CoCoWiFiModem

A WiFi modem for retro computers, specifically the Tandy Color Computer (CoCo), using the ESP8266 microcontroller.

Overview

This project implements a virtual modem using the ESP8266, allowing vintage computers to connect to modern networks and BBSs over WiFi. The firmware emulates Hayes modem commands and provides RS-232 connectivity for seamless integration with retro hardware.

Features

• Hayes-compatible AT command set
• WiFi connectivity for vintage computers
• OLED display support for status information
• EEPROM storage for configuration persistence
• Customizable baud rates via software serial
• Open source and fully modifiable

Hardware Requirements

• ESP8266 microcontroller (NodeMCU, Wemos D1 Mini, or similar)
• Optional: 4-pin OLED display (I2C - 128x64 recommended)
• RS-232 level shifter (MAX3232 or equivalent)
• Power switch (optional)
• Connecting cables

Pin Configuration

                  +-----------------+
                  |   WiFi Antenna  |
        ADC0  A0  |                 | D0  GPIO16 (WAKE) - Power switch to GND
   Reserved  RSV  |  +-----------+  | D1  GPIO5  (SCL)  - OLED I2C Clock
   Reserved  RSV  |  |  ESP8266  |  | D2  GPIO4  (SDA)  - OLED I2C Data
SDD3-GPIO10  SD3  |  |           |  | D3  GPIO0  (FLASH)
 SDD2-GPIO9  SD2  |  |           |  | D4  GPIO2  (TXD1/FLASH)
SDD1-MOSI   SD1   |  |           |  | 3.3V
SDCMD-CS    CMD   |  +-----------+  | GND
SDD0-MISO   SD0   |                 | D5  GPIO14 (SCLK) - Spark OLED
SDCLK-SCLK  CLK   |                 | D6  GPIO12 (MISO) - Spark OLED
            GND   |                 | D7  GPIO13 (MOSI/RXD2) - RX from RS-232 TX
           3.3V   |                 | D8  GPIO15 (CS/TXD2)   - TX to RS-232 RX
             EN   |                 | RX  GPIO3  (RXD0)
            RST   |                 | TX  GPIO1  (TXD0)
            GND   |                 | GND
            Vin   |                 | 3.3V
      USB/Flash   |                 | RST
                  +-----------------+

Pin Assignments

Pin	GPIO	Function	Notes
D1	GPIO5	I2C SCL	OLED display clock
D2	GPIO4	I2C SDA	OLED display data
D7	GPIO13	Serial RX	Connects to RS-232 TX
D8	GPIO15	Serial TX	Connects to RS-232 RX
D0	GPIO16	Power Switch	Optional switch to GND
D5	GPIO14	SCLK	For Spark integrated OLED
D6	GPIO12	MISO	For Spark integrated OLED

Software Dependencies

• SoftwareSerial - Serial communication on non-default pins
• ESP8266WiFi - WiFi functionality
• EEPROM - Configuration storage
• WiFiClient - TCP/IP client functionality

Installation

1. Install the Arduino IDE with ESP8266 board support
2. Install required libraries via Library Manager
3. Clone or download this repository
4. Open the .ino file in Arduino IDE
5. Select your ESP8266 board type
6. Configure WiFi credentials in the code (or via AT commands)
7. Upload to your ESP8266

Usage

1. Connect the ESP8266 to your vintage computer via RS-232
2. Power on the modem
3. Configure WiFi settings using AT commands
4. Connect to remote systems using standard modem commands

Basic AT Commands

AT              - Test connection
ATI             - Display information
ATE0/ATE1       - Echo off/on
ATDT<host:port> - Dial (connect to) host
ATH             - Hang up
+++             - Enter command mode

Resources

• Icons: Icons8 Phone Icon Set
• OLED Bitmap Tool: image2cpp

Author

Reinaldo Torres
CoCoByte Club
reyco2000@gmail.com
March 7, 2023

Acknowledgments

Parts of this program were developed with assistance from ChatGPT, a large language model by OpenAI.

License

This code is free and open source. You may use, modify, and distribute it for any purpose. Schematics and hardware designs will be made publicly available.

Contributing

Contributions are welcome! Feel free to submit issues, fork the repository, and create pull requests.

Future Plans

• Detailed schematics publication
• PCB design files
• Web-based configuration interface
• Additional terminal emulation support