[sdiy] FPGA/Synth DIY thoughts

[harry]

Grant Richter wrote:

<snip>

> Nick Hartl and I have experimented with capacitive keyboards done with a
> single FPGA. Connect two pins together with a resisitor, and put a
> touchplate one one pin. Then toggle the drive pin and time how long it takes
> the other to change state. This measures the C in the RC time constant.
> Touchy about temperature and humidity though (no pun intended).
>

Couldn't you make some form of shielded capacitive switch as a reference and
somehow autocal the rest (to remove temperature / humidity) ?

I saw some capacitive touch switch ICs in a magazine recently... but with 30mS
response time and an autocal that runs like once a minute... I thought not....

H^) harry