Atari ST/STe for MEGA65 (MegaST)

This is a port of the AtariST_MiSTer core (the "MiSTery" Atari ST/STe core by Till Harbaum, Gyorgy Szombathelyi, Jorge Cwik, Alexey Melnikov and others) to the MEGA65, using the MiSTer2MEGA65 framework. MEGA65 port by Chris Freeman (@freemchr).

Status: stable, running on real hardware. MegaST is developed and tested on a MEGA65 R6 and runs games and GEM programs from floppy and hard disk images. Download the core from Releases; see below for what has been tested on the MEGA65. Please report problems and successes in the issues.

Latest version: 1.1.4 (October 22, 2026): no more bombs after a reset (mostly STEroids), a cartridge can be removed (Space on the "Cartridge:" line), and no more coloured stripes behind the welcome screen (all tester reports, tested on an R6). 1.1.3 fixed the monochrome flicker on HDMI at 720p. Since 1.1 (October 16, 2026) the MEGA65's internal floppy drive works as the ST's drive A: (read only, issue #15, see Real floppy drive). Original ST disks, including copy protected games with 10 sectors and 82 tracks, are read as on a real ST. Core files for the R3/R3A and R6 (from 1.1.4 on there are no separate R4 and R5 files; if you have one of these boards, please open an issue). Coming from 1.0 or older: copy the new atarist/stcfg (104 bytes) from the zip, otherwise the menu settings are not saved (from 1.1 on, keep your file). All versions up to 0.4.10 damage hard disk images when writing (issue #11): if you wrote to an image with one of them, restore it from a backup.

Support: MegaST is free and open source. If you enjoy it, you can support its development via Buy Me a Coffee or GitHub Sponsors.

Tested on a MEGA65 R6

Area	Result
TOS 1.04, boot to the desktop	works
TOS 2.06 (STe) and EmuTOS 1.4, boot and hard disk	work (tester reports)
TOS 1.62 (STe, 1 MB)	works (tester report, issue #21)
TOS 1.00, 1.02, 1.06	boot to the desktop in simulation, not tried on hardware yet
Floppy disks: loading, changing disks, reset with a disk inserted, saving	works
Hard disk: 4 GB .vhd image (MiSTer image), boot, reading files, launching programs	works
Hard disk: writing files	broken up to 0.4.10, works since 0.4.11 (tester report, issue #11)
Remembered disk images restored at power-on	broken in 0.4.12/0.4.13, works since 0.4.14 (tester reports, issues #11, #12)
MEGA65 keyboard, all keys (A fixed in 0.4.7), numeric keypad via MEGA	works
Atari ST mouse, in port 1 or port 2	works; right button as a short click only (see Usage, issue #17)
Amiga mouse (optical, incl. right button), in port 1 or port 2	works
mouSTer USB adapter, firmware 3.23.5313, Amiga or 1351 mode (see Usage)	works (tester report, issue #17)
Joystick, with debouncing for bouncing and worn switches (Suncom TAC-2)	works
Menu settings saved on the SD card (stcfg)	works
VGA scanlines, full borders	works
HDMI picture centred, not cut off on the right (576p, 720x480, 640x480)	works (since 1.0)
Internal floppy drive as A: (original Jim Power disk: boot, game)	works (since 1.1); R3-R5 not tested with the drive
Internal floppy drive with EmuTOS (drive A: on the desktop)	works since 1.1.1 (no drive icons in 1.1, issue #24); R3-R5 not tested with the drive
Games: Golden Axe, Great Giana Sisters, Turrican	work
Games: Buggy Boy, Goldrunner, Goldrunner II, The Hitchhiker's Guide to the Galaxy, Lemmings	work (tester report, issue #21)
Cartridges, PMOD serial/MIDI/printer, Cubase dongles, Viking card, mono monitor	not tested yet
1351 mouse	works (tester report on the R3, issue #22)
HDMI "DVI mode (no sound)" with a DVI monitor	works (tester report, issue #4)
R3 and R3A boards (CORE-R3.xpr, 512 KB)	work, including hard disk images (tester reports, issues #2, #22)
R4/R5 boards (CORE-R4.xpr, CORE-R5.xpr)	not tested yet

Screenshots

TOS 1.04 desktop	EmuTOS 1.4 (included in the release zip)

(Frames from the simulation of the core, i.e. the exact picture the core generates, before the HDMI scaling.)

