitField* is a decimal number that, in 
    binary, is large enough to describe the pins used. The
    binary representation of *dir* will have a '1' for an
    *output* and '0' for an *input*.
    
*exclude*=exclusionBitField

    Excludes pins from being managed by *hal_pi_gpio*.
    
     Some pins may be excluded, leaving them available for
    other purposes ( maybe I2C or SPI or ... ).
     This bitfield marks pins as excluded from *hal_pi_gpio*.
    A '1' in the bitfield means excluded, a '0' means the 
    pin is to be managed by *hal_pi_gpio*.
    
    These bitfileds can be daunting, so user 'twoflowers' wrote this:
    
    https://forum.linuxcnc.org/media/kunena/attachments/17065/hal_pi_gpio-calculator.sh.gz

== FUNCTIONS

*hal_pi_gpio*.::
A single function is created. Only 1 RaspberryPi is allowed.


*hal_pi_gpio.read()*
Makes available the values read from all the non excluded inputs.



*hal__pi_gpio.write()* 
Updates all the non-excluded output pins.


== PINS
*hal_pi_gpio*.pin.NN.in

*hal_pi_gpio*.pin.NN.out

== SEE ALSO

*hm2_rpspi*(1)

== BUGS

Bug: Not specified as singleton yet allows only 1 instance
Enhancements: Maybe multiple devices
	      Maybe reset type outputs, 
	       allowing faster software stepping.
	      Bitfields are not man readable,
	       so a simpler method to set options.

== AUTHOR

Author: Michael Haberler
License: GPL Version 2
Copyright (c) 2012.

some code  taken from the bcm2835 library by::

Author: Mike McCauley (mikem@open.com.au)
Copyright (C) 2011 Mike McCauley
see http://www.open.com.au/mikem/bcm2835/
Copyright (c) 2012 Ben Croston - cpuinfo.*


Improvements by several other members of the LinuxCNC development team.



== REPORTING BUGS
Report bugs to 


== COPYRIGHT
License: GPL Version 2
Copyright (c) 2012 Michael Haberler

This is free software; see the source for copying conditions.  

There is NO warranty; not even for MERCHANTABILITY or 
FITNESS FOR A PARTICULAR PURPOSE.