Fdshield

Floppy Disk Shield for Arduino UNO

Caveat and Disclaimer - Read before you build a fd-shield

• I don't own any responsibility for the data loss or physical damage on your floppy disks or computer assets caused by the use of hardware and software included in this project.
• Hardware compatibility (especially, FDD and FD-Shield compatibility) is not guaranteed. Your FDD may now work with the FD-Shield.
• The magnetic flux power on the old floppy disks are dropping and getting weak as time passes. Read-out data integrity with this system is not guaranteed.
• Recommended to use newer FDD. The old FDD may have problems on the magnetic head such as contamination, worn out or mechanical misalignment.

Announcement

23-Sep 2022 : Preview release - Feature to write back the floppy images to FD is supported. Use duplicate.py to write the *.raw floppy image data to a floopy disk. Arduino firmware update and closing JP5 on the fd-capture shield are required to enable the feature.
23-Sep 2022 : Preview release - イメージの書き戻しもできるようになりました。Arduinoファームウエアの更新とJP5ジャンパーのショートをすると書き込みができるようになります。

Description

This is a project to develop a system for preserving old 2D/2DD floppy disk data.
The system can preserve entire floppy disk data regardless whether it's normal or not. That means the system can read and preserve copy protect information in the bit-stream file as it is.
The recorded bit-stream file can be decoded and restore the contents anytime later.
The system includes a bit-stream data to D77/D88 emulator disk image converter. You can read the floppy disk with this tool and generate the disk images.
これは古い2D/2DDフロッピーディスクのデータを保存するためのシステムを作るプロジェクトです。
このシステムを使うことで仕様にのっとった正しい信号も非正規の信号も全てそのまま保存することが可能です。つまり、このシステムではコピープロテクトのための情報まで含めてビットストリームデータとして保存することが可能です。
記録されたビットストリームデータは後でデコード、解読を行うことで情報を取り出すことが可能です。
このシステムにはビットストリームデータからエミュレータ互換のイメージファイル(D77/D88)を生成するためのコンバーターも含んでいます。実際のフロッピーを読み取り、ディスクイメージを生成することが可能です。

The system consists of the hardware and software:
システムはハードウエアとソフトウエアから構成されます:

Hardware

Software

Updates

fdc_bitstream

The fdc_bitstream is my project that provides a bit-accurate C++ software FDC library. The fdc_bitstream project includes a disk image converter and image analyzer. Those software are written in C++, so they are faster than the converters in this project. Also, they are developed recently and have better algorithms for format conversion. Please try image_converter in the fdc_bitstream project as well.
fdc_bitstreamはビット精度で正確なソフトウエアFDCを開発するプロジェクトです。fdc_bitstreamプロジェクトにもイメージ変換ツールとイメージ解析ツールが含まれています。これらのツールはC++でかかれており、より高速です。またこちらのほうが開発が後なのでより良いアルゴリズムが使われており、イメージ変換の正確性も上がっています。fdc_bitstreamプロジェクトのimage_converterもお試しください。

System Diagram

FD-Shield - How It Works

Introduction of Features in the Support Tools

• bs_inspect.py
  This tool provides featurs to analyze or check the bitstream data and its quality.
  • Visualize track data including address mark and sector data occupancies.
  • Visualize data timing history.
  • Visualize data timing histogram.
  • Read all IDs in the tracks.
  • Read all sectors in the tracks.
  • MFM data dump.
  • ASCII data dump (display pritable/readable data).
  • Tweak parameters (VFO high/low gain value, sampling frequency, FDD spin speed) .

Track visualizer

You can check the address marks and sector body overlap status with this feature. The entire track data is shown in the window. The yellow vertical line indicates the position of the index hole (it appears when you capture the track data with --read_overlap option). This feature can show the decoded MFM data at the point of the mouse cursor.

• Legend:

  • Red ID : ID CRC Error
  • Green virtical line : ID AM / Index AM
  • Cyan virtical line : DAM / DDAM
  • Cyan horizontal line : Sector data (normal)
  • Magenta horizontal line : Sector data (Data CRC error)
  • Red cross mark : Record not found error
  • Yellow virtical line : Index hole
    

• Example of a normal track
  

• Example of a protected track
  

Bitstream visualizer

You can check how VFO follows the variation of pulse pitch with the bitstream visualizer.
The VFO tries to keep the data pulse be the center of the bit cell as much as possible by tweaking the oscillation frequency (= the bit cell width).