Features

• Atari ST, STe, Mega STe (16 MHz) and "STEroids" modes
• 512 KB, 1 MB, 2 MB, 4 MB, 8 MB and 14 MB of ST RAM
• Blitter (always on in STe mode, optional in ST mode)
• All TOS versions: 192k TOS (1.00 - 1.04), 256k TOS (1.06, 1.62, 2.06) and EmuTOS; tos.img is loaded at power on, another TOS image can be loaded from the menu
• Two floppy drives (.st images, read/write), can be swapped (boot from B:); blank disk images can be created with tools/make_st_disk.py
• The MEGA65's internal 3.5" drive as drive A: (real DD disks, read only)
• Two ACSI hard disks (.hd/.img/.vhd images, read/write, directly on the SD card, up to 4 GB)
• ROM cartridges (raw .img or .stc, up to 128 kB)
• Viking/SM194 compatible 1280x1024 monochrome card (shown as 640x512 grey scale)
• Serial port (RS232), MIDI and parallel (printer) port on the MEGA65's PMOD headers
• Color (low/medium resolution, 50/60 Hz) and monochrome (SM124, 71 Hz or 60 Hz) monitor, normal or full borders (overscan)
• YM2149 and STe DMA sound
• Real IKBD (HD6301) with the MEGA65 keyboard mapped directly into the ST keyboard matrix, numeric keypad via the MEGA key
• Mega ST real time clock (RP5C15), set from the MEGA65's real time clock
• Atari ST mouse, Amiga mouse, Commodore 1351 mouse or mouSTer USB adapter in MEGA65 joystick port 1 or 2 (menu "Controllers & ports"), joystick in the other port, STe enhanced joystick ports (fire button only)
• Cubase 2 and Cubase 3 dongle in the cartridge port
• HDMI (720p/576p/480p/600p) and VGA output: 31 kHz (optionally with scanlines) or 15 kHz RGB (optionally with composite sync, e.g. for SCART), zoom-in without the border

Requirements

• MEGA65 R3, R3A, R4, R5 or R6 board. On the R4-R6 the ST RAM is in the SDRAM (up to 14 MB). The R3/R3A has no SDRAM, and its HyperRAM is too slow for the ST's cycle exact memory timing, so its own core (MegaST-R3-...cor) keeps the ST RAM in the FPGA's block RAM: 512 KB ST RAM, no Viking card and no STEroids mode, everything else is the same.
• SD card with a folder /atarist containing
  • tos.img: your TOS image (mandatory). The release zip contains the free EmuTOS as tos.img; a TOS ROM dump of your own Atari also works.
  • your floppy disk images (.st), hard disk images (.hd, .img, .vhd) and cartridges (.stc, .img)
  • optionally stcfg, an empty settings file, if you want the menu settings to be saved (included in the release zip, or cd M2M/tools && ./make_config.sh stcfg auto). The file must have exactly as many bytes as the menu has lines (OPTM_SIZE in CORE/vhdl/config.vhd, currently 104). When the menu changes in a new release, a settings file of the old size is ignored: use the new one.
  • optionally stmount, if the core shall remember the mounted floppy and hard disk images and the TOS and cartridge chosen in the menu (included in the release zip). It must have exactly 1536 bytes, all 0x00 or all 0xFF (e.g. python3 -c "open('stmount','wb').write(bytes(1536))").

Usage

• Press Help to open the on-screen menu: mount floppy disks, choose the machine type, memory size, video output and more. "Reset Atari ST" resets the ST (like the reset button of the MEGA65, the ST RAM is kept).

• With /atarist/stmount on the SD card (see Requirements), the core remembers the images you mounted and the TOS and cartridge you chose, and loads them again at the next start, before the ST boots (so a hard disk is found and the right TOS starts). To unmount (eject) a drive, select its line in the menu and press Space; this also forgets it. A drive that still has unsaved writes stays mounted until they are written to the SD card (a few seconds). A long press of the reset button restarts the core like a power cycle, so the remembered images come back; unmount them in the menu if you want empty drives. An image that is no longer on the SD card is skipped. In "System settings", "Remember floppies" and "Remember TOS/cartridge" (both on by default) decide whether the floppies and the TOS and cartridge come back at the next start; when off, the drives start empty and tos.img is used. Hard disks are always remembered.

