GPIOPWM(4) | Device Drivers Manual | GPIOPWM(4) |
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:
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>.
November 13, 2011 | NetBSD 10.99 |