Power modes

The Pandora's battery

Power Modes

Without switching the device entirely off, it may be placed into low power mode or regular power mode; simply pressing the power button will toggle modes. Note that as of hotfix3, opening the lid in low power mode has no effect.

Normal Mode

This is the normal operating mode, display on, WiFi and Bluetooth on if requested. CPU speed can be selected by the user, and has a small impact on battery life. Screen brightness will also have a significant effect on battery life. The CPU should automatically self-regulate to the current task, and 10-20 hours battery life is possible depending on usage. This is mostly independent of the set CPU speed for any given task. At any time, the battery gauge will show the remaining battery life if the usage remains the same as over the past some seconds. See [1] for a detailed breakdown of power consumption.

Lid Closed

The only change with the lid closed is to turn off the LCD backlight and the display itself. This improves battery life, allowing music playback and streaming to continue. As of Hotfix2, the screen remains on if the device is powered up with the lid closed. It is also possible to set xfce to blank the screen after a period of inactivity, which helps with battery.

Low Power

Low power mode is toggled by a short press of the power switch to the right. The screen is off, the radios are disabled, the CPU max speed is set to 14 MHz. The device is still silently on, allowing for alarms to go off or it to be turned on again instantly. The power LED will be dimmed, and may appear to be off if you are outside in the sunshine.

Low power mode is probably going to be used as the normal "off" for most people, with true off (device powered down entirely, unable to respond to alarms or wake up quickly) available to conserve battery power. Turning the Pandora off completely is the best option if you don't plan on using it for few days or longer.

Since the Pandora has to be powered whilst it is charging, low power mode is best for fastest charging, and will even allow a full charge to be achieved from USB. It is also the best way to use the Pandora as a USB charger for other devices.

Opening the screen whilst in low power mode has no effect (screen stays off, clocks stay low), and you will need to use the power switch to resume.

At the moment, there is no clear advantage in slowing the clocks (other than being an effective pause button when playing MP3). The only saving is through disabling the radios. This is likely to be improved in due course since there are features in the omap processor for power saving which are being added to the linux kernel.

Power Off

Select Logout then Shutdown from the window manager to power off. If a charger is connected, the device will re-boot immediately. It is possible to get into a state where you believe it is powered off, but in fact it is using power at the normal screen off rate - so after 12 hours, 50% of your battery is gone. The Power green LED ought to be a tell-tale. It is possible that some bugs exist in this area, but nothing has been clearly identified[2]

A common problem seems to be that if you switch off before unplugging, your Pandora will re-boot even though it is now left unplugged. This problem is compounded by the low battery shutdown script being called repeatedly (and actually preventing shutdown).

To do a hard-reset of the Pandora (in case of software crashes), press and hold the Pandora key and flick the power button to the right.

To do a hard-shutdown of the Pandora, press and hold the Pandora key with right shoulder button held and flick the power button to the right, and then select shutdown from the menu.[3]

Events

The events which control power can be customised [4]. Lid switch, Power Switch, battery threshold and Window Manager shutdown commands. Note that the battery manager in xfce will also take action when the battery is low, by default forcing a shutdown at 5% (so you may observe a full boot process, the window manager appears, then immediately shuts down)

Charging

UK charger and adapter

It is possible to charge from the mains charger (use the supplied one or a GENUINE PSP adaptor only) or USB cable. While a charger is connected, remaining battery level is displayed, but the time displays 00:00. If charging from USB, it is possible that the battery will still discharge slowly, since the Pandora takes more current (in normal mode) than the USB can supply. Mains charge is configured to draw 1000mA, USB charge is more like 600mA.

It is not possible to charge the Pandora without turning it on - connecting the mains charger or the USB cable will turn it on automatically. The normal charging circuits rely on the CPU for configuration. In practice, this has minimal impact on usage, except that after charging, you might wish to unplug the charger and explicitly turn off if you don't intend to use the Pandora soon.

Full discharge charging: The pandora will shutdown in case of low battery power. However there is a protection circuit in the battery itself which will cut off the power output of the battery. The battery and the pandora seems to be dead in this condition, but it's not. If you plug in the power you'll see nothing happen - but the battery will be recharged very slowly until the battery is above it's cutoff level. This could take up to 30 minutes. Then the pandora will startup and the normal CPU controlled faster charging will continue. [5]

If your Pandora's battery is at less than 1% (actually configurable in XFCE), then you may have problems in using USB to charge the Pandora. Currently, USB is not recognised by the XFCE battery monitor so it will shutdown with no warning. As a workaround, you can put your Pandora into low power mode as soon as the flashing mouse icon (XFCE startup) appears. This should significantly delay loading the battery monitor widget, and even if the charge hasn't passed 1% by the time it checks, on the next try you should be there.

Operating Point

The OPP is a TI term which reflects the fact that low clock speeds can be achieved with lower supply voltage than the higher clock speeds. Increasing OPP will reduce the lifetime of the device significantly (from 10 years to 5 years of continuous use.) OPP3 is the default as shipped by OpenPandora.

Since at least SuperZaxxon 1.52, the system has shipped with a utility to modify the maximum OPP. It is part of the CPU-Settings app (found in your Settings menu). Select the option 'Set the max OPP level', select 'Change Setting' and read the following warning. Agreeing to it will allow you to set the maximum OPP in the range 3-5.

As of Hotfix4, it is possible to set a maximum OPP in the range 1-5 (for example, to 5):

echo 5 | sudo tee -a /proc/pandora/cpu_opp_max

This will then increase OPP to suit the requested CPU max, as pre-determined by a table built in to the kernel. These thresholds use OPP1 for below 125 MHz, and OPP5 for above 720 MHz . It is possible to set the limiter and maybe run at 500 MHz in OPP2 (depending on your specific chip). See this forum thread for actual results.