• Keyboard mapping (the MEGA65 has a C64 style layout, symbols are mapped by position):

  MEGA65	Atari ST
  F1, F3, F5, F7, F9	F1, F3, F5, F7, F9
  Shift + F1 .. F9	F2, F4, F6, F8, F10
  MEGA + F1 .. F9 (with or without Shift, since 1.0)	Shift + F1 .. F10 (F11 .. F20 in GFA-Basic, STOS)
  F11, Run/Stop	Undo
  F13	Help
  Inst/Del	Backspace
  Arrow up (↑)	Delete
  No Scroll	Insert
  Clr/Home	Clr/Home
  Ctrl, Alt, Esc, Tab	Control, Alternate, Esc, Tab
  Caps Lock	Caps Lock
  + - £	- = \
  @ * ←	[ ] `
  : ; =	; ' ISO key (<>)

• Numeric keypad: hold the MEGA key. MEGA + 0..9, +, -, *, /, . and Return are the keypad keys, MEGA + Shift + 8 / 9 are the keypad keys ( and ).

• Keyboard "as printed" (0.4.8, "Controllers & ports" → "Keyboard", issue #6): digits and symbols give the character printed on the MEGA65 key instead of the ST key at the same position, e.g. Shift + 2 is ", + is +, @ is @, : is :. The ST's own layout depends on the language of the TOS, so choose "As printed, US TOS" or "As printed, UK TOS" (the EmuTOS in the release zip is UK). Other TOS languages: use "ST keys (positional)", the default. Characters that are not printed on the MEGA65:

  MEGA65	Atari ST
  Shift + : / ;	[ / ]
  Shift + @ / *	{ / }
  £, Shift + £	\, |
  Shift + -	_
  ←, Shift + ←	`, ~

  Keys without a shifted symbol on the MEGA65 (0, +, =, ↑) give the same character with Shift.

• Mouse: an Atari ST mouse works out of the box. For an Amiga mouse (or a mouSTer in Amiga mode) or a Commodore 1351 mouse, select it first in the menu: "Controllers & ports" → "Mouse type" → Amiga / 1351. With the wrong mouse type, an Amiga mouse only jitters in small steps. "Mouse port" selects the MEGA65 port the mouse is plugged into (default: port 1); the joystick goes into the other port. The right button is read from pin 9, which has no pull-up on the MEGA65, so an open pin looks like a pressed button. The core therefore ignores the right button until it has seen pin 9 released. An adapter that leaves pin 9 open (or a joystick in the mouse port) gets no right button, but it no longer holds it down.

• Right button of an Atari ST mouse: the Atari mouse does not pull pin 9 up either (on the ST the mainboard does). Its button only grounds the pin, and after a release the open line takes about 10-13 seconds to float back up (measured on an R6; 2-6 seconds on a tester's board). The core can not see the release, so with Mouse type = Atari a right click counts as a short click (200 ms): right-click menus work, but holding the right button (dragging, drawing) does not, and a second right click only counts once the line has floated back up (about 10 seconds later).

• mouSTer (USB mouse adapter): the mouSTer emulates a real mouse so closely that its right button has the same pull-up problem: it sticks after the first click. With mouSTer firmware 3.23.5313 or newer, these two setups work (tester report, issue #17):

  Core "Mouse type"	mouSTer INI
  Amiga	[mouster] mode=auto (or mouse), [mouse] type=amiga, activepotlines=true
  1351	[mouster] mode=mouse, [mouse] type=c1351, activepotlines=false

  With activepotlines=true the mouSTer drives the right button line itself (the same setting the MEGA65 Amiga core needs).

Using disk images

The menu and the file browser

• Help opens and closes the menu. Cursor up/down moves, Return selects.
• Selecting "Floppy A:", "Floppy B:", "Hard disk 0:", "Hard disk 1:", "TOS:" or "Cartridge:" opens the file browser in /atarist. Cursor up/down selects a file, cursor left/right turns the page, Return opens a folder or mounts the file, Run/Stop cancels. F1 / F3 switch between the internal and the external SD card.
• The browser only shows the file types the core can use: .st (floppy), .hd, .img, .vhd (hard disk), .img, .rom (TOS), .stc, .img (cartridge).
• The menu shows the name of the mounted image next to the drive. To unmount (eject) a drive, select its line and press Space. The same on the "Cartridge:" line removes the cartridge: the ST restarts without it.
• With /atarist/stmount on the SD card (in the release zip), the mounted images and the chosen TOS and cartridge are remembered and loaded again at the next start ("Remember floppies" and "Remember TOS/cartridge" in "System settings" switch this off for the floppies or the TOS).

