On Thursday I was able to get in to the electronics labs and test the connections of the Kaoss Pad. I used an oscilloscope to test the voltages of each of the six connections under a variety of conditions.
These conditions were:
- Hold button OFF without using the touch pad
- Hold button ON, X and Y on pad set to 1,1
- Hold button ON, X and Y on pad set to 9,1
- Hold button ON, X and Y on pad set to 1,9
- Hold button ON, X and Y on pad set to 9,9
- Hold button ON, X and Y on pad set to 5,5
- Hold button held down
- When touching the touch pad with hold button ON and OFF
Through this I learned that, as expected, a constant signal runs on every connection at all times. This is 6V peak-to-peak on all but one of the channels with a time period of 20ms. When the hold button is pressed down, the voltage is raised to 8V which causes the hold function to switch between the on and off states.
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| Standard waveform when XY pad is not touched. |
All of the recorded values shown below were taken at
the guitar end of the connection, though these were checked and found to
be the same as at the Kaoss pad end and so only one set was written down. This suggests that the serial cable has no noticeable effect on the signal.
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| Results page 1 |
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| Results page 2 |
It was also shown that when the touch pad is used, regularly spaced spikes appear in the waveform. They are approximately 0.2ms wide in total and about 2V high. Their shape is changed depending on the position of the finger on the pad. This variation controls the stored parameters of the KP unit.
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| Additional notes |
