pwm for raspberry pi?

[Luiz Otavio O Souza]

On 26 May 2015 at 03:13, Daniel Braniss wrote:
>
>> On May 26, 2015, at 1:14 AM, Luiz Otavio O Souza wrote:
>>
>> On 25 May 2015 at 07:52, Daniel Braniss wrote:
>>> Hi,
>>> Now that I’m rapping up my spi/rfid driver (available on demand :-),
>>> I would like to use the pwm interface to power on/off a lock, but
>>> have no idea how to go around it, so any clues would be mostly welcomed.
>>>
>>> cheers,
>>>        danny
>>
>> The PWM module is quite simple and has only two outputs, they can be
>> used only with recent 40 GPIO pins header (RPi-B+ or RPi2), in the
>> older models only one output was wired.
>>
> I do have a B+
>
>> The bcm2835 peripherals datasheet describes the PWM module registers
>
> I’ve read it, hence I know it’s possible, what I’ missing is how to access it via
> FreeBSD. There is a some mention for the BeagleBoneBlack, but it seems
> broken, the FDT mentions the pins. Too many leads but not enough info
> on how to tie them up :-)
>
> cheers,
>         danny

There is no defined API to access PWM settings ATM, on beaglebone this
is done with sysctls:

dev.am335x_pwm.2.dutyB: 0
dev.am335x_pwm.2.dutyA: 0
dev.am335x_pwm.2.period: 1000
dev.am335x_pwm.2.freq: 100000
dev.am335x_pwm.2.clkdiv: 1
dev.am335x_pwm.2.%parent: simplebus0
dev.am335x_pwm.2.%pnpinfo: name=pwm at 48304000 compat=ti,am335x-pwm
dev.am335x_pwm.2.%location:
dev.am335x_pwm.2.%driver: am335x_pwm
dev.am335x_pwm.2.%desc: AM335x PWM

There are 3 PWM modules, each one with two outputs controlled by dutyA
and dutyB.

Here is the PWM code for beaglebone:
https://svnweb.freebsd.org/base/head/sys/arm/ti/am335x/am335x_ehrpwm.c?view=markup

At some point I think I will expose PWM settings via gpioctl (and
possibly add a gpiopwm for a software based pwm).

Regards,
Luiz