The SPI routines in the ESP32 Arduino port both work just fine ... use the microcontroller’s pullup resistors to pull the I2C bus lines high, so I tested that out by pulling the 10 KOhm ...

(Google Translate from French) The phone uses an ESP32 at its core, with a SIM800L GSM modem to interact with the cell network, including retrieving the system time. A small battery is included as ...