Time / Delays — pymcu.time#

from pymcu.time import delay_ms, delay_us

Busy-wait delay functions calibrated to the target clock frequency. No hardware timer is consumed — delay loops use counted CPU instruction cycles.

delay_ms(ms: uint16)#

Busy-wait for approximately ms milliseconds.

  • ms may be a runtime variable (uint16).

  • Maximum: 65 535 ms (~65 seconds).

  • On AVR at 16 MHz: 21 outer × 255 inner × 3 cycles ≈ 1 ms per iteration.

delay_us(us: uint8)#

Busy-wait for approximately us microseconds.

  • us may be a runtime variable (uint8).

  • Maximum: 255 µs.

  • Accurate for us >= 4 on ATmega328P at 16 MHz.

Example#

from pymcu.time import delay_ms, delay_us
from pymcu.hal.gpio import Pin

def main():
    led = Pin("PB5", Pin.OUT)
    while True:
        led.high()
        delay_ms(500)
        led.low()
        delay_ms(500)

Notes#

  • Interrupts are not disabled during delay loops. An ISR executing during a delay will extend it by the ISR duration.

  • For precise, non-blocking timing, use hardware timer interrupts (@interrupt + Timer0/1/2).

  • delay_ms(0) returns immediately without spinning.

millis() and micros()#

For elapsed-time measurements, use millis() and micros():

from pymcu.time import millis, micros
from pymcu.types import uint32

start: uint32 = millis()

# ... do work ...

elapsed: uint32 = millis() - start

These use a Timer0 overflow ISR to maintain a 32-bit counter. They require Timer0 to be running with prescaler 64 (the default). The counter is read atomically under CLI/SEI.