Turtle Art sensor xo 1.75 range voltage

James Cameron quozl at laptop.org
Fri Jun 1 22:05:59 EDT 2012

Thanks for testing, this sounds interesting.

On Sat, Jun 02, 2012 at 11:24:45AM +1000, forster at ozonline.com.au wrote:
> > We should test the calibration again.
> Walter, Guzman
> Testing with TA140
> It looks like the 1.75 audio circuit was changed between the
> preproduction and the ramp unit 1.75's

I don't see any change.

> Testing on SKU199 and SKU204, the impedance has gone from 1k to 4k
> and the calibration is all wrong on 204

Possibility of damage?  How are you measuring this, so that I can
reproduce on units that I believe are undamaged?

Are you measuring DC impedance with laptop power off, or on?  With the
microphone bias off or on?  With the DC mode off or on?

If the kernel is running, are you measuring with the same kernel?

> (TA calibration should be OK for the moment on preproduction SKU199)
> Can laptop.org please confirm that there was an audio redesign
> between SKU199 and SKU204? Is the SKU204 design now stable or can we
> expect further changes? 

I can't confirm.

> Is the input protection the same as the 1.5: "The XO-1.5 is
> protected by a resistor,(1/16W 470 ohm SMD0402) and a pair of diodes
> to ground and to +3.3V which should protect -6V to +9V continuously,
> and up to higher voltages for shorter periods of time."
> http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Specifications

There are some differences against 1.5, in that there are two
channels, on the tip and ring of the connector respectively.  Please
make sure you are using a stereo plug with correct manufacturing
tolerances.  Test for shorting between the left and right channel pins
after the plug is inserted.

After the socket, there is a 470 ohm series resistor on each channel.

After that, reverse diodes to ground and +3.3.

After this protection, there is the microphone bias supply, DC mode
switch and the codec.  All these are under software control.

James Cameron

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