FujiNet for CoCo: The Basics

Everything you need to get up and running with FujiNet on the Tandy Color Computer.

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Chapter 1 — Introduction

What is FujiNet?

FujiNet is a multi-function peripheral device for classic computers — including your Tandy Color Computer. It connects to your CoCo's cartridge port and gives it abilities it never had before: network access, virtual disk drives, a real-time clock, and more.

By the time you finish this guide, you'll be mounting disk images and loading programs from across the internet.

FujiNet's origins

FujiNet was originally developed for the Atari 8-bit family and has since been expanded to support many classic computers, including the CoCo. The community is active and growing!

What can FujiNet do for your CoCo?

• Load disk images (.DSK files) from a local SD card or a network server
• Connect your CoCo to a Wi-Fi network
• Use virtual disk drives — no physical disks required
• Access online resources directly from your CoCo

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Chapter 2 — Hardware Setup and Installation

What you'll need

Other than your FujiNet and your CoCo, you'll need a MicroSD card formatted in FAT32.

MicroSD card recommendations

Use a 64 GB or smaller card (8–32 GB is more than adequate). Stick with a known reliable brand such as SanDisk or Transcend.

To format FAT32 on Windows: insert the card, right-click it in Explorer, choose Format, select FAT32, and proceed.

Configure the DIP switches for your CoCo model

Your FujiNet has a pair of DIP switches on top that must be set to match your CoCo model. These select the serial port speed and the correct HDB-DOS ROM:

Computer	DIP 1	DIP 2	Serial speed
CoCo 1	ON	ON	38,400 bps
CoCo 2	OFF	ON	57,600 bps
CoCo 3	ON	OFF	115,200 bps
Dragon 32/64	OFF	OFF	—

CoCo 3 double-speed mode

FujiNet uses HDB-DOS which employs the "double speed poke" to achieve 115,200 bps on CoCo 3. This is a feature of HDB-DOS and DriveWire, not FujiNet itself.

To disable double-speed mode temporarily, type at the OK prompt:

POKE65497,0:POKE65496,0

Note that HDB-DOS will re-enable it automatically whenever disk I/O through FujiNet is accessed.

Connecting the hardware

1. Turn off your Color Computer.
2. Insert your MicroSD card into the FujiNet slot.
3. Insert your FujiNet into the cartridge port on the right side of the CoCo.
4. Plug the cable into the SERIAL I/O port on the back of your CoCo.
5. Power on your CoCo.

Power off before connecting

Always turn off your CoCo before inserting or removing the FujiNet device. Plugging it in with power on can damage your hardware.

Initial power-on

If FujiNet is connected properly, you'll see a message that the FujiNet config is loading, followed quickly by the network configuration screen:

If you don't see this screen, try:

• Check that FujiNet is firmly seated in the cartridge port
• Make sure your SD card is properly inserted
• Ensure the contacts on the card edge of the FujiNet cartridge are clean
• Ask for help on the FujiNet Discord or Facebook group

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Chapter 3 — The Configuration Program

The configuration program is FujiNet's built-in control panel. It lets you manage your Wi-Fi network, disk images, device settings, and more.

Starting the configuration program

The configuration program starts automatically when you power up your CoCo with FujiNet inserted.

To restart it from a BASIC prompt, press RESET on the back of the CoCo, then type:

DOS

The Network Configuration Screen

The first screen you see on power-up is the network selection screen:

The screen lists nearby Wi-Fi networks (name on the left, signal strength in asterisks on the right).

Key	Action
↑ / ↓	Move between networks
H	Enter a hidden network name (one that doesn't broadcast its SSID)
R	Rescan for networks
Enter	Select highlighted network

After pressing Enter, you'll be prompted for the network password. Characters are masked with * as you type. Lowercase by default; hold Shift for uppercase. Press Enter to connect.

On successful connection, you'll be taken to the Host Slots screen.

The Host Slots Screen

Your FujiNet loads programs by connecting disk image files — on your SD card or a network server — to drive slots. There are 8 host slots.

Slot 1 — SD card: The first slot is reserved for your SD card and must always be named SD (in all caps). This is set automatically.

Slots 2–8 — Network servers: Enter TNFS server hostnames or IP addresses. Example: tnfs.fujinet.online.

