I made a circuit with arduino and A6 GPRS module sending an sms when the connection between two wires is broken (trigger, with 100K pull-down resistor). This works fine.
To make things smaller, I am trying to build a similar project with the Lilygo TTGO T-call ESP32 SIM 800L
I read “The pins on the board are directly connected to the ESP32 chip and are therefore only suitable for 3.3V signals.”
If I am making a trigger with a wire between 3.3V and a GPIO and the ground, what should be the value of the resistor ?
(U=RI … 3.3V=RI … but where do I find the maximum current) ?