NFC powered synth businesscard

So i build up the POC ... wrote a small firmware and .... IT WORKS .... well sort of. The circuit, unoptimized, needs around 3-4mA which drains the caps way too fast. However the touch sensors work flawlessly ... the I2C split was not problem and they are pretty much plug and play ..... nice.

I was a bit down BUT i noticed, holding a keycard in between makes my phone to keep the filed up .... and oh boy suddenly we have SO MUCH MORE POWER ... way more power than we need. I even was able to charge a 7F Supercap with no problems .... kinda insane.

Also ... KNOWLEDGE ACQUIRED

So the touch IC work without problem ... thats good so we can play around with the design like crazy. For the Energy harvesting im planning to trick around a bit .... since we need a tag to keep the field up, i will try to implement a 2nd antenna with the same IC i used on the Jolly-Tagger ... i tried it and this one also keeps the field up ..... this is gonna be good

So to actually test my idea i built a small prototype ..... some big ass 0805 caps, a rectifier, and attiny and two AT42QT1070.

Im not 100% sure on how to design the touch pads so i made every possibility. Grounded, meshed, with shiled ... and everything between just to see how the IC will react. I added a UART output just in case for possible debugging/experimantal purposes.

And yes .... the IC has a not-changable address so i split up the I2C into two. Having one on the main pinout and the other on the alternative pins.
Will it work? I have NO idea.

So before i do anything a found an old NFC antenna around. Measuring the inductance, getting a capacitor to make it resonant and added a full bridge rectifier to charge a capacitor bank.

The outcome ... well just by polling alone i was able to make the LED glimmer....

According to my calculations im able to get a "constant" ~1mA@2,5V .... kinda impressive .... lets see where it takes us.