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Comment by moffkalast | Hacker News Reader

True, I've gotten Pi 4s pretty low (< 1W), disabling the LEDs, Ethernet, HDMI, and USB controller, but it's never gonna equal a proper suspend.

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1W is honestly not that great, though. A smartphone will do 10x that out of the box, and still pling for Facebook notifications.

A smartphone has two entirely separate computers in it, the one that runs Android or iOS, and the baseband controller. The latter is built to be very power-efficient while waiting for a radio signal. It will wake up the dormant application OS computer when a push notification comes in.

The same likely can be built on top of an RPi, using, say, wake-on-LAN signaling, or some GPIO as an interrupt source. You'll have to suspend your OS while idle for a prolonged time though.

How did you disable the LED? I mean I can disable LEDs via /proc but not in config.txt correct?

Add

    # Disable Power LED after boot
    dtparam=pwr_led_activelow=off
    # Disable SD card activity led
    dtparam=act_led_trigger=none
    dtparam=act_led_activelow=off
    # Disable the ethernet LEDs - these are Pi4 specific values.
    # Look in the docs for the values for other Pi boards.
    dtparam=eth_led0=4
    dtparam=eth_led1=4

to /boot/config.txt

Thank you!

It appears to depend on firmware or kernel but for recent kernels (recent 6.1 or 6.2) activelow is no longer necessary [1]. It seems to work on CM4.

PS: my bad I disabled the LEDs via /sys not /proc previously:

> # for i in /sys/class/leds/*; do echo 0 > "$i/brightness"; done

[1] https://github.com/raspberrypi/firmware/issues/1742

I've had this drive me crazy.

The required lines were different between the Pi 2 and Pi 4 I was using at the time, and the documentation was not updated (or I'd found old docs).

An exercise in trial and error.

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