gpiopwm
—
support for pulsing GPIO pins in software
gpiopwm* at gpio? offset ? mask 1
gpiopwm* at gpio?
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.
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.
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
The gpiopwm
driver first appeared in
NetBSD 6.0.
The gpiopwm
driver was written by Marc
Balmer
<marc@msys.ch>.