Implement pin interrupts

[aykevl]

This PR implements pin interrupts for Nordic devices and for SAM D21 devices.

I have kept the API very simple, so it is easy to generalize to many different microcontrollers. It is also possible to make it faster, but that would make the API also less flexible. Right now it will just read the callback from a global, which should be good enough for most purposes.

Something else that it doesn't implement (yet) is level interrupts (as opposed to edge interrupts). Level interrupts, while (probably) easier to implement in hardware, are harder to use in practice. The main advantage of level interrupts appears to be that some chips support them even in very low power states. For simplicity, I've just left them out in this version.

I have also implemented interrupts for AVR devices (Arduino Uno and Digispark), so that means 3 different chip families support this API. However, the code needs to be cleaned up a bit and I would like to clean up pin handling first (see #1093).

There are some features that I have not implemented, such as using one interrupt channel for multiple pins on the SAM D21. This would have complicated things so again, I've just left that out.

[deadprogram]

@aykevl merge conflict needs resolution, please.

[sago35]

@aykevl
I've started making an atsamd51 version
I still need to clean up the code, but it's working.
I'll push it later.

Here's something I noticed about SAMD21, so I'll report it.

1. Parentheses are required.

• Addr.Set((addr.Get() &^ 0xf << pos) | uint32(change)<<pos)

• addr.Set((addr.Get() &^ (0xf << pos)) | uint32(change)<<pos)

2. You need to OR multiple EICs to enable them.

• sam.EIC.INTENSET.Set(1 << extint)

• sam.EIC.INTENSET.SetBits(1 << extint)

Translated with www.DeepL.com/Translator (free version)

[aykevl]

@deadprogram rebased.

1. Parentheses are required.

• Addr.Set((addr.Get() &^ 0xf << pos) | uint32(change)<<pos)
• addr.Set((addr.Get() &^ (0xf << pos)) | uint32(change)<<pos)

Oops, thank you for catching that! I've updated the PR.

2. You need to OR multiple EICs to enable them.

• sam.EIC.INTENSET.Set(1 << extint)
• sam.EIC.INTENSET.SetBits(1 << extint)

I don't think so. INTENSET already performs the SetBits operation in hardware. The manual says:

Writing a zero to this bit has no effect.
Writing a one to this bit will set the External Interrupt x Enable bit, which enables the external interrupt.

[sago35]

1. You need to OR multiple EICs to enable them.

• sam.EIC.INTENSET.Set(1 << extint)
• sam.EIC.INTENSET.SetBits(1 << extint)

I don't think so. INTENSET already performs the SetBits operation in hardware. The manual says:

Writing a zero to this bit has no effect.
Writing a one to this bit will set the External Interrupt x Enable bit, which enables the external interrupt.

I made a mistake.
It certainly says so in the manual.

[sago35]

I wrote the code for SAMD51J19A.
I checked with feather-m4 and it seems to be working fine.
I haven't confirmed this with the SAMD51J20A yet.

https://github.com/sago35/tinygo/tree/interrupts-pins-samd51

I'm struggling with how to write the following parts.
Is there a better way to do it?

1. sam.EIC.CTRLA.Set(0) or sam.EIC.CTRLA.ClearBits(0x02)
   • https://github.com/sago35/tinygo/blob/interrupts-pins-samd51/src/machine/machine_atsamd51.go#L352
2. Is it better to define it outside of SetInterrupt()?
   • https://github.com/sago35/tinygo/blob/interrupts-pins-samd51/src/machine/machine_atsamd51.go#L384
3. I'd like to write a little nicer, but interrupt.New() only accepts const values, so this is how it's implemented.
   • https://github.com/sago35/tinygo/blob/interrupts-pins-samd51/src/machine/machine_atsamd51.go#L393
4. I want to make an example, but the feather-m4 I have doesn't have a button.
   Creating an example for pybadge is one thing, but since there is no machine.Button, the other examples need to be modified.

[aykevl]

@sago35 it would be easier to give feedback on an actual (work-in-progress) PR. Can you perhaps make one?

[sago35]

@sago35 it would be easier to give feedback on an actual (work-in-progress) PR. Can you perhaps make one?

I made #1111.

[deadprogram]

Excellent progress on this! Now merging.