Finally got my hands on the FPC1020 fingerprint scanners! These things are tiny, SPI-based, and perfect for a built-in solution. I built test boards, hooked them up to a NodeMCU, and wrote a basic Arduino sketch to read the hardware ID. Next step: integrating with the main authenticator project!
The PCBs finally arrived—couldn’t resist jumping straight into assembly. Hot air soldering the ESP32 Pico D4 was a first for me, but surprisingly satisfying! The prototype is up and running, even on battery power. Now the real challenge begins: fingerprint scanning and matching. Let’s gooo!
Tried to go full DIY and desoldered the fingerprint sensor from the R300 module… but hit a wall—the pad layout doesn’t match any docs I could find 😕. So, switching gears: I’ve designed my own custom dev board for the authenticator with ESP32 Pico D4, ATECC508A, and room for a scanner. Boards are on the way!
Using a button for FIDO2 user verification felt… a bit too easy to spoof. So I grabbed two fingerprint modules—GROW R300 and FPC1020—to try adding real biometric authentication. R300 might even let me skip its built-in MCU and handle image processing myself. Let’s see where this goes!
After getting FIDO2 working on Android, I gave it a go on the ESP32. Started with Arduino, but switched to ESP-IDF for more control. It’s super stripped-down—only one in-memory credential and a button for user presence—but it works! Got both registration and login running. Video inside!
Slightly tired of big and long-running projects both at work and at home I decided to make a small spin-off project to help me working with ESP8266/ESP32 devices. Is there any reason to make it when there are a lot of cheap USB-Serial converters in the market? I don’t think so. My only reason to make it is to have cool addition allowing ESP8266s to be programmed automatically without flash/reset buttons but simple circuit with two transistors. Most of the USB to Serial converters simply do not have this circuitry on board. And, of course, I wanted to have some fun.
Spent a couple weekends deep-diving into a real FIDO2/WebAuthn implementation—and wow, it’s more complex than it looks. Ended up rebuilding the BLE GATT server on Android for better control. Got “Make Credential” working (video inside!), plus found a quirky Chrome spec mismatch along the way.
Got into a Reddit convo about showing JPEGs on e-ink displays with ESP8266—and turns out, you don’t need an external service to dither images. Just a bit of code magic in C++ or Python can convert JPEGs to black and white right on the device. Simple and fun!