Issues when setting bits in registers

[thejpster]

In pwm.rs I saw:

pad.gpio[self.pin].write(|w| w.ie().set_bit());
pad.gpio[self.pin].write(|w| w.od().clear_bit());

My understanding of write is that it does:

let w = register.defaults();
let w = closure(w);
register.set_bits(w);

So the second line (clearing od) will undo the effects of the first. This should probably be:

pad.gpio[self.pin].modify(|_r, w| {
    w.ie.set_bit();
    w.od.clear_bit();
    w
});

[thejpster]

The default value is 0x56 or 0b01010110 which is bits 1, 2, 4 and 6. This is equal to:

• OD = 0 = Output Enabled
• IE = 1 = Input Enabled
• DRIVE = 0b01 = 4mA
• PUE = 0 = Pull-Up Disabled
• PDE = 1 = Pull-Down Enabled
• SCHMITT = 1 = Schmitt Input Enabled
• SLEWFAST = 0 = Slow GPIO Mode

I think this means the two lines I highlighted above are at least /harmless/, as they reset the pin to defaults, and then change one specific bit to a value that it already has in the default.

[9names]

I mentioned this in matrix but didn't remember to make an issue for it.
There was another write/modify mixup caught in a review comment on the PWM rework PR, but it's good to have a reminder that it's not done yet.

[9names]

Fixed in #80