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NetBSD 6.1.5 - man page for gpiopwm (netbsd section 4)

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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
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