[Gta04-owner] Current consumption during suspend

Dr. H. Nikolaus Schaller hns at goldelico.com
Sat Aug 25 19:29:09 CEST 2012

Am 25.08.2012 um 18:21 schrieb Christoph Mair:

> On Sat, Aug 25, 2012 at 3:47 PM, Christoph Mair
> <christoph.mair at gmail.com> wrote:
>> - the current consumption has periodic spikes with intervals of 500ms
>> and 1.42s
> These spikes [1] disappear if the modem is registered to the network
> with a valid sim card. Now I could observe small spikes occurring
> every 30 seconds.
> Further observations: If the sleep current is not somewhere around
> 20mA but near 25mA the ITG-3200 may caused the additional power
> consumption. There seem to be a few cases where the chip isn't reset

I know one case where it happens for sure: if you connect USB power
without battery, the device will not visibly boot. Rather it will try to boot,
but shuts down after some 100-500 ms. This makes the ITG state machine
run into "no-response" mode. Even if you insert the battery later and the
device finally boots.

If you put in the battery first and the USB power next, it will properly

> correctly which causes its I2C interface to malfunction and therefore

I2C will timeout in this situation.

In this case it should be possible to shortly pulse off the VAUX that
powers the sensors. Although this makes the ITG being operated outside
of the spec shortly (VIO > VDD) it resets the chip. This is IMHO acceptable
since the VAUX LDO is current limited and is only a fallback for the rare
case that the ITG does no longer respond.

This could be hacked into the driver - although it makes it *very* specific
to the GTA04 boards and probably nobody else needs it in a ITG3200

@NeilBrown: is it possible that the ITG3200 can notify the board file
or some VAUX regulator just about the I2C timeout? So that generating
the emergency reset is clearly separated from the driver?

> the kernel can't tell it to suspend.
> I also removed the metal shield of my modem to get a thermal view of
> the inside. Result: no visible power leakage.
> Best regards,
>  Christoph
> [1] http://chonyota.net/gta04/infrared-2/currentconsumption.png



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