The `machine.Pin` type was a int8, which works fine but limits the
number of pin numbers to 127. This patch changes the type to uint8 and
changes NoPin to 0xff, which allows more pins to be used.
Some boards might not have that many pins but their internal
organization requires more pin numbers to be used (because it is
organized in pin ports and not all pins in a port have a physical
connection). Therefore the range of a int8 is too low to address these
higher pins.
This patch also has the surprising side effect of reducing binary size
in a number of cases. If there is a reduction it's usually just a few
bytes, with one outlier: the driver example amg88xx when compiled for
the pybadge board. I have not seen any increases in binary size.
Commit fc4857e98c (runtime: avoid recursion in printuint64 function)
caused a regression for AVR. I have tried locally with LLVM 11 (which
contains a number of codegen bugs) and the issue is no longer present,
so I'm assuming it's a codegen bug that is now fixed. However, LLVM 11
is not yet released so it seems best to me to work around this
temporarily (for the next few months).
This commit can easily be reverted when we start using LLVM 11.
This is necessary to avoid a circular dependency between the device/avr
and runtime/interrupts package in the next commit.
It may be worth replacing existing calls like device/arm.Asm to
device.Asm, to have a single place where these are defined.
Previously, chansend and chanrecv allocated a heap object before blocking on a channel.
This object was used to implement a linked list of goroutines blocked on the channel.
The chansend and chanrecv now instead accept a buffer to store this object in as an argument.
The compiler now creates a stack allocation for this object and passes it in.
There was what appears to be a race condition in the Tx function. While
it would work fine in many cases, when there were interrupts (such as
when using BLE), the function would just hang waiting for `EVENTS_READY`
to arrive.
I think what was happening was that the `spi.Bus.RXD.Get()` would start
the next transfer, which would complete (and generate an event) before
`EVENTS_READY` was reset to 0. The fix is easy: clear `EVENTS_READY`
before doing something that can trigger an event.
I believe I've seen this bug before on the PineTime but I couldn't find
the issue back then.
