Open source STM32-based 13MHz+125kHz 192kB NFC+RFID implant
I accidentally found myself developing it. Ordered a couple of STM32L082KZU6 (5x5x0.5mm general purpose low power microcontroller chip), some 0.1mm copper wire for the antenna and 0.5mm wire for electrodes for shocking myself as a mean of feedback (and maybe reading some biopotentials; no idea if i can really detect something like nearby muscular contractions with such a simple circuit).
The STM32 has 192kB flash estate, hardware AES, ADC and temperature sensor, so i hope it to be an universal RFID "keychain" and maybe even an instant body temperature measurement device. First of all, i'll make a radio bootloader so i can reflash the device when it's in.
I'm not yet sure on the final coating of the device, now i'm considering grabbing a random tin-catalyzed silicone compound from a soap makers' shop. I will publish all the source code so the community would be able to avoid potentially insecure proprietary RFID chips and extend it (for instance, a photodiode or accelerometer could be added as a secondary data input and a supercapacitor could be added for data gathering between recharges (the chip itself can idle at 0.3µA)).
I'm aiming for a 30x10x1mm total size with a semi-flexible coil. A little drawing:
I wonder if there's more functionality i could add to the device w/o increasing its size.