Touchscreen smart phone prototype built around the A7670C 4G cellular module with dialer, SMS, inbox, and settings UI.
Overview
This product is a custom embedded smart phone concept using an A7670C 4G module and a touchscreen interface. The UI includes phone-style screens such as dialer, SMS, inbox, and settings, plus a full on-screen keyboard for composing messages. It is designed as a hands-on cellular terminal that demonstrates how a microcontroller can manage a 4G modem, touch display, and phone-like workflow without relying on a commercial smartphone OS.
Touchscreen UI collects user actions, the controller translates them into modem commands, and the A7670C module executes cellular functions such as SMS and network operations.
Project photos
SMS center with touchscreen keyboard and send button.
Retro phone menu with dialer, SMS, inbox, and settings.
Implementation details
Firmware
Firmware presents a phone-like menu, handles touch input, builds SMS text through an on-screen keyboard, and communicates with the A7670C module using AT commands for cellular functions.
Power
Powered from a bench supply during prototyping, with attention to the high transient current required by cellular modules during network registration and transmission.
Components / BOM
A7670C 4G module, ESP32-class development board, Touch TFT display, SIM card, Power supply and wiring
Engineering challenges
Cellular modules require stable power and reliable AT-command state handling. Touchscreen UI also needs clear state transitions so the dialer, SMS, inbox, and settings screens feel like one product.
Solutions
Built a retro phone-style interface and a dedicated SMS keyboard screen, separating the phone application from the lower-level modem command flow.
Results & metrics
Demonstrated phone menu UI and SMS composition workflow on physical touchscreen hardware.
Future improvements
Add call handling, contact storage, message history persistence, battery management, speaker/microphone audio path, and a compact enclosure.
