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i want to use multiple capacitive touch keypads with arduino uno but number of IO ports are not enough. So I decided to use MSP23S17 port extender. Now i have to find some methods to sense the touch keypad without using its library. Can anyone tell me if there is any way to do the task.

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    Tricky at best. CapSense relies on pretty tight time measurement to determine small changes in capacitance. You would be better off using a proper CapSense interface chip. There's plenty to choose from - most of them I2C based. – Majenko Aug 22 '16 at 11:32
  • I am new in this field. Can you please refer me any CapSense interface chip. I am using the following touch keypad by waveshare Waveshare Touch Keypad – Danyal Aug 22 '16 at 17:03
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Here's one: Microchip mtch6102, though it might be a little more complex than you're looking for. All the others I found with a quick search were surface mount or single button controllers. You might be able to multiplex a single button controller like the Atmel AT42QT1011, but I don't know what the settling or reset times are. It may take to long to change pads, reset the chip, then wait for settling/calibration time (if any).

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