Since the Phidget device is a USB device, it can only send a data packet every 8ms due to USB specifications. If the sample time is changed to below 8ms, to 2ms for example, you would get four samples every 8ms. This is not a limitation of the processor, since it is actually sampling every 2ms but can only send the data to the PC every 8ms. Additionally as you mention, the delay can also be from the long chain. Could you program a simple example that just lights the LED when the touch sensor is pushed in another programming language for comparison?
The 1129 is a capacitive touch sensor. The capacitance can change depending on the surroundings, and not necessarily if something is touching the sensor. This allows it to be triggered through objects like wood, glass and lexan. As you mentioned, the 1129 can only read a 0 or 999 - it only detects whether there is something there or not. It is not possible to detect size or distance.
Some possible solutions:
- Increase the thickness of the lexan.
- Decrease the size of the wire mesh, or replacing the mesh with the end of a wire.
Both of these solutions could also result in the notes never being sensed however, and could require a lot of trial and error for reliability and repeatability.
Instead of using capacitive touch sensors, you could look into resistive touch sensors, such as the 1131, or the 3103 and 3104 Force Sensing Resistors (FSR). I don't think that this would fix the delays, but you would be able to get a reading for how hard the sensor is pushed and do some volume related things.