Finding TNFS servers

A current list of community TNFS servers is available at fujinet.online/tnfs-server-status.

Key	Action
1–8 or ↑/↓ + E	Edit a host slot
Enter on a host	Browse its files
L	Boot to the FujiNet Game Lobby (multiplayer games)
C	Open the Configuration screen
→	Open the Drives screen
Break	Exit CONFIG, mount selected images, and reset CoCo

Game Lobby

Pressing L loads the FujiNet Game Lobby where you can play online multiplayer games (Five Card Stud, Battleship, Fujitzee) against players on other 8-bit computers. If the L command isn't yet in your firmware, load it manually: set a host slot to tnfs.fujinet.online, navigate to the COCO directory, and load LOBBY.DSK.

The Configuration Screen

Press C from the Hosts screen to open the Configuration screen:

This screen shows: - Currently connected Wi-Fi SSID - FujiNet hostname - IP address, netmask, DNS - MAC address and BSSID - Firmware version (FNVER)

Key	Action
C	Change SSID (returns to network selection screen)
R	Reconnect to the current network
Any other key	Return to Host Slots screen

The Drives Screen

Press → from the Host Slots screen to open the Drive Slots screen:

Like standard CoCo DECB, there are 4 drive slots numbered 0–3. A color indicator next to each slot shows read-only or read-write status.

Key	Action
0–3 or ↑/↓	Select a drive slot
R	Set selected slot to read-only
W	Set selected slot to read-write
E	Eject the image from the selected slot
Clear	Eject all drive slots
←	Return to Host Slots screen
Break	Exit CONFIG and reset CoCo

Read-write mode

Only use Write mode when working with a disk image on your own SD card or local server. Never write to a shared network image.

Navigating host folders and selecting a disk image

Press Enter on a populated host slot to browse its files:

The top of the screen shows the host name and current directory path. Entries ending with / are directories.

Key	Action
↑ / ↓	Move up/down the list
Enter	Enter a directory or select a file
←	Go up to the parent directory
Shift+↑ / Shift+↓	Jump to previous/next page
F	Enter a filter (e.g. W*.* shows files starting with W; !word recursively searches subfolders)
N	Create a new 157k floppy disk image (SD card only)
C	Copy a disk image to another host/folder

Long filenames

Filenames longer than 32 characters are "ellipsized" — the config shows the first and last few characters with ... in the middle. Hovering on a long filename for 5 seconds scrolls the full name.

To select a disk image, navigate to a .DSK file and press Enter:

The screen shows the file's modification time, size, and name. Use arrow keys to select the drive slot, then:

Key	Action
Enter	Mount read-only
W	Mount read-write
Break	Cancel

After mounting, you'll return to the file browser in the same location.

When you've mounted all the images you need, press Break at the Host Slots screen to exit CONFIG. The CoCo resets and returns to an OK prompt with your drives mounted.

Autostart

If the disk image in drive slot 0 contains a file named AUTOEXEC.BAS, HDB-DOS runs it automatically on reset — this is how the CONFIG program itself launches on power-up.

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Chapter 4 — Working with Disk Images in HDB-DOS

FujiNet uses HDB-DOS — an extended version of standard Tandy Disk Extended Color BASIC (DECB). In addition to standard DECB commands (DIR, LOAD, LOADM, RUN), HDB-DOS adds several useful features:

AUTOEXEC.BAS

On power-up, HDB-DOS automatically looks for and runs AUTOEXEC.BAS on the disk image in drive slot 0. The DOS command re-initiates this.

Note

This is how the CONFIG program auto-launches when you power up with FujiNet. Pressing Reset re-loads the CONFIG disk so you can type DOS to restart CONFIG.

RUNM

Standard DECB requires two steps to run a binary executable:

LOADM "PROGRAM.BIN"
EXEC

HDB-DOS shortens this to one command:

RUNM "PROGRAM.BIN"

DRIVE

In standard DECB, you switch drives with DRIVE X. In HDB-DOS, use the # symbol:

DRIVE #1

This switches to the disk image mounted in drive slot 1.

FLEXIKEY

HDB-DOS adds command-line editing shortcuts:

Key	Action
→ (one at a time)	Recall the last command character by character
Shift+→	Recall the entire last command at once
← (one at a time)	Delete the last character (same as Backspace)
Shift+←	Clear the entire current line

More HDB-DOS features

For a full reference, see the HDB-DOS User Manual. Note: some HDB-DOS features relate to real hard drives and don't apply to FujiNet. The FujiNet team did not write HDB-DOS and cannot modify it.

