CL1B power distribution

Richard A. Smith richard at laptop.org
Sat Apr 25 09:51:39 EDT 2009


>>> Additional changes from Gen 1 include the ability to both measure
>>> DC input current and VIN voltage, as well as EC control over the
>>> current drawn from the DC input. The intent was to better support
>>> charging directly from solar panels.
>> I hope that this will be available to activities like Measure.
> 
> Interesting point.  That would require extending the EC API, as they  
> go to an A/D
> not directly addressable by the main processor.
> 
>> Ideally updates could be frequent enough to pick up a waveform
>> from an unrectified power supply. (spare audio channel?)

Don't have much in the way of EC cycles available.  Don't have much EC 
ram left to cache values either.

I can make the readings available via EC commands but each command takes 
a few ms to complete and back to back commands will have a few ms of 
delay as well.  I'm guessing you might be able to get a 20ms update rate.

The best method would be to leave indexed IO enable and tell the EC to 
quit reading from the ports.  Then you could use indexed IO to read the 
AD registers directly.  I'm not sure what update speed you can get that 
way but it should be pretty fast.

-- 
Richard Smith  <richard at laptop.org>
One Laptop Per Child


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