Times

• This data originates from different studies performed under different OS versions and use cases.
• Please add the source and a short note about the conditions you used, and if necessary more detailed ones to the Talk page. You can use Pandora System Info to monitor power consumption.

Mode	Time	Details, Source
Active applications/games	8-18 hours	SZ 1.52
Low load, low backlight brightness	20-25 hours	SZ 1.52
Drain the battery as fast as possible	4 hours	SZ 1.52, backlight at max brightness, constant wifi activity (big download), CPU stress test running at OPP5 and overclocking above 900 MHz, copying huge files from one SD card to the other, USB host and bluetooth activated (but nothing connected)
MP3 play, screen off	43 hours	MP3 playback in Audacious in OS SuperZaxxon, Beta 2, Kernel 3.2.1
Low Power Mode	30-75 hours	OS SuperZaxxon, Beta 2, Kernel 3.2.1
Power off	5% charge loss per week	although there are reports of much faster drain?[6]
Standby Mode (no longer applicable?)	160-200 hours	OS SuperZaxxon, Beta 2, Kernel 3.2.1
Mains charge, lid closed	4 hours	SuperZaxxon 1.52
USB Charge, operating	20 hours	inactive, screen+wifi on, may charge or discharge depending on load
USB Charge, low power	20 hours	estimate

Battery Calibration

• Fully charge to 100%, turn off the Pandora and leave it for 5 hours.
• A full charge is when, while charging,"cat /sys/class/power_supply/bq27500-0/voltage_now" reads around 4200000 and "cat /sys/class/power_supply/bq27500-0/current_now" reads around 800000. If the meter reads 100%, make sure to check these two files to ensure it's actually FULL. Realistically a charge current below 100000 is close enough.
• Then fully discharge (make sure that "cat /sys/class/power_supply/bq27500-0/voltage_now" returns about 300000), turn it off again for 5 hours.
• That's the process for recalibrating the fuel gauge.

Battery Care

• You can charge your battery to full charge, the charging circuits will then reduce the current to avoid overheating
• If you won't use the battery for more than a week, it is best to leave it at about 40% charged (as opposed to full)
• Don't worry about running it down too low, there are protection circuits to avoid a damagingly low discharge.
  • Avoid leaving the battery completely discharged though. When the power runs out, the system will be unable to shutdown cleanly, and might corrupt your files or the system.
• No harm will come if you only partially recharge it. If you've only got 10 free minutes to charge before leaving, go ahead. You'll put an hour of usage back into the battery, and you can always charge it more later.
• For best accuracy, the battery meter relies on watching the battery discharge over most of it's range (down to say 10%).
  • This will only affect the 'time to run' indication
• If you're not going to be using your battery for a very long time, the extremely best thing you can do for it is to discharge to 40%, seal it in an airtight bag, and put it in the fridge. Even years later, you pull it out, and it will be almost as good as when you put it in.

My Pandora does not start, even with the mains adapter plugged in

When a battery is inserted, the power goes into the battery, charges it and the battery powers the Pandora. When no battery is inserted, the power goes through the charging circuit directly into the Pandora.

What this means is, if the battery is really empty, the Pandora won't power on when connected to AC until the battery reaches a certain voltage level. Let it charge the battery (it could take 10 or more minutes before it starts to charge) or remove the battery and plug in the mains adaptor, it then should start.

Controlling LEDs and backlight

LEDs_and_backlight

Data provided by battery and power driver

Information from the battery and power supply in the pandora when it is booted. It lists readout data that is provided so that you for example can write your own applet showing current power status or include some power information in your application.

Power information is available via sysfs. This is the dmesg information about the battery:

bq27x00-battery 3-0055: support ver. 1.1.0 enabled

Fuel Gauge

/sys/class/power_supply/bq27500-0 reports how long the battery will run for.

Here is a list of the provided information and how to interpret the values:

node	meaning	interpretation
capacity	remaining capacity in %	100=full, 0=empty
current_now	discharging/loading rate	µA; negative: discharging; positive: loading
present	is a battery inserted?	1=yes; 0=no
status	Discharging/Charging
temp	monitoring IC temperature	decidegree celsius, value of 250 = 25.0°C
time_to_empty_avg	battery time left based on drain on some average; not used in XFCE applet	seconds; only relevant/existing when discharging!
time_to_empty_now	time left based on current drain; used in the XFCE applet	seconds; only relevant/existing when discharging!
time_to_full_now	time left for charging with the current usage; not used in XFCE applet	seconds; only relevant/existing when charging!
type	should always read "Battery" since it is a battery...
uevent	empty
voltage_now	current voltage left	µV

Power Management IC

/sys/class/power_supply/twl4030_bci_battery/ Manages charging, from the mains charger or from USB.

• online
  • 0 = No charger
  • 2 = Mains charger
  • 3 = USB charge

The mains charger takes precedence if USB and mains charger are plugged in. Pandora seems not to take power from both inputs for charging. Charging by USB only works with a powered system. If the system is off or the battery is empty, it is not possible to boot the system only by USB power (only tested on one Pandora, please recheck).

Please do keep in mind that all time values are plain estimates and can be "jumpy" depending on current system load, display brightness, WiFi/Bluetooth activity and things like the phase of the moon.

Battery monitoring

Various parameters readable from /sys/class/power_supply/bq27500-0/ , see this page.

Charging

/sys/class/power_supply/twl4030_*/*. Enable/disable charging through those files. The charger chip has trouble operating in automatic mode (overcharges the battery), so pndevmapperd uses enable/disable to prevent that.

config

/etc/pandora/conf/eventmap