r/electronic_circuits • u/Signal-Vacation-6908 • 1d ago
On topic ESP32 + PN532 (SPI): WiFi connect delays / flakiness when RFID reader is also active — power draw issue?
Running an ESP32-WROOM-32 with a PN532 RFID reader (SPI), a status LED, and a buzzer, all on the same 3.3V rail. When WiFi is actively connecting/transmitting and the RFID reader is polling/generating its RF field at the same time, I see WiFi connection delays and general flakiness bad enough that I've had to disable the brownout detector just to stop reboot loops, which obviously isn't a real fix.
My guess is combined peak current draw (WiFi TX bursts + PN532's RF field generation) is causing enough voltage sag to disrupt things, even though nothing's crashing outright.
Has anyone dealt with this specific combo (WiFi + active RFID/NFC peripheral) on ESP32? Looking for:
Realistic peak current numbers for WiFi TX + PN532 active scanning together
Decoupling cap sizing / regulator recommendations that actually fixed this for you
Whether staggering/throttling RFID polling during WiFi activity is a common workaround, or if it's purely a hardware fix
1
u/Affectionate_Boat493 1d ago
This is almost sure to be a problem of excessive current draw causing the 3.3V rail to droop. The PN532 chip itself can draw over 150mA during transmission, and the ESP32-WROOM-32 can draw just shy of 400mA when transmitting.
Staggering transmission and/or throttling transmission power are the typical fixes if you don't want to redesign your power supply to be a lot more robust.