real/simulated light sleep does not add up | adafruit | Page 1

white kraken Feb 4, 2026, 6:24 AM

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To start getting complicated. One measurement was made with the USB connected when powered on. The other measurement was USB unconnected, then powered on.

gilded raptor Feb 4, 2026, 4:20 PM

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what were the two measurements

white kraken Feb 4, 2026, 9:50 PM

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18.5mA with USB cable, 17.8mA without.

gilded raptor Feb 4, 2026, 9:52 PM

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I haven't tested an RP2040 feather, but on a Pico, when it goes to Deep Sleep, current drops down to 1-2 milliamps.

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(The RP2040 isn't great in low power modes)

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What's the CP code you're using?

white kraken Feb 4, 2026, 11:23 PM

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main.py:

import alarm
import board
import time
import microcontroller
import digitalio

pin_led = digitalio.DigitalInOut(board.LED)
pin_led.switch_to_output()
pin_alarm_button = alarm.pin.PinAlarm(pin = board.BUTTON, value = False, pull = True)

time.sleep(1)
for p in range(10):
    pin_led.value = 1
    time.sleep(0.2)
    pin_led.value = 0
    time.sleep(0.1)
alarm.light_sleep_until_alarms(pin_alarm_button)
# Avoid resetting into bootloader
time.sleep(3)
microcontroller.reset()

gilded raptor Feb 4, 2026, 11:26 PM

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oh. I've never used one of the light sleep modes. I'm not surprised the current saving is modest, especially on the RP2040

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I would not be surprised if the entire IO system had to stay active to detect a pin change.

white kraken Feb 5, 2026, 3:51 AM

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I did just test deep sleep with the same code, for which CPy helpfully writes 'Pretending to deep sleep until alarm, CTRL-C or file write.' with USB connected. And does drop down to practically 0mA. I can try to fix that another time.

#real/simulated light sleep does not add up