Re: gpio(4) and pulsing pins in software

[Reinoud Zandijk <reinoud%NetBSD.org@localhost>]

Hi Marc,

On Wed, Sep 28, 2011 at 10:05:31PM +0200, Marc Balmer wrote:
> Marc....

sorry :-D

> > On Sun, Sep 25, 2011 at 11:42:11AM +0200, Marc Balmer wrote:
> > I'd like to be able to set the PWM indepentently for each pin! say 
> > specifying
> > 70/256 on and otherwise off.
> 
> That is what gpiopwm(4) is for.
> 
> > gpiopwm(4) can be grouped on pins that needs synchronisation. Say gpiopwm0 @
> > gpio0 has pins 3, 5, 7 with each their pwm's but synchronised on 'on' or 
> > 'off'
> > and gpiopwm1 @ gpio0 has pin 2 and 8. As they are synchronised all the pins
> > attached can be programmed at one go preventing arbitrary races.
> 
> How can you sync if the pins have different duty cycles?

Well they could all start at the same time, say a pin0 @ 70/256 and a pin1 @
45/256 can start both at t=0 and pin1 dropping at t=44 and pin0 dropping at
t=69 and both keeping low until t=256.

The base duty cycle will then be the same for say a gpiopwm0, only different 
portions of the
time on/off for the pins connected to gpiopwn0.

Is this more clear?

With regards,
Reinoud