Capacitive touch buttons?

Rayman

Has anybody tried to do capacitive touch with P2 yet?
Seems like should be able to do better than with P1, like with Quickstart...

Maybe could Charlieplex up an array of buttons?

jmg

IIRC Chip did some examples using lowest current drive mode in self-feedback to generate triangular waveform.
That is then very capacitive dependent, and the frequency change can show a touch down to fF levels .
I'm not sure if Charlieplex can work with cap touch sense ?

Rayman

Did this use two pins or just one?

jmg

@Rayman said:
Did this use two pins or just one?

I think Chip used Schmitt + Negative local feedback and 10 µA drive, for a single pin triangle,

Each smart I/O pin has the following functions:

• Logic, Schmitt, pin-to-pin-comparator, and 8-bit-level-comparator input modes
• Negative or positive local feedback, with or without clocking
• Separate drive modes for high and low output: logic / 1.5 k / 15 k / 150 k / 1 mA / 100 µA / 10 µA / float

Tubular

@jmg said:

@Rayman said:
Did this use two pins or just one?

I think Chip used Schmitt + Negative local feedback and 10 µA drive, for a single pin triangle,

Thats it, just a single pin. So you can have up to 64 of such touch sensors.