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Gotek Floppy Mods

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1. Introduction

The GoTek USB floppy emulator is a device that allows one to connect floppy disk images stored on a USB stick to a physical IBM PC floppy disk interface. This is a device we use ubiquitously in our retrocomputing pursuits, and this page is a record of the modifications and procedures we use in conjunction with the custom flashfloppy firmware on this device.

2. Hardware Modification

Most of these modifications are taken from the FlashFloppy Wiki, though the information has been condensed based on a "standard" build that we do for every Gotek that we use.

The information here applies to the current revision of the Gotek floppy emulator as of this writing, using the Artery microcontroller and with the jogdial header present... older revisions do not have the jogdial header and newer revisions may have other issues. Make sure the headers in the diagram below are available! Check the wiki if in doubt!

Please note that it may be advisable to flash the firmware first, as plugging in the USB cable for that may cause the speaker to emit a constant, irritating screech until firmware is flashed. These modifications REQUIRE the FlashFloppy firmware to be used!

2 - 1. Bill of Materials

2 - 2. Diagram

Diagram of the GoTek mainboard, with the jumper/connection blocks called out with their pins highlighted in colors that correspond to the pins on an additional rotary dial, OLED display, and speaker (with transistor for amplification).

3. Photos

Front view of our modified Gotek floppy emulator. Top view of the inside of one of our modified Gotek floppy emulators.

4. Flashing and Software

4 - 1. Firmware Flashing

This is fairly standard, according to the FlashFloppy Wiki. The script below will flash a Gotek connected via a double-A-ended USB cable and with the jumper wire installed as per the FlashFloppy wiki page.

If the firmware does not flash with this procedure, make sure you have the jumper wire installed and try running the script several times!
5# First, run the unprotect command (needs -D, even tho it doesn't use the file).
6# This will probably generate an error, but it's fine.
7sudo dfu-util -s :unprotect:force -D $DFU_FILE -a 0
9sleep 3
11# Perform the actual flash.
12sudo dfu-util -D $DFU_FILE -a 0

4 - 2. Companion Software

Once FlashFloppy is running, the OLED display should show the current version when power is applied. The vfloppy repository contains some scripts for working with floppy images from ZIP files and directories on the Linux command line via mtools.

5. Floppy Server

If your retrocomputer is connected to a KVM and stowed out of the way, you may also want to be able to change the floppy at a distance. This is doable using a Raspberry Pi Zero W connected to the USB port of the Gotek via USB-OTG.

5 - 1. Hardware

You will need a Raspberry Pi Zero W with appropriate power supply. You will also need a USB-A to Micro-USB-B cable with the power (usually red) wire disconnected! This is important! You can use a breakout board or just cut the cable and only rejoin the green, white, and black wires. But the red wire MUST be disconnected! We are not responsible for any damage that may occur as a result of failure to do this (or from anything else here, for that matter)!

Once you have these things:

5 - 2. Software

The Raspberry pi will presents a constructed "container" image which contains both a floppy image and an FF.CFG file which automatically loads that image to the Gotek via the USB-OTG layer.

The "container" image is assembled by a simple piece of software called floppcgi, which runs as a FastCGI daemon sitting behind nginx. This daemon then responds to web requests, presenting a web page for selecting the image to use.

This section assumes a standard installation of the current version of the Raspbian OS Lite image. It was tested with Buster, but hopefully future versions should work with minimal modification.

It is highly recommended to use the Raspberry Pi Imager utility to flash the imager, as this allows you to setup your wireless network without connecting a display and keyboard to your Raspberry Pi Zero.

The script below is simplified, to illustrate the steps to getting it working. It assumes running as root and lacks idempotence. A more robust is included in the floppcgi repo.
# Install required packages.
apt install nginx libfcgi-dev mtools git
# Add dwc2 overlay for USB Gadget support.
echo "dtoverlay=dwc2" >> /boot/firmware/config.txt
# Add dwc2 module for USB Gadget support.
echo "dwc2" >> /etc/modules
# Copy the site config to nginx.
cp floppcgi.nginx /etc/nginx/sites-available/floppcgi
ln -s /etc/nginx/sites-available/floppcgi /etc/nginx/sites-enabled
rm /etc/nginx/sites-enabled/default
# Add config variables to FastCGI environment.
echo "fastcgi_param FLOPPIES_ROOT /srv/Floppies;" >> /etc/nginx/fastcgi.conf
echo "fastcgi_param FLOPPIES_CONTAINER /tmp/floppyc.img;" >> /etc/nginx/fastcgi.conf
echo "fastcgi_param FLOPPIES_ASSETS /opt/floppcgi;" >> /etc/nginx/fastcgi.conf
# Copy the floppcgi service to /etc/systemd/system.
cp /opt/floppcgi/floppcgi.service /etc/systemd/system
systemctl start floppcgi

5 - 3. Recommendations

6. References

  1. Hardware Mods - keirf/flashfloppy Wiki
  2. Firmware Programming - keirf/flashfloppy Wiki
  3. Raspbery Pi Zero OTG Mode

Table of Contents

  1. Introduction
  2. Hardware Modification
  3. Photos
  4. Flashing and Software
  5. Floppy Server
  6. References