X68KFDPI2

X68KFDPi2W

X68KFDPi2W - Floppies drive emulator All-In-One for Sharp X68000

The design is an evolution of my previous X68KFDPico, and allows the two drives of the X68000 to be emulated both externally and internally connected. The engine of the emulator are two Raspberry Pico, one ‘normal’ to handle the special floppy signals and the other ‘W’ to emulate the floppies, SDcard image management and a simple web server to choose the disks to be inserted in the floppies. Ejection and insertion of the disks can be done via the two keys in the X68KFDPi2W or by connecting the cables of the original floppy keys (in case they are not present internally). The same for the internal LEDs, which are however replicated in the emulator (only the green one, the red LED is managed only for the internal one). Floppies images format supported:

Writing to floppy images is supported: the X68000 can copy files, format disks (FORMAT) and save games to the images on the SD card. 2D/2DD (double density) images and FM sectors are not supported.

How writing works

• WRDATA is captured by a PIO state machine that measures the time between flux transitions, and a DMA channel stores them in RAM, so no write is missed while the Pico is busy (WiFi, web server).
• Core 1, which generates the read flux, watches WRGATE and records drive, side, track and the position on the track where each write starts. A normal sector write has no ID field, so the sector is found from that position; when formatting, the ID fields written by the X68000 are used.
• Core 0 decodes the MFM data with the routines of the Adafruit Floppy library (mfm_impl.h), checks the CRC, updates the track in memory (a verify read returns the new data immediately) and saves the sectors to the SD card when the write session ends (step, side or drive change, or 100ms without writes).
• Track format: a whole track is longer than the capture buffer, so the sectors not captured are filled with the same fill byte used by the X68000 (log line format: 5 sectors decoded, 3 filled with E5).
• The serial log shows one WR: line per write and per save.

Web interface

• Live status of the two drives (activity/write LED, track, R/W or read only, image format), updated every second.
• One click insert in drive 0 or 1 for every image in the folder; folders are listed first.
• "Make default" stores the full path of the image in wifi.cfg; on an empty drive it makes the drive start empty at power on (★ DEFAULT tag).
• "New disk": creates a blank, unformatted 2HD 1232KB image (.HDM or .D88) in the current folder; insert it and format it on the X68000 with FORMAT.

Options (top of X68KFDPi2W.ino)

• DEBUG_BUS (default 0): 1 prints MOTOR / DRIVE SELECT changes on the serial port (verbose).
• RESET_ON_DESELECT (default 1): the head goes back to track 0 when the drive is deselected or the motor stops. Needed by games that ask to swap disks (e.g. A-JAX).
• BUS_ON_INSERTED (default 0): READY and the bus outputs (74LVC245) are active only while an emulated drive is in use (motor on and drive selected), as in the 03/2025 release. With 1 they follow the disk inserted signals, and some games (e.g. Dracula) hang after loading Human68k.
• READY_FOLLOWS_MOTOR, DF_EN_PULLDOWN, TRK0_FOLLOWS_SELECT (default 0): experimental behaviours, off.
• READY_PULSE_ON_INSERT (default 1): when a disk is inserted (button), READY goes low for READY_PULSE_MS (50 ms). The FDC sees a READY change, as with a real drive; needed by games that wait for the new disk after an eject (e.g. Valis II).

Eject / insert controller (X68kfdPico1_11, plain Pico)

The second Pico handles the X68000 OPTION_SEL protocol (eject, lock, LED blink, disk in drive, interrupt). Version 1.10:

• The protocol runs on core 1 in a tight loop and answers an OPTION_SEL access in about 0.2 µs; buttons, LEDs and the serial log run on core 0.
• /DISK_IN_DRIVE reports the drive addressed by the last OPTION_SEL and goes HIGH (no disk) as soon as a drive that is not ours is addressed (before, drives 2/3 looked inserted).
• /INT is asserted at every disk change (eject by the X68000, button) and cleared by the next access to that drive; if it is not served it is pulsed again every 100 ms.
• The eject is ignored when the lock signal is active in the same access; buttons count only when held 30 ms.
• Options at the top of the sketch: FORCE_DRIVE01 (1 = always drives 0/1, 0 = read the INTEXT jumper), DIAG (1 = print the OPTION_SEL accesses every second), EJECT_DELAY_MS, INT_REPEAT_MS, INT_GAP_US, BUTTON_MS.
• Board: "Raspberry Pi Pico".

Valis II (original Japanese version): after the intro the game ejects disk A and waits, without any message, for the next disk (Disk D) in drive 0. Load it in drive 0 from the web page and press the insert button of drive 0.

Building the firmware

• Arduino IDE with the Raspberry Pi Pico core by Earle Philhower (tested with 6.3.x), board "Raspberry Pi Pico W".
• Libraries: Adafruit Floppy (and its dependency Adafruit BusIO); SdFat is the one included with the core.
• drive.pio.h is generated from drive.pio with pioasm drive.pio drive.pio.h (the Arduino IDE does not do it).
• logo.h contains the web page logo (from vari/logo.png).

A special thanks to Adafruit team for their great "Floppy library", from wich i starded for floppy emulation part.

NOTE Last revision fix a conflicts found when using both an internal and an external X68KFDPi2W for 4 floppy emulation, now disabled 74LVC245 when drives not enabled. Please use last PCB, X68KFDPico.u2f and X68KFDPi2W.u2f version!!

NOTE 2 Some games need tricks to properly boot, for example A-JAX works when starting with both drive off (leds off). When using 2HDboot.x for launching games from HD, you must "insert" floppy 1 & 2 pushing buttons when 2hdboot starts, then "eject" pushing again button after few seconds.

You need to add a "wifi.cfg" in root of your SDcard, with this 4 text row: SSID WIFI PASSWORD Default floppy in drive 0 Default floppy in drive 1

The 2 lines related to the default floppys can be omitted and changed everytime via Web server (a full path, e.g. /games/boot.hdm, or an empty line for an empty drive).

Gerbers file are provided for the PCB, add you pico clone, and flash the firmware ".uf2" in the Pico and in the Pico W by connecting it while pressing button on Pico and drop it in the opened windows on PC.

For any comments or questions about the projects, please use the official thread in the forum: https://nfggames.com/forum2/index.php?topic=7512.0