I had a similar problem on the ESP32. (If you really want a clean signal I think that you will need an external Schmitt trigger.) I solved it differently with a timer as follows: static uint32_t prevT = 0; void IRAM_ATTR IOhandleInterrupt() { uint32_t t = micros(); uint32_t dt = t -prevT; if (dt<150...

This is a summary of getting a PN532 to work on the UART to help other who might have the same problem. I used this arduino library for the PN532 https://github.com/elechouse/PN532 It basically worked first time on the SPI but I only had 3 pins left so tried to switch to UART 2. Changed this in the ...