RS-232 (MS-DOS PC) Quickstart Guide

Welcome to the FujiNet quickstart guide for RS-232 serial connections. FujiNet RS-232 currently targets MS-DOS (PC-compatible) systems via a standard serial port. Support for other serial devices may be added in the future. For a broader overview of all supported platforms, see the Platform Overview.

Beta Notice: FujiNet RS-232 support is under active development. Some features (notably the on-screen CONFIG application) are not yet fully functional. Join the FujiNet Discord for the latest updates.

Hardware

Overview

The RS-232 FujiNet uses the newer ESP32-S3 chipset (rather than the original ESP32 used by other FujiNet variants). The ESP32-S3 provides similar functionality with some beneficial upgrades.

Connection Diagram

flowchart LR
    PC[DOS PC\nCOM port] -->|RS-232 serial cable| FN[FujiNet RS-232\nESP32-S3]
    FN -->|WiFi| NET[Network / Internet\nTNFS servers]
    FN -->|SD card| SD[Local Storage\nfnconfig.ini, disk images]
    USB[USB-C Power\n5V / 1A minimum] --> FN

Power Requirements

FujiNet RS-232 requires a standard 5V USB-C power source providing at least 1 amp.

Important: Power on the FujiNet before powering on your PC. This ensures FujiNet is ready to respond when DOS loads the driver.

Software Setup

Installing the DOS Driver

A DOS device driver is required for your PC to communicate with FujiNet.

Download the latest driver from the fujinet-rs232 releases page. The most recent version will be at the top.
Expand the “Assets” section and download the .sys file.
Rename the file to FUJINET.SYS.
Copy FUJINET.SYS to your system’s boot disk or drive.
Add the following line to your CONFIG.SYS:

DEVICE=FUJINET.SYS

Reboot to load the driver.

Driver Configuration Options

The driver supports two optional parameters:

Parameter	Default	Description
`FUJI_PORT`	`1`	COM port number FujiNet is connected to (1, 2, 3, etc.)
`FUJI_BPS`	`115200`	Baud rate for serial communication

Example CONFIG.SYS with custom settings:

DEVICE=FUJINET.SYS FUJI_BPS=9600 FUJI_PORT=2

Baud Rate Troubleshooting

If your computer hangs when accessing FujiNet-mounted drives, try lowering the baud rate. Test progressively slower speeds until you find one that works reliably:

Speed	Notes
115200	Default – fastest, works on most systems
57600	Try this first if 115200 causes hangs
38400	Good for older or slower systems
19200	Conservative speed
9600	Most compatible, slowest

Important: If you change the baud rate in CONFIG.SYS, you must also update the FujiNet’s fnconfig.ini file on the SD card to match:

[RS232]
baud=9600

Connecting to WiFi

The on-screen CONFIG application is not yet fully functional for RS-232. To configure WiFi, manually edit the fnconfig.ini file on the FujiNet’s SD card:

Remove the SD card from FujiNet.
Insert the SD card into your modern computer.
Edit (or create) the fnconfig.ini file with your WiFi credentials. See the fnconfig.ini reference for the full format.
Insert the SD card back into FujiNet.
Power cycle FujiNet.

Setup Flow

flowchart TD
    A[Download FUJINET.SYS driver] --> B[Copy to boot disk]
    B --> C[Add DEVICE= line to CONFIG.SYS]
    C --> D[Edit fnconfig.ini on SD card\nwith WiFi credentials]
    D --> E[Insert SD card into FujiNet]
    E --> F[Power on FujiNet via USB-C]
    F --> G[Power on PC and boot DOS]
    G --> H[Access FujiNet via web UI\nor mounted drives]

Web User Interface

Once FujiNet is connected to your WiFi network, you can manage it through its built-in web interface:

Open a browser on any device connected to the same network.
Navigate to http://fujinet.local or the IP address assigned to your FujiNet.
From the web interface, you can mount disk images, browse TNFS servers, and manage FujiNet settings.

FujiNet-Enabled Applications

Some FujiNet-enabled applications are available for MS-DOS:

Source code is in the fujinet-rs232 repository
Apps can be built with the Open Watcom compiler
Precompiled versions are available on the apps.irata.online TNFS server

FujiNet Documentation