App note: A method of enabling more touch pads With 5-ch CapTouch module on LPC804 MCU

App note from NXP demonstrating capacitive pin channels expansion on LPC804 MCU with SWM (switch matrix) and scan sequences. Link here (PDF)

The CapTouch module on LPC804 supports only 5 channels by hardware. Normally, the device with up to 5 channels can fulfill some simple use cases. But if more channels are required by the original CapTouch module, the LPC804 might not support the usage. Even by the LPC845, the CapTouch module support up to 9 channels.
However, the SWM module on LPC804 can remap the CapTouch function to almost all the GPIO pins, while the CapTouch feature was the fixed function for pins on LPC845. With suitable software and the settings to CapTouch, the LPC804 use the different pins at different time slice, then it can support more channels than the hardware limited count by software. For example, 12 channels of normal dialing keyboard, or more.

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