My Gta02s wont charge / chgena = 0 by default

Werner Almesberger werner at
Mon Jun 23 23:36:04 CEST 2008

Joerg Reisenweber wrote:
> Saturday Jan mentioned there allegedly is some exception for USB allowing a 
> spike up to 500mA for some ms, for init purposes.

That would be handy :-)

Here's what happens when we power up (three runs, all with the same

The red graph is the current we draw. Green is the voltage at the
cathode of one of the LEDs behind POWER. The u-boot you see here has
been instrumented to switch the LED on when start.S begins executing,
and to turn it off again when u-boot has loaded and relocated itself.

The time during which the LED is lit is the small step around 0.5V in
the green graph.

Unfortunately, the resolution in the time axis if very poor. What we
can see is that the current spike happens around the time u-boot does
its first timid steps and not a lot earlier (which would be nasty).

Note that this is a GTA02v5, so the POWER LEDs (I turn on both of them)
contribute about 100mA to all this. So the charger may actually kick in
even a bit later.

- Werner

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