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Sansа Clip Zip - Improve battery life
Mihail Zenkov:
I measure current between player and battery and try tweak power consumption.
Current in mA (less is better):
You can convert current to hours:
battery capacity (mAh) / mA = hours
For example rockbox with patch consume 10.9 mA when play flac, battery capacity in Zip - 300mAh.
300 / 10.9 = 27.5 hours
In reality it would be less - battery capacity degraded over time.
Some interesting results:
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.
Link for binary build: http://forums.rockbox.org/index.php/topic,48368.0.htm
saratoga:
--- Quote from: Mihail Zenkov on September 27, 2014, 05:28:21 PM ---I measure current between player and battery and try tweak power consumption.
Current in mA (less is better):
--- End quote ---
Awesome thanks, no one has looked at power on the sandisk players in years. I knew more improvements were possible but haven't looked into them.
--- Quote from: Mihail Zenkov on September 27, 2014, 05:28:21 PM ---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 ;)
--- End quote ---
Yes, the sandisk firmware uses the official flac decoder, which is VERY slow. We used it too for a bit, but quickly switched to ffmpeg's much faster one, which was then heavily optimized. It can decode a file using less than 10 MHz of CPU.
--- Quote from: Mihail Zenkov on September 27, 2014, 05:28:21 PM ---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.
--- End quote ---
We did tests years ago of lower clock speeds (and also lower memory bus speeds), and found that they made relatively little difference. This is actually why no one has bothered to get CPU frequency scaling running, it was believed to only have a very small impact on battery life. These results are therefore very interesting.
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? Perhaps this will motivate enabling CPU frequency scaling.
--- Quote from: Mihail Zenkov on September 27, 2014, 05:28:21 PM ---rockbox-backlight.patch: disable DCDC15 when screen off (save 1mA), like we already do in Clip Plus. Good for inclusion in main branch.
--- End quote ---
I'll try this out and commit if it works ok for me.
--- Quote from: Mihail Zenkov on September 27, 2014, 05:28:21 PM ---rockbox-usb.patch: prevent USB power consumption (additional 5 mA in all modes) after it disconnected. Also good for inclusion in main branch.
--- End quote ---
These needs to be tested, but looks like a big oversight on our part. I suppose this may help with other AMS devices too.
--- Quote from: Mihail Zenkov on September 27, 2014, 05:28:21 PM ---I try many other clocks/voltages without any significant difference.
--- End quote ---
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.
saratoga:
http://gerrit.rockbox.org/r/#/c/988/
http://gerrit.rockbox.org/r/#/c/989/
Will commit in a day or two if no one sees any problems. 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.
saratoga:
Some comments about the voltage patch:
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.
saratoga:
Patch with work in progress frequency scaling: http://www.rockbox.org/tracker/task/11297
As 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.
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