RetroBox Modem is still under active development, so these instructions describe the current working architecture rather than a finalized production design. Some components, mounting details and interfaces may change as the project evolves.

1. Prepare the main controller

RetroBox is built around a small Linux-capable single-board computer with WiFi connectivity.

The controller handles the Hayes command interpreter, network connections, OLED interface, status LEDs, modem audio and serial communication with the host computer.

For modern computers, the system can expose a USB serial interface directly.

2. Connect the OLED display

A small monochrome OLED display is connected to the controller and used to show useful modem information such as:

• IP address
• WiFi signal
• current modem state
• connection status
• dialing and online information

The display allows RetroBox to provide useful feedback independently of the computer connected to it.

3. Add the modem audio hardware

A digital audio output stage and small internal speaker reproduce the sounds associated with dialing and modem negotiation.

The firmware handles dialing tones, carrier sounds and handshake sequences for different modem personalities.

Audio is one of the areas still under active development, as the goal is to make the different connection profiles sound as authentic as possible rather than simply playing one generic modem recording.

4. Wire the front-panel indicators

The front panel follows the style of traditional external modems and includes the following indicators:

WIFI AA OH SD RD TR CS CD

A separate PWR indicator shows that the modem is powered.

The firmware controls the LEDs according to WiFi state, connection status, serial activity and modem operation.

5. Add modern and vintage serial connectivity

Modern computers can communicate with RetroBox through USB serial.

Vintage computers can use a traditional RS-232 connection through a serial level-conversion stage.

This allows an older machine to communicate with RetroBox in the same way it would communicate with a conventional external modem.

The basic architecture is:

Computer → Serial / USB → RetroBox → WiFi → TCP/Telnet → BBS

The computer only sees the modem interface. WiFi and network communication are handled internally by RetroBox.

6. Install the firmware

The RetroBox firmware implements the Hayes-compatible command layer, network handling, modem states, display interface, LEDs, sounds and configuration system.

Once the firmware is running, opening a serial terminal and typing:

AT

should return:

OK

A BBS can then be dialed using:

ATDhostname:port

RetroBox establishes the network connection internally and returns the appropriate modem result code to the host computer.

Other supported modem-style functions include escape sequences, returning online, persistent configuration, favorites and connection history.

7. Print and assemble the enclosure

RetroBox uses a custom 3D-printed enclosure designed to resemble the external modems and peripherals commonly found beside computers during the dial-up era.

The enclosure consists of a cream-colored body and a contrasting front panel with integrated lettering.

The design has gone through multiple physical revisions to refine:

• OLED positioning
• LED alignment
• switch fit
• PCB mounting
• connector placement
• internal clearances
• ventilation
• lettering and two-color printing

Because the hardware is still evolving, some internal mounting points and dimensions may change between prototype revisions.

8. Test the modem

Connect RetroBox to a terminal program and verify the Hayes command interface:

AT

OK

Then dial a BBS:

ATDhostname:port

RetroBox handles the network connection internally and returns:

CONNECT

From that point, the computer communicates with the remote BBS through the RetroBox Modem.

Different modem personalities and data-pacing settings can then be used to experiment with the experience of different dial-up speeds.

Prototype note

RetroBox Modem is still a work in progress.

The enclosure, firmware, serial interfaces, audio system and some hardware components are continuing to evolve. These instructions document the current working prototype and the general architecture of the project rather than a final production version.