[OLPC New Zealand] [Testing] Testing Summary, Auckland 14 July 2012

[James Cameron]

Thanks for testing.

On Sun, Jul 15, 2012 at 11:27:11PM +1200, Tom Parker wrote:
> Jacob:
> Measure with resistance sensor, we find that the trace drops off the
> bottom of the screen at 6k??. It seems that the gain slider is a
> position control, not a gain control as in audio mode, this
> doesn???t seem to be explained in the documentation on wiki.sl.o.
> The position control can be used to position zero on the screen.
> 
> Shorting the input yields -10?? which is a little surprising as
> negative resistors are rare beasties.

The zero voltage point of the input channel won't always be zero in
the digital data.  This is specified in the datasheets for the chips.
Measure would need to learn the offset, with some sort of calibration
button.  This has always been the case, but the offset varies across
laptops.  You might find other laptops have other offsets; displaying
something other than -10.

p.s. Jacob is not in
http://wiki.laptop.org/go/OLPC_New_Zealand/XO_inventory

-- 
James Cameron
http://quozl.linux.org.au/