Floppy disk images

1. Copy the .st image into /atarist on the SD card (or into a subfolder).
2. Press Help, select "Floppy A:" and choose the image.
3. To boot from it (most games): select "Reset Atari ST" in the menu, or switch the MEGA65 off and on with stmount on the SD card. A disk mounted while the ST is running is seen like a real disk change, e.g. to open it on the desktop.
4. Disk changes: when a game asks for disk 2, mount disk 2 on "Floppy A:" (no reset).
5. Saving: the ST writes into a copy in memory; about 2 seconds after the last write the core writes the image back to the SD card. The drive LED is yellow until that is done: don't switch off or remove the SD card while it is yellow. "Write protect floppies" (System settings) protects the images; "Swap floppy A: and B:" boots from the disk in B:.
6. New empty disk (e.g. for game saves): python3 tools/make_st_disk.py blank.st on your computer (see Floppy disks).

Hard disk images

1. Copy the image (.hd, .img or .vhd, up to 4 GB) into /atarist on the SD card.
2. Press Help, select "Hard disk 0:" and choose the image. Large images show "Scanning disk image..." for a moment.
3. Reset the ST ("Reset Atari ST" in the menu). TOS only looks for hard disks when it starts, so a hard disk mounted while the desktop is shown does not appear without a reset. With stmount the image is mounted at power on before the ST starts, so no reset is needed.
4. With EmuTOS, drive C: appears on the desktop by itself. With Atari TOS, the hard disk driver on the image (HDDRIVER, AHDI, ICD, ...) starts first and adds drive C:. If there is no C: icon, add it once with "Options" → "Install Disk Drive" (TOS 1.x) or "Install Icon" (TOS 2.06), then "Save Desktop".
5. Hard disk writes go straight to the SD card (no delay). The drive LED is red while the ST accesses the hard disk.

More about images, drivers and Hatari images: Hard disks.

FAQ

My image is not in the file browser. Only .st, .hd, .img, .vhd, .rom and .stc files are shown. .msa and .stx floppy images and .zip files are not supported: unzip them on your computer and convert .msa to .st (e.g. with Hatari's hmsa tool: hmsa game.msa writes game.st). .stx (Pasti, copy protected originals) cannot be converted.

The hard disk is mounted, but there is no drive C:. Reset the ST after mounting (see above). With Atari TOS the image needs a bootable hard disk driver, and a C: icon on the desktop. A quick test: boot the EmuTOS from the release zip. If EmuTOS shows C:, the image works and the problem is the driver or the desktop setup. (0.4.12 and 0.4.13 ejected a hard disk image restored at power-on again inside the core, so TOS did not see it; fixed in 0.4.14, issues #11 and #12.)

The game does not start from the floppy. Mount the disk on "Floppy A:" and reset the ST. Some games need a real Atari TOS (TOS 1.02 or 1.04 for the ST, see TOS), some need 512 KB or 1 MB of memory or the ST (not STe) machine type. A few images in circulation are defective, see Game notes.

Are my saves on the floppy kept? Yes, if the image is not write protected: wait until the drive LED is no longer yellow before switching off.

How do I get empty drives at the next start? Unmount the drives with Space in the menu. Without /atarist/stmount on the SD card, all drives start empty anyway.

Some games of a hard disk game collection don't start. Most hard disk versions of games need 1 MB of ST RAM or more (512 KB is often not enough, e.g. on the R3/R3A), and some only work with certain TOS versions. If a game fails, try more RAM and another TOS, and compare with Hatari using the same image and TOS.

Can I use a folder of my PC as drive C: like in Hatari? No, that is an emulator feature ("GEMDOS drive"). The core needs a hard disk image, like a real ST.

TOS

/atarist/tos.img is loaded at power on. "TOS" in the menu loads another TOS image (.img or .rom) and restarts the ST with it (cold boot). With /atarist/stmount on the SD card (in the release zip), this choice is remembered and the chosen TOS is loaded again at the next start. Without stmount, tos.img is used again after a power cycle. STe and Mega STe modes need TOS 1.06 or newer (or EmuTOS).

Mega STe speed: like a real Mega STE, the Mega STe mode starts at 8 MHz with the cache off; TOS 2.06 does not switch it. Set 16 MHz and the cache in the XControl "General" panel (or with a speed utility). "STEroids" always runs at full speed and has no speed setting; tools that only know the real Atari models cannot measure it.

Which TOS? EmuTOS is in the release zip only because it is free and may be distributed (Atari's TOS may not). It is fine for GEM programs and for a first test, but some games crash with it. For games, use a real Atari TOS: TOS 1.02 or 1.04 for the ST (some games only run reliably with TOS 1.02), TOS 1.62 or 2.06 for the STe. Use a ROM image dumped from your own Atari.

TOS 1.06 and 1.62 start slowly: after a cold boot without a hard disk, the screen stays white for about 14 seconds (measured in the simulator) before the desktop appears. The TOS boot code waits for a hard disk on the ACSI bus; the ST has not hung.

