gpio/gpio.1

.TH "GPIO" "21st October 2012" "Command-Line access to Raspberry Pi and PiFace GPIO"

.SH NAME
gpio \- Command-line access to Raspberry Pi and PiFace GPIO

.SH SYNOPSIS
.B gpio
.B \-v
.PP
.B gpio
.B [ \-g ]
.B read/write/wb/pwm/mode ...
.PP
.B gpio
.B [ \-p ]
.B read/write/wb
.B ...
.PP
.B gpio
.B readall
.PP
.B gpio
.B unexportall/exports
.PP
.B gpio
.B export/edge/unexport
.B ...
.PP
.B gpio
.B drive
group value
.PP
.B gpio
.B pwm-bal/pwm-ms
.PP
.B gpio
.B pwmr
range
.PP
.B gpio
.B load \ i2c/spi
.PP
.B gpio
.B gbr
channel
.PP
.B gpio
.B gbw
channel value

.SH DESCRIPTION

.B GPIO
is a swiss army knife of a command line tool to allow the user easy
access to the GPIO pins on the Raspberry Pi and the SPI A/D and D/A
converters on the Gertboard. It's designed for simple testing and
diagnostic purposes, but can be used in shell scripts for general if
somewhat slow control of the GPIO pins.

It can also control the IO's on the PiFace IO board and load the SPI and I2C
kernel modules if required.

Additionally, it can be used to set the exports in the \fI/sys/class/gpio\fR
system directory to allow subsequent programs to use the \fR/sys/class/gpio\fR
interface without needing to be run as root.

.SH OPTIONS

.TP
.B \-v
Output the current version including the board revision of the Raspberry Pi.

.TP
.B \-g
Use the BCM_GPIO pins numbers rather than wiringPi pin numbers.
\fINOTE:\fR The BCM_GPIO pin numbers are always used with the 
export and edge commands.

.TP
.B \-p
Use the PiFace interface board and its corresponding pin numbers.

.TP
.B read <pin>
Read the digital value of the given pin and print 0 or 1 to represent the
respective logic levels.

.TP
.B write <pin> <value>
Write the given value (0 or 1) to the pin. You need to set the pin
to output mode first.

.TP
.B wb <value>
Write the given byte to the 8 main GPIO pins. You can prefix it with 0x
to specify a hexadecimal number. You need to set pins to output mode
first.

.TP
.B readall
Output a table of all GPIO pins values. The values represent the actual values read
if the pin is in input mode, or the last value written if the pin is in output
mode.

.TP
.B pwm <pin> <value>
Write a PWM value (0-1023) to the given pin.

.TP
.B mode <pin> <mode>
Set a pin into \fIinput\fR, \fIoutput\fR or \fIpwm\fR mode. Can also
use the literals \fIup\fR, \fIdown\fR or \fItri\fR to set the internal
pull-up, pull-down or tristate (off) controls.

.TP
.B unexportall
Un-Export all the GPIO pins in the /sys/class/gpio directory.

.TP
.B exports
Print a list (if any) of all the exported GPIO pins and their current values.

.TP
.B export
Export a GPIO pin in the \fI/sys/class/gpio\fR directory. Use like the
mode command above however only \fIin\fR and \fIout\fR are supported at
this time. Note that the pin number is the \fBBCM_GPIO\fR number and
not the wiringPi number.

Once a GPIO pin has been exported, the \fBgpio\fR program changes the
ownership of the \fI/sys/class/gpio/gpioX/value\fR and if present in
later kernels, the \fI/sys/class/gpio/gpioX/edge\fR pseudo files to
that of the user running the \fBgpio\fR program. This means that you
can have a small script of gpio exports to setup the gpio pins as your
program requires without the need to run anything as root, or with the
sudo command.

.TP
.B edge
This exports a GPIO pin in the \fI/sys/class/gpio\fR directory, set
the direction to input and set the edge interrupt method to \fInone\fR,
\fIrising\fR, \fIfalling\fR or \fIboth\fR.  Use like the export command
above and note that \fBBCM_GPIO\fR pin number is used not not wiringPi pin
numbering.

Like the export commands above, ownership is set to that of the 
calling user, allowing subsequent access from user programs without
requiring root/sudo.

.TP
.B unexport
Un-Export a GPIO pin in the /sys/class/gpio directory.

.TP
.B drive
group value

Change the pad driver value for the given pad group to the supplied drive
value. Group is 0, 1 or 2 and value is 0-7. Do not use unless you are
absolutely sure you know what you're doing.

.TP
.B pwm-bal/pwm-ms 
Change the PWM mode to balanced (the default) or mark:space ratio (traditional)

.TP
.B pwmr
Change the PWM range register. The default is 1024.

.TP
.B load i2c/spi
This loads the i2c or the spi drivers into the system and changes the permissions on
the associated /dev/ entries so that the current user has access to them.

.TP
.B gbr
channel

This reads the analog to digital converter on the Gertboard on the given
channel. The board jumpers need to be in-place to do this operation.

.TP
.B gbw
channel value

This writes the supplied value to the output channel on the Gertboards
SPI digital to analogue converter.
The board jumpers need to be in-place to do this operation.


.SH "WiringPi vs. BCM_GPIO Pin numbering"

.PP
.TS
r r r l.
WiringPi	GPIO-r1	GPIO-r2	Function
_
0	17	17
1	18	18	(PWM)
2	21	27
3	22	22
4	23	23
5	24	24
6	25	25
7	4	4
8	0	2	I2C: SDA0
9	1	3	I2C: SCL0
10	8	8	SPI: CE0
11	7	7	SPI: CE1
12	10	10	SPI: MOSI
13	9	9	SPI: MISO
14	11	11	SPI: SCLK
15	14	14	TxD
16	15	16	RxD
17	-	28
18	-	29
19	-	30
20	-	31
.TE

Note that "r1" and "r2" above refers to the board revision. Normally
wiringPi detects the correct board revision with use for it's own
numbering scheme, but if you are using a Revision 2 board with some
of the pins which change numbers between revisions you will need
to alter your software.

.SH FILES

.TP 2.2i
.I gpio
executable

.SH EXAMPLES
.TP 2.2i
gpio mode 4 output # Set pin 4 to output
.PP
gpio -g mode 23 output # Set GPIO pin 23 to output (same as WiringPi pin 4)
.PP
gpio mode 1 pwm # Set pin 1 to PWM mode
.PP
gpio pwm 1 512 # Set pin 1 to PWM value 512 - half brightness
.PP
gpio export 17 out # Set GPIO Pin 17 to output
.PP
gpio export 0 in # Set GPIO Pin 0 (SDA0) to input.
.PP
gpio -g read 0 # Read GPIO Pin 0 (SDA0)

.SH "NOTES"

When using the \fIexport\fR, \fIedge\fR or \fIunexport\fR commands, the
pin numbers are \fBalways\fR native BCM_GPIO numbers and never wiringPi
pin numbers.

.SH "SEE ALSO"

.LP
WiringPi's home page
.IP
https://projects.drogon.net/raspberry-pi/wiringpi/

.SH AUTHOR

Gordon Henderson

.SH "REPORTING BUGS"

Please report bugs to <projects@drogon.net>

.SH COPYRIGHT

Copyright (c) 2012 Gordon Henderson
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

.SH TRADEMARKS AND ACKNOWLEDGEMENTS

Raspberry Pi is a trademark of the Raspberry Pi Foundation.