Rockbox

  • Status Closed
  • Percent Complete
    100%
  • Task Type Patches
  • Category Battery/Charging
  • Assigned To No-one
  • Operating System iPod 5G
  • Severity Low
  • Priority Very Low
  • Reported Version Daily build (which?)
  • Due in Version Undecided
  • Due Date Undecided
  • Votes
  • Private
Attached to Project: Rockbox
Opened by dreamlayers - 2008-12-30
Last edited by torne - 2009-11-03

FS#9728 - Battery current measuring on the Video iPod

This patch allows battery current to be viewed at the debug screen. It adds another channel in firmware/target/arm/ipod/adc-ipod-pcf.c. In “View I/O ports”, the raw value is displayed as 4066_ISTAT. In the “Power status” screen of “View battery” the value scaled to milliamps and power in milliwatts is displayed. The current is flowing into the battery when charging and out of the battery when discharging. When external power is supplied and the battery is charged, current is zero.

Note that current is dependent on battery voltage, because at lower voltages the DC-DC converters need more input current for the same output power. That’s why I chose to also display power (based on Vbat * Ibat). That may still be slightly wrong if Vbat changed between readings, and DC-DC converter efficiency may change as voltage changes. It’s probably best to compare current on the same device at the same Vbat.

These values are also displayed in the iPod diagnostic, in Power → A2DTests → ChargingADC. I did not verify the accuracy of the scale factor; I just use the same one. The name 4066_ISTAT implies that this reading comes from the ISTAT pin of the LTC4066 chip.

Closed by  torne
2009-11-03 20:35
Reason for closing:  Fixed
Additional comments about closing:  

Committed in r23500

Here are some measurements comparing Firewire input power and Ibat. I’m using my 30 GB 5th generation iPod an an Apple A1070 wall charger which outputs 12.8 V with no load. The result is nice and linear. The only unexpected thing is the difference in slope between charging and discharging, because the ISTAT graphs in the LTC4066 datasheet are more symmetrical.

Semi-related things:
* Pitch of edge connectors on ISA cards is close enough to firewire 6 pin connector pitch.
* My iPod cannot charge via USB, probably because that part of the LTC4066 is damaged
* I used PDF because I can export graphs from Excel that way, and the data is hosted here, not at Google
* These graphs also illustrate current savings from clearing the LCD, putting the LCD to sleep and shutting down the BCM.

torne commented on 2009-07-23 16:25

Is there any reason not to commit this? dreamlayers’ measurements seem to show the scaling factor is right (which you would hope anyway since it was from the diagmode rom), and it’s handy reference information…

Updated patch to compile against latest changes in debug_menu.c
Also removed some tabs.

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