Bitstream timing histogram viewer

• Good case
• Bad case - Usually, this may be caused by the spindle speed fluctuation (that causes data pulse pitch variation in a track), or data written by multiple drives (written with drives with different spindle motor speeds).
  

Pulse (bit) pitch visualizer

You can check the pulse pitch fluctuation throughout a track with the pulse pitch visualizer. The stabler pitch, the easier MFM decode or data read.

• Stable pitch
  
• Unstable pitch. Heavily fluctuated. It's so hard to follow by the VFO. May fail data retrieving.
  

How to use (Image capture) - 使い方

1. Build Floppy shield for Arduino UNO - シールド製作

• PCB design files can be found in the ./kicad directory

2. Burn the floppy disk shield firmware (sketch) to Arduino UNO - Arduio UNOにファームウエアを書き込む
   Use fdcapture.ino
3. Assemble the system - システムを接続

• Attach a floppy shield to an Arduino UNO
• Connect a floppy shield and a floppy disk drive with a 36pin ribon cable
• Connect Arduino UNO to PC via USB cable

4. Read raw bit-stream data from a floppy disk - フロッピーからビットストリームデータを生成

• Insert a 2D floppy disk to the floppy disk drive (FDD)
• Run following command on the Windows PC:

python capture.py -o image_name.raw --read_overlap 5 [--media_type 2D|2DD]

• capture.py will search COM port for Arduino UNO and use it.
• --read_overlap option specifies how much data to read on the 2nd lap in percent.
• --media_type option specifies the media type to read. 2D or 2DD are available.
  Note: The fdcapture.ino can identify the drive type (2D or 2DD) but not the media type.

5. Convert raw bit-stream data into emulator image data (D77mod) -- ビットストリームからディスクイメージファイルを生成

python bs2d77.py -i image_name.raw --abort_id

• image_name.d77 will be generated.
  Note: The --abort_id option enables abort reading track image when the same sector ID is detected. The FD-shield can read the top of the 2nd lap with --read_overlap option. This overlapped track data may contain the same sector data twice. This option will prevent from generating the same sector in a track.

Image write back (cloning)

1. Setup the system as the same as image captureing.
   • The same fdcapture.ino firmware works for both `capture.py' and 'duplicate.y' but updating to the latest firmware is required. Use Arduino IDE to update the firmware (Arduino program).
   • Close JP5 jumper pad on the fd-capture shield.
2. Run 'duplicate.py' to write back a '*.raw' floppy image to a floppy disk.

python duplicate.py -i disk_image.raw

How to make your own FD-shield PCB (FD-shield PCBの作り方)

• PCB design data and the data for PCB manufacturing (Garber data and drill data) are included in this project. You can order your PCB at a PCB manufacturing service company. I used 'Fusion PCB' from Seeed Studio. (cost would be around $35 for 10 PCBs incl. delivery fee)
• PCB設計データとPCB製造データ(ガーバー、ドリル)はこのプロジェクトに含まれています。PCB製造サービス会社に製造を依頼してPCBを手に入れることができます。私はSeeed StudioのFusion PCBを利用しました。(10枚で4K円くらい？ 送料込み)

Accessory Tools

1. FDD spindle motor speed calibration tool
   This tool measures the index hole to index hole time and show it on the screen. You can tweak a variable register on the FDD control board to adjust the spindle speed.
   CAUTION: There might be multiple variable registers on the FDD control board. If you are unsure which one is the right one, do not turn it, or your FDD will become unfunctional.

• How to use:
  1. Set up fdcapture shield - Connect Arduino UNO, fdcapture shield, and FDD.
  2. Insert a floppy disk into the FDD.
  3. Run spindle_calibration_tool.py

Current Development Status

Done:

• Read floppy disk images (2D disk on 2D drive, 2DD disk on 2D deive, 2D disk on 2DD/2HD drive)
• Write floppy disk image to floppy disk (2D images are tested)
• Drive type auto datection (2D or 2DD/2HD)
• Drive spindle revolution measurement
• Generates D77mod disk images from the raw bitstream data (RAW->D77)
• RAW->HFE file converter
• Bit stream file quality inspection tool (bs_inspect.py)

Test Environment

• Windows 10 1909 / Windows 11 21H2
• Arduino UNO
• Floppy disk shield for Arduino
• FDDs (table below)

Addendum

FD-shield - 3D view

FD-shield - Schematics

Y1 (Xtal) = 4MHz X'tal.
U6 must be '74HCU04' (unbuffered type). The standard '74HC04' doesn't work.
The other logic ICs can be either one of '74LS' or '74HC'.
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