16-Year-Old Builds His Own Open-Source Cell Phone Based On An ESP32
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 well as all of the support circuitry for charging it as well as a USB interface that can comm ...continues
See https://gadgeteer.co.za/16-year-old-builds-his-own-open-source-cell-phone-based-on-an-esp32/