There is no reason to specialize this per chip as it is only ever used
for JavaScript. Not only that, it is causing confusion and is yet
another quirk to learn when porting the runtime to a new
microcontroller.
This commit improves the timers on various microcontrollers to better
deal with counter wraparound. The result is a reduction in RAM size of
around 12 bytes and a small effect (sometimes positive, sometimes
negative) on flash consumption. But perhaps more importantly: getting
the current time is now interrupt-safe (it previously could result in a
race condition) and the timer will now be correct when the timer isn't
retrieved for a long duration. Before this commit, a call to `time.Now`
more than 8 minutes after the previous call could result in an incorrect
time.
For more details, see:
https://www.eevblog.com/forum/microcontrollers/correct-timing-by-timer-overflow-count/msg749617/#msg749617
On some boards the FPU is already enabled on startup, probably as part
of the bootloader. On other chips it was enabled as part of the runtime
startup code. In all these cases, enabling the FPU is currently
unsupported: the automatic stack sizing of goroutines assumes that the
processor won't need to reserve space for FPU registers. Enabling the
FPU therefore can lead to a stack overflow.
This commit either removes the code that enables the FPU, or simply
disables it in startup code. A future change should fully enable the FPU
so that operations on float32 can be performed by the FPU instead of in
software, greatly speeding up such code.
This reduces current consumption from 500-1000µA to very low (<10µA)
current consumption. This change is important for battery powered
devices, especially devices that may be running for long periods of
time.
This commit refactors both determining the current time and sleeping for
a given time. It also improves precision for many chips.
* The nrf chips had a long-standing TODO comment about a slightly
inaccurate clock. This should now be fixed.
* The SAM D2x/D5x chips may have a slightly more accurate clock,
although probably within the error margin of the RTC. Also, by
working with RTC ticks and converting in the least number of places,
code size is often slightly reduced (usually just a few bytes, up to
around 1kB in some cases).
* I believe the HiFive1 rev B timer was slightly wrong (32768Hz vs
30517.6Hz). Because the datasheet says the clock runs at 32768Hz,
I've used the same conversion code here as in the nrf and sam cases.
* I couldn't test both stm32 timers, so I kept them as they currently
are. It may be possible to make them more efficient by using the
native tick frequency instead of using microseconds everywhere.
This is the kind that is used in Go (actually CGo) for exporting
functions. I think it's best to use //export instead of our custom
//go:export pragma, for consistency (they are equivalent in TinyGo).
Therefore I've updated all instances to the standard format (except for
two that are updated in https://github.com/tinygo-org/tinygo/pull/1024).
No smoke tests changed (when comparing the output hash), except for some
wasm tests that include DWARF debug info and tend to be flaky anyway.
This commit lets the compiler know about interrupts and allows
optimizations to be performed based on that: interrupts are eliminated
when they appear to be unused in a program. This is done with a new
pseudo-call (runtime/interrupt.New) that is treated specially by the
compiler.
* runtime/atsamd51: fix clock init code
The DPLL0 initialization should set LDRFRAC and LDR, not LDRFRAC twice.
Also explain what the magic numbers are doing.
Ayke van Laethem
sago35
deadprogram
Jaden Weiss
Infinoid