Hi everyone,

I'm working on an IoT access control module using an ESP32 and the R503 fingerprint sensor. The built-in library is limited to 200 templates, but I need to support 1000+ users.

My plan is to use the R503 only as a reader. I want to capture the fingerprint, generate the character file (feature set), and use UpChar to pull those bytes to my database. When someone scans their finger, I’d pull the candidate templates from my DB, send them back to the sensor’s RAM using DownChar , and use the hardware Match command to verify.

Has anyone done this successfully? Specifically:

Is the UpChar data consistent enough for 1:1 matching after being stored externally for a long time?

Is there a way to use these proprietary bytes with some alternative? or am I locked into using the sensor hardware for the matching logic?

I want to avoid transferring full images via UART due to latency.…