How to send from ESP32 to Arduino?

Question

I am using ESP32 to read a temperature sensor and I wont to send this reading to Arduino to act according to different reading

what should be the connection between the ESP32 and Aruido?

Answer 1

Should is not the appropriate word, I would suggest to use the UART (Serial.print() and Serial.read()). Because the ESP has an operating voltage of 3.3V and Arduino 5V, you must use a level shifter.