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Chapter 5 — FujiNet CoCo Programs

The FujiNet game lobby gives access to multiplayer games. Beyond that, several standalone network-aware programs are available.

News

FujiNet News connects to a web server that aggregates news stories from multiple sources. Pick a topic, scroll through headlines, and read full articles — all on your CoCo.

• CoCo 1 & 2: supports 32-column and 42-column (with real lowercase) display
• CoCo 3: also supports native 40- and 80-column modes

Location: tnfs.fujinet.online/COCO/NEWS.DSK

Weather

FujiNet Weather retrieves current conditions and forecasts from a free web service. Your location is detected from your FujiNet's IP address automatically, or you can enter any location manually. Toggle between Imperial and Metric units and refresh at any time.

Location: tnfs.fujinet.online/COCO/WEATHER.DSK

Netcat

FujiNet Netcat is a simple terminal program for telnetting to online BBSes and other Telnet services. Connect using the URL format:

N:TELNET://MYBBSEXAMPLE.COM:PORT

Uses a 42-character soft font with VT-52 (monochrome) compatibility. If your favorite BBS supports VT-52 terminal emulation, use Netcat for the best experience.

Location: tnfs.fujinet.online/COCO/NETCAT.DSK

Wiki

FujiNet Wiki searches Wikipedia. Enter a subject, select from the results, and read full articles on your CoCo.

• CoCo 1 & 2: 42-column upper/lowercase soft font
• CoCo 3: also supports native 40/80 column formats

Location: tnfs.fujinet.online/COCO/WIKI.DSK

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Chapter 6 — Appendix

Firmware updates

FujiNet firmware is updated using the FujiNet-Flasher tool.

Requirements: - USB-A to USB-mini cable - Silicon Labs CP210x USB bridge driver — download from silabs.com (Windows: right-click silabser.inf → Install) - FujiNet-Flasher for your OS

Flashing steps:

1. Power down your CoCo.
2. Connect the USB cable between your PC and FujiNet.
3. Open FujiNet-Flasher.
4. Select the serial port (usually only one listed).
5. Leave baud rate at 460800.
6. Select Tandy CoCo from the firmware dropdown, then choose the firmware version (use the latest).
7. Click Flash FujiNet Firmware.
8. Hold down the A button on your FujiNet (the one closest to the front) until the flashing process starts writing — then release.
9. Once complete, disconnect the USB cable before powering up your CoCo.

Nightly builds

Nightly/pre-release builds are available at github.com/FujiNetWIFI/fujinet-firmware/releases/tag/nightly — look for files starting with fujinet-COCO. These are provided AS-IS with no guarantee they will work. Only use them if you're prepared to troubleshoot on your own.

Debug logging

To view FujiNet's debug log:

1. Connect the USB cable.
2. Open FujiNet-Flasher.
3. Click Serial Debug Output.

You'll see live debug messages as your CoCo accesses FujiNet.

TNFS

TNFS is the file server protocol FujiNet uses to stream disk images over the internet. You can run your own local TNFS server to access software on your PC, Mac, or Linux server.

Setup guide: github.com/FujiNetWIFI/fujinet-firmware/wiki/Setting-up-a-TNFS-Server

Software development in C for FujiNet

To write CoCo software that uses FujiNet, you'll need:

Tool	Link
CMOC C compiler	CMOC homepage
LWTools assembler/linker	lwtools.ca
Color Computer Toolshed (disk image utilities)	GitHub
fujinet-lib (C library for FujiNet)	GitHub
MekkoGX build system (cross-platform Makefiles)	GitHub

Tip

It's highly recommended to do all FujiNet development in Linux or a Linux VM. Ask questions in the #development channel on Discord.

Resources and community links

Resource	Link
FujiNet website	fujinet.online
FujiNet firmware wiki	github.com/FujiNetWIFI/fujinet-firmware/wiki
Facebook users group	facebook.com/groups/fujinetusers
Discord server	discord.gg/7MfFTvD

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Revision: 2026-03-02 · Converted to FujiNet mkdocs documentation site.