Re: Support for PWM on RPI3 GPIO

[Hal Murray <hmurray%megapathdsl.net@localhost>]

> Iâ??m tempted to just plan to use bcmpwm (and fix it up, obviously) to drive
> GPIO18  ...

That seems like a fine plan with the additional benefit that NetBSD gets a 
clean working bcmpwm driver.  I was tossing out an idea in case you hadn't 
thought of it and/or it was a better fit for what you were in the mood to do.

[serial port]
> RPI3 only has one, yes?

BCM2835-ARM-Peripherals.pdf says it has 1 and 1/2.  The other one is a "mini 
uart", just good enough for use as a console.

The main UART is mostly a 16C550.  I expect that it doesn't support a raw 
binary mode but I haven't worked with 16x50 chips for a long time.  I expect 
you can tune your transistor such that 1 out of 10 is a reasonable minimum 
brightness and 9 out of 10 is a reasonable max brightness.

There might be some other peripheral you can use as a low tech output only 
device.  The PCM/Audio comes to mind.  I didn't look deep enough to see if 
the serial out pin comes out or only goes to a D/A.

[We did something like this many years ago to drive an IR LED.  I forget the 
details.

-- 
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