thrillscience
Posts: 2
Joined: Fri Jan 04, 2013 6:18 pm

Sleep Mode / Wake from Sleep

Fri Jan 04, 2013 6:26 pm

Does the Rev B. Raspberry Pi have a low-power sleep mode, and a way of signaling to wake it from sleep?

I have an application in mind where I'd like to power it from batteries all day, and it doesn't need to be continuously running.

thinkmassive
Posts: 1
Joined: Wed Feb 10, 2016 1:17 am

Re: Sleep Mode / Wake from Sleep

Wed Feb 10, 2016 1:31 am

Since the Pi lacks a sleep/suspend state, the best you can do is halt the system (full shutdown) when work is complete, and send a reset signal on header P6 to wake it when needed. There's at least one commercial device that provides a capability like this.

To conserve power, make sure to disable unused peripherals (search for 'power' in the BCM2835 datasheet).

For very low power requirements you may want to migrate to a simpler microcontroller or more featured embedded computer (with a true sleep state), depending on your application.

fanoush
Posts: 544
Joined: Mon Feb 27, 2012 2:37 pm

Re: Sleep Mode / Wake from Sleep

Wed Feb 10, 2016 8:03 am

The software support is definitely not there and as it looks even the hardware lacks it or is tricky. Looks like the 'sudo poweroff' state is the lowest power state it can do except holding it permanently in reset which most probably cannot retain data in RAM properly

see also this issue
https://github.com/raspberrypi/linux/issues/1281
and some measurings for B model here
viewtopic.php?f=63&t=73983

unfortunately it looks like it is low priority for the RPi foundation and without more detailed datasheets and/or open source boot loader (mentioned e.g. here https://www.raspberrypi.org/blog/a-birt ... ent-493935 ) it is quite hard to do it by the community (if it is possible with current boards at all)

User avatar
rpdom
Posts: 17166
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Sleep Mode / Wake from Sleep

Wed Feb 10, 2016 8:11 am

Depending on how long it is required for each day, the capacity of your batteries, and the standby current of the Pi, it might be easier to disconnect the power when it isn't needed and power it up when required. A FET on the power line may be enough to control it, depending on the voltage drop, or even a small relay which may take 30-50mA when powered, but nothing at all when off.

You'd still need an external circuit to "wake" it up, whichever method you use.

mosespi
Posts: 508
Joined: Mon May 12, 2014 3:35 pm
Location: 34,-118
Contact: Website

Re: Sleep Mode / Wake from Sleep

Mon Feb 15, 2016 3:08 am

You need to throw some hardware at it for what most people consider an 'off' computer. There is no hardware on the Pi for this.. likely because most people will power the Pi from mains and are fine leaving the Pi on all the time. There is the cost factor as well, however minimal it may be.

I developed a UPS that can power down and more importantly power back up the Pi at set intervals. If for example you only need your Pi to snap a picture every 15 minutes for a webcam, this will save loads of power if you are running from limited battery or solar.

http://www.allspectrum.com/mopower/

Check the "UPS Timer Control Settings" on page 15 of the PDF, works like cron.
It does a fair bit of other things too.

You can roll your own on/off circuit too. Either microcontroller based or analog. It's all possible, depends if you want to spend more time and build your own or more money and buy something.

Regards,
-Moses
Power problems? MoPower UPS for the Pi
http://www.allspectrum.com/mopower/

Return to “Advanced users”