MOSFET Delay ESP32 – How to Implement a Delay Circuit After Power On for ESP32

delayesp32mosfetp-channel

I'm using the ESP32 with a sensor connected to UART0 and I want to suppress the first stage bootloader log, since it can lead to delayed response of the sensor later on.

Therefore I want to pull the IO15 pin to GND during the first second of power being connected to the 3.3V rail. Pulling IO15 to GND during the first stage bootloader causes it to suppress logs to UART0.
After that second the pin should be left floating so I can still use it for JTAG operations.

I tried a P channel MOSFET in this configuration:

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I thought this way the MOSFET conducts first and then as voltage rises by charging the capacitor it opens and leaves the IO floating but it did not work. Thanks for any help!

Best Answer

Try it the other way around.

Use a N-Channel MOSFET. You need a low-threshold MOSFET like the Trench-Fet family.

Source goes to Ground, Drain to the pin to drag Low. Capacitor from Vdd to the MOSFET gate along with a resistor from gate to Ground. Add a signal diode in parallel with the resistor (A to ground, C to the gate) to discharge the capacitor when Vdd is removed.

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