FrameOS
Power save feature request
Hi,
I just built a spectra 6 7-inch frame and frameOS is amazing!
To power both the pi and the display, I use a huge 10.000mAh lipo battery and a USB-C charging circuit. The most amazing thing is that the pi runs straight off the battery, which is somewhere between 3.6V and 4V. Just connect the battery to the pi's 5V input .. the pi's buck converter makes 3.3V out of it anyway, so no boost circuit is required and when I plug in the USB-C charging port It does not interrupt the pi. I know it's a bit off spec, but it works.
HOWEVER, to save a ton of battery - especially for low refresh displays it would be great to be able to send the pi to sleep in a power save state and wake it up through an interrupt, render a new image, display and go to power save mode again.
Would that be feasible?
keep up the great work, many thanks!
Hey @yellobello
That is a neat setup and a great question. I didn't know the Pi was that flexible when it came to input voltage.
Generally you'd either need a CPU that supports deep sleep with auto wakeup, or you'd power off the CPU and turn it back on at an interval.
What kind of Pi are we talking about here? A Zero W2 or something bigger like a Pi 5?
The Pi 5 supports a real time clock and should have better deep sleep states, but I haven't tested this.
If we're talking about something like the W2, then its CPU doesn't support deep sleep. It has no internal timer that could wake it up. You could program it such that it runs shutdown when it's finished with its work. Then another circuit (an ESP32 or something much simpler) zaps GPIO 3 (pin 5) at an interval. This will trigger the Pi to wake up and repeat the cycle. Crude, but it'll work.
All of this feels like overkill to me. An alternative would be to use a chip like the RV1106 (e.g. in the LuckFox Pico Zero), which (allegedly?) supports deeper sleep states. However I haven't tested any of that... yet. I actually have a bunch of RV1106 development boards around and was planning on trying to get FrameOS working on them. So I guess stay tuned for that... :).
