stm32: add machine.Timer implemented as a 1ms resolution soft timer #5254
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Would address #2693 |
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This commit adds an implementation of a "software timer" with a 1ms resolution, using SysTick. It allows unlimited number of concurrent timers (limited only by memory needed for each timer entry). They can be one-shot or periodic, and associated with a Python callback. There is a very small overhead added to the SysTick IRQ, which could be further optimised in the future, eg by patching SysTick_Handler code dynamically.
This commit adds an implementation of machine.Timer backed by the soft
timer mechanism. It allows an arbitrary number of timers with 1ms
resolution, with an associated Python callback. The Python-level API
matches existing ports that have a soft timer, and is used as:
from machine import Timer
t = Timer(freq=10, callback=lambda t:print(t))
...
t = Timer(mode=Timer.ONE_SHOT, period=2000, callback=lambda t:print(t))
...
t.deinit()
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This PR adds a very simple but useful implementation of
machine.Timerto the stm32 port, providing a "software timer" with a 1ms resolution, allowing unlimited number of concurrent timers. They can be one-shot or periodic, have a Python callback, and can be cancelled.It uses SysTick to implement the soft timer, so doesn't impact an existing hardware timer. There is a very small overhead added to the SysTick IRQ, which could be further optimised (eg by patching systick_irq code dynamically).
The Python-level API is intended to match esp8266 and esp32, like this:
Ultimately the Timer API will be refined further, see discussion at #2971, but for now this at least provides a starting point and something useful and portable.