Implement clock and pwm modes

[drahoslove]

Hi there.
I managed to add third pin mode - clock.

It is just clock (using CM_GPnDIV and CM_GPnCTL registers) - no pwm (yet).

Suggestions about better method/function naming are welcomed.
I tried to be consistent with current ideology, but not sure if it makes sense.

So this: PinMode(pin, rpio.Clock) <=> pin.Mode(rpio.Clock) <=> pin.Clock()
is analogical to: PinMode(pin, rpio.Output) <=> pin.Mode(rpio.Output) <=> pin.Output()

and this: SetFreq(pin, 10000) <=> pin.Freq(10000) <=> ???
is analogical to: WritePin(pin, rpio.High) <=> pin.Write(rpio.High) <=> pin.High()

Also not sure if it might make sense to add more public methods eg. for stopping/resetting clocks.

Please merge this if you like it.

[drahoslove]

So I also implemented simple pulse width modulation functionality.
For example, to set pin to 38kHz with 1/4 duty cycle you can do:

pin.Pwm()
pin.DutyCycle(1, 4)
pin.Freq(38000 * 4)

Dimming led example:

package main

import (
        "os"
        "time"
        "github.com/stianeikeland/go-rpio"
)

func main() {
        err := rpio.Open()
        if err != nil {
                os.Exit(1)
        }
        defer rpio.Close()

        pin := rpio.Pin(19)
        pin.Mode(rpio.Pwm)
        pin.Freq(60000)
        pin.DutyCycle(0, 32)

        for i := 0; i < 5; i++ {
                for i := uint32(0); i < 32; i++ { // increasing brightness
                        pin.DutyCycle(i, 32)
                        time.Sleep(time.Second/32)
                }
                for i := uint32(32); i != 0; i-- { // decreasing brightness
                        pin.DutyCycle(i, 32)
                        time.Sleep(time.Second/32)
                }
        }
}

[Albert221]

Can @stianeikeland merge this?

[drahoslove]

@stianeikeland, I know it's a lot of changes to review at once, I've done some refactoring even in your code and so on. But I would appreciate if you can check it and merge.

Or, if you do not want to maintain this repo anymore, then I would like to ask your permission to separate my fork from your repo and make my own stand-alone repository (with a different name perhaps and with mention, it is based on your work, of course.) which I will maintain by myself.

[stianeikeland]

Hey,
sorry for dropping the ball on this, I've been meaning to play with it but other things keep getting in the way.

Anyway, I've had a go at it this evening, and managed to make a LED phase in and out using an old Raspberry PI 1 on pin 18.

Code seems well written and works as intended, so I'll merge this as is.

Would love to have an example program (maybe like the one you have above) that demonstrate how to use PWM. Feel free to add that if you want :) (Or I can just grab your example from above, let me know) :)

EDIT: i copied your example program to the examples folder, feel free to change it if you want.

Thanks!

[drahoslove]

Great, thank you.
I think the example is ok. But I might change it just slightly - point out that result frequency of pin in PWM mode depends both on Freq and DutyCycle arguments - which may not seem obvious.

I noticed a tiny error in the code. Will make PR soon.

I would also consider adding a link to https://godoc.org/github.com/stianeikeland/go-rpio to readme - for people who do not know Golang so well and do not know this service exists, and just because it is convenient.