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I measure current between player and battery and try tweak power consumption.Current in mA (less is better):
1. Original firmware have problem with flac (double power consumption).2. Themes can significantly differ in power consumption when screen on.3. Radio consumes too much (but I didn't try to optimize it).4. We have room to improve battery life
rockbox-improve_battery_life.patch: set master clock to 48 MHz, undervolting CVDD1, CVDD2, PVDD1. WARNING: this patch may cause instability, freeze or sound quality degradation.
rockbox-backlight.patch: disable DCDC15 when screen off (save 1mA), like we already do in Clip Plus. Good for inclusion in main branch.
rockbox-usb.patch: prevent USB power consumption (additional 5 mA in all modes) after it disconnected. Also good for inclusion in main branch.
I try many other clocks/voltages without any significant difference.
Do you know how much of the change is from the voltage settings and how much is from the CPU frequency?
Or is it that lower clock means you can more safely use a lower voltage?
We did a lot of testing years ago, I will try to find the results and forward them to you. I found that increasing PCLK (the memory bus is on this) greatly increased performance but also power draw. At lower speeds, the player was slower, but more efficient. Running the memory faster massively improved how fast some of the decoders were (far fewer MHz needed for realtime playback) but decreased battery anyway.
Note that I changed the backlight current sink on value to be 91 (its previous value) rather than 90. Probably doesn't matter but I was unclear on why it was changed.
1) Reducing the main CPU frequency is fine for FLAC and for people who don't use much DSP effects, but probably even mp3 + EQ would skip that low.
2) If you change any of the registers related to supply voltages, make sure that you don't reduce the device's maximum volume. 0dB should be the max without distortion if the audio hardware has the correct voltages.
Patch with work in progress frequency scaling: http://www.rockbox.org/tracker/task/11297As you can see we never figured out why dynamically scaling the frequency reduced battery life. Possibly this was a mistake or oversight if you found that lowering the clock improved battery life.
I think that is too low. The maximum is 60MHz, and we found acceptable performance down to about 20MHz (lowering it too much means the CPU wastes a lot of power waiting for memory loadds).
By the way, can you join use in #rockbox? We are discussing these patches.
Edit: Testing the USB and backlight changes increased my Zip runtime by 32%.
To help with testing, I've added new debug menus that show the current SOC voltage regulator outputs (using an on board A/D to read the voltages). You can see then under System -> debug -> view io ports and then hit the down button to scroll through all the voltages.
By the way one user testing the lower CPU clocks found that they break most formats other then flac. So if we want to lower them much frequency scaling will be needed.
Have you taken any measurements of AVDD17 or AVDD27? Looking at the voltages, we run AVDD17 a little higher because it determines the maximum headphone output. I was thinking raising it might be useful, but I won't do that if it uses a lot of power.
Edit: If I understand correctly, AVDD17 is the analog voltage used for almost everything but headphone amplifiers (line out, mixers, etc) while AVDD27 is the headphone output. I wonder if AVDD17 could be lowered since we do not use the line out.
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