World's Smallest Programable INDUSPHONE DESIGN

This is the second part of designing the world’s smallest phone, where the UI is integrated with the basic functions of the phone.

- ASHWINI KUMAR SINHA

Previously, the Indusphone user interface (UI) was designed and the GSM module was tested, integrating it with the IndusBoard coin to advance the design. This segment combines the UI with such functions as contacts and calculator. The connections established in part 1, published in EFY’s October issue, remain unchanged. The focus now shifts to software and UI integration for the IndusBoard phone.

The initial step involves integrating fundamental functions like dialling a number, making calls, checking call status, handling incoming calls, and displaying the idle screen within the previously designed UI. Fig. 1 illustrates the IndusBoard phone.

Integrating the calling system

In the code, the GSM call library and the TFT_eSPI libraries combine into a single codebase. An idle screen is created to monitor incoming calls, battery status, and signal strength in a continuous loop. When a call comes in, the UI transitions to display the ‘attend’ and ‘end’ buttons. The function to attend the call is activated when the attend button is touched on the UI. The code checks the UI input; if the input is ‘attend’ or ‘end,’ it navigates to the corresponding screen and executes the appropriate function using the `call.answer();` and `call.hangup();` commands. Fig. 2 provides a code snippet for TFT_ eSPI, while Fig. 3 depicts the initial idle screen code, which checks for incoming calls, network connectivity, and battery levels.