GPIOPWM(4) BSD Kernel Interfaces Manual GPIOPWM(4)
NAME
gpiopwm -- support for pulsing GPIO pins in software
SYNOPSIS
gpiopwm* at gpio? offset ? mask 1
gpiopwm* at gpio?
DESCRIPTION
The gpiopwm driver allows for pulsing GPIO pins in software using the callout(9) facility. The pulse frequency and duty cycle are specified
indirectly by setting an ``on'' and ``off'' period, in ticks. Both values are accessible as sysctl(3) variables.
SYSCTL VARIABLES
The following sysctl(3) variables are used to define the pulsing:
hw.gpiopwmN.off
Define the ``off'' period in ticks.
hw.gpiopwmN.on
Define the ``on'' period in ticks.
Only when both the ``on'' and the ``off'' period are set to values higher than zero pulsing will start. To stop the pulsing, set either
value to zero.
EXAMPLES
To pulse a pin on a machine with 100 ticks/second with a frequency of 1Hz and a duty cycle of 20%, the ``on'' period must be set to 20 and
the ``off'' period must be set to 80. The following example will pulse the error LED of a Soekris net4801 with a frequency of 1 Hz and a
duty cycle of 20%:
# gpioctl gpio0 20 set pp
# gpioctl gpio0 attach gpiopwm 20 1
# sysctl -w hw.gpiopwm0.off=80
# sysctl -w hw.gpiopwm0.on=20
SEE ALSO
gpio(4), intro(4), gpioctl(8), sysctl(8)
HISTORY
The gpiopwm driver first appeared in NetBSD 6.0.
AUTHORS
The gpiopwm driver was written by Marc Balmer <marc@msys.ch>.
BSD
November 13, 2011 BSD
