[PATCH 1/1] uboot-pcf50633-default-curr-lim-1A.patch

Marko Mäkelä msmakela at gmail.com
Fri Feb 22 13:08:21 CET 2008

2008/2/22, Andy Green <andy at openmoko.com>:
> Well it is interesting but the charger thing is a done deal for us
> already and it is okay as far as it goes.  It would have been nicer to
> use this standard method, but if as Harald says if it turned up too late
> to use it, well its okay.

I understand. The specification is less than a year old, and it takes time
until it is implemented in widely used chipsets.

However, I hope you can consider adding a user-space interface for
specifying the charging current. Then I could violate the USB specification
and build a device that would charge the OpenMoko while it is in USB host
mode. The device would provide a USB HID interface to some sensors, such as
odometer (about 85 mm steps from the dynamo hub), cadence, and heart rate.
Then the OpenMoko would record all this information during the bicycle trip.

Failing that, I think I can afford to wait a couple of more years for the
next generation. By then I reckon there will be greater selection of GPL
navigation software as well.

> to load.  The nominal output current of the SON28 that I have in my bike
> > <http://www.nabendynamo.de> is 580 mA.  If the current limit in the
> Its a lot of power!  But this is just a matter of regulation before
> giving it to the device.

Right. The overvoltage protection consists of two 5-watt zener diodes before
the MOSFET rectifier bridge, and a low-dropout 5-volt regulator after the
rectification. I hope it will be sufficient, but I'll have to test it to be
sure. This protection will be needed when there is too little or no load
when the circuit is connected to the dynamo. For instance, old (3.5mm) Nokia
phones tend to interrupt the charging current at about 2 Hz rate. Without
any load after AC/DC rectification (testing with a salvaged wall-wart), I
measured up to 96 volts from the output capacitor. :-)

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