Phone Zero

A working accessibility device for elderly blind users

Project Status: PROOF OF CONCEPT ⚡

Phone Zero Prototype v0.2.0 successfully validates core GSM communication capabilities using ESP32-WROOM-32 and SIM900A. We have confirmed the ability to place calls, answer calls, send SMS, and receive SMS. This is a proof of concept stage - significant development work remains for a complete accessibility device.

Current Implementation (Prototype v0.2.0):

• ESP32-WROOM-32 microcontroller with reliable hardware UART2 communication
• SIM900A GSM module for voice calls and SMS (✅ validated)
• Basic button input detection and SMS command processing
• Audio output tested via earphone jack (good quality)
• Single power supply confirmed for both ESP32 and SIM900A

What We DON'T Have Yet:

• Microphone and speaker integration
• Audio amplifiers and echo cancellation hardware
• Extended reliability testing (1+ week operation)
• Proper component organization (currently breadboard prototype)
• Complete software implementation (currently < MVP level)

Hardware Components

Working Configuration:

• ESP32-WROOM-32 development board (DoiT ESP32 DevKit v1)
• SIM900A GSM/GPRS module powered via JZK XL4015 DC-DC converter
• JZK XL4015 step-down converter (4-38V to 1.25-36V, max 5A) ⭐ PROMISING HARDWARE
• 8 tactile push buttons connected to GPIO pins with internal pull-ups
• Single power supply solution with shared ground

Connections:

• SIM900A TX → ESP32 GPIO16 (UART2 RX)
• SIM900A RX → ESP32 GPIO17 (UART2 TX)
• SIM900A GND → ESP32 GND (shared ground)
• Power: JZK XL4015 DC-DC converter → both ESP32 and SIM900A

Button Mapping:

• Button 1: GPIO4 | Button 5: GPIO22
• Button 2: GPIO18 | Button 6: GPIO23
• Button 3: GPIO19 | Button 7: GPIO25
• Button 4: GPIO21 | Button 8: GPIO26

Key Features (Implemented)

• 8 Speed Dial Buttons: Instant calling with tactile button feedback
• SMS Programming: Remote configuration via authorized phone numbers
• SMS Relay: Forward messages through the device to other numbers
• Persistent Storage: Phone numbers saved to ESP32 flash memory
• Hardware UART: Reliable communication using ESP32 UART2
• Memory Management: Automatic SMS cleanup for privacy
• Network Status: Signal quality monitoring and network registration

SMS Commands

The device accepts SMS commands from authorized numbers:

• SET 1 +1234567890 - Program speed dial button 1-8
• LIST - Get current speed dial numbers
• STATUS - Check device status
• SMS "message text" +1234567890 - Send SMS to another number

Project Structure

phone-zero/
├── ESP_GSM/                    # Main firmware (PlatformIO project)
│   ├── src/main.cpp           # Complete Phone Zero implementation
│   └── platformio.ini         # Build configuration
├── docs/                      # Documentation and specifications
│   ├── prototype-v0.2.0/     # Current working prototype documentation
│   ├── boards/               # Hardware pinout diagrams and photos
│   ├── MVP/                  # MVP requirements and milestones
│   └── *.md                  # Technical documentation
└── private/                  # Market research and private notes

Getting Started

Prerequisites

• PlatformIO IDE or VS Code with PlatformIO extension
• ESP32-WROOM-32 development board
• SIM900A GSM module with 5V/2A power supply
• Valid SIM card with voice and SMS capabilities

Setup Instructions

1. Hardware Setup:

   • Connect ESP32 and SIM900A as described in hardware section
   • Insert activated SIM card into SIM900A module
   • Power SIM900A with independent 5V/2A supply

2. Firmware Upload:

   cd ESP_GSM
   pio run --target upload

3. Configuration:

   • Update authorized phone numbers in main.cpp
   • Set default speed dial numbers via SMS commands
   • Test button functionality and call features

Usage

1. Making Calls: Press any programmed button (1-8) for instant speed dial
2. Programming: Send SMS "SET 1 +1234567890" to program button 1
3. Status Check: Send SMS "STATUS" to verify device operation
4. SMS Relay: Send SMS "SMS 'Hello!' +1234567890" to forward messages

Documentation

• Prototype v0.2.0 - Current proof of concept with GSM communication validation
• Hardware Requirements - Component specifications and requirements
• Phone Specifications - Core features and accessibility design
• MVP Requirements - Minimum viable product documentation
• Board Layouts - Hardware pinout diagrams and reference photos

Future Enhancements

• Physical enclosure design with tactile button layout
• Battery backup system for power outage protection
• Enhanced audio quality with dedicated codec
• Call answering via button press functionality
• Battery status monitoring via SMS notifications
• 3D printed enclosure for production units

Contributing

Phone Zero is a working accessibility device. Contributions welcome for hardware improvements, firmware enhancements, and documentation updates.

License

[License information to be added]