Changing the memory size or the machine type: since 0.4.8 the ST restarts with a cold boot by itself (issue #7). In 0.4.7 and older it did not boot after such a change, because TOS keeps the old memory layout in RAM and trusts it at the next reset: load a TOS with "TOS" in the menu (or switch the MEGA65 off and on) after the change.

Real time clock

The ST has the clock chip of the Mega ST (Ricoh RP5C15 at $FFFC21), which TOS 1.02 and newer and EmuTOS use automatically. It shows the time of the MEGA65's real time clock: set the clock in the MEGA65 configuration utility. Setting the time on the ST (e.g. in the control panel) does not change the MEGA65 clock and is overwritten by it.

Hard disks

The hard disks are ACSI targets 0 and 1. The images are raw disk images (as used by Hatari, MiSTer and MiST; .hd, .img or .vhd like on MiSTer, but not a Microsoft "dynamic" VHD), e.g. with a DOS (MBR) or Atari (AHDI) partition table. Images can be almost 4 GB large (the limit of FAT32); disks larger than 1 GB need a driver with ICD commands (EmuTOS, HDDRIVER). EmuTOS finds the partitions automatically; with Atari TOS you need a hard disk driver (AHDI, HDDRIVER, ...), e.g. on a boot floppy or on the hard disk itself.

How to use a hard disk image: see Hard disk images above.

Images that work in Hatari do not always work here:

• Hatari often uses a PC folder as drive C: ("GEMDOS drive"). That needs no driver and no image at all, so it works with any TOS. A real ST, and MegaST, needs a hard disk image with a driver.
• Hatari also emulates IDE and SCSI disks. The ST and STe only have ACSI; the image must be prepared for an ACSI disk (HDDRIVER and AHDI images usually are).
• An image without a bootable driver (e.g. created by Hatari's atari-hd-image tool, which writes a DOS partition table and no driver) works with EmuTOS, but with Atari TOS only together with a driver from a boot floppy.

A first test: if EmuTOS shows drive C: for the image, the image and the ACSI disk work, and any problem with Atari TOS is in the driver setup.

The images are not loaded into RAM: every sector is read from and written to the SD card directly (write-through). The FAT32 library of the framework can only seek from the start of a file, following the cluster chain; the firmware therefore remembers the cluster of every 2 MB of an image (4 MB for images larger than 1 GB, 8 MB above 2 GB) and seeks from there or from the current position (see M2M/rom/vd_fastseek.asm), so random access is fast in large images, too.

Floppy disks

The floppy disk images (.st, 360 kB to 1.44 MB) are loaded into the HyperRAM and written back to the SD card when the ST writes to them. "Swap floppy A: and B:" in the system settings exchanges the drives, e.g. to boot from the disk in B:.

To create an empty, formatted disk (e.g. a save disk for a game), run python3 tools/make_st_disk.py blank.st on your computer (options: --size 360|720|800|1440, --label NAME) and copy the image into /atarist on the SD card. (The FDC emulation cannot format a disk, so formatting a disk image in TOS does not work.)

Real floppy drive

Since 1.1 the ST can use the MEGA65's internal 3.5" drive as drive A:. Switch on "Real floppy drive as A:" in "System settings" and choose "Reset Atari ST". Drive A: is then the disk in the MEGA65's drive; drive B: and the floppy images are not used until you switch it off again. With EmuTOS this needs 1.1.1 or newer (1.1 showed no drive icons, issue #24). Up to 1.1.1 a reset took 5 to 10 seconds longer while the real drive was on (TOS waited for the missing drive B:); fixed in 1.1.2. With no disk in the drive, TOS still waits a moment for drive A:. Original ST disks are read as on a real ST: the core has a complete WD1772 floppy controller (WF1772IP by Wolfgang Förster), so copy protections and formats with 10 or 11 sectors and more than 80 tracks work.

• Read only: the core never writes to the disk. Programs that save to the disk (high scores, save games) get an error.
• DD disks only (the 720 KB type). HD disks are not supported.
• "Floppy read assist" (System settings, on by default): the MEGA65 drive's speed varies within each turn of the disk, more than an Atari drive's, and the WD1772 then misreads a sector now and then. Some loaders hang on such an error. With read assist the core cleans up the timing of the drive's signal and re-reads a sector that failed its checksum (up to 15 more turns) before the ST gets it. Switch it off only to compare.
• Weak disks: a disk that reads fine in a PC drive can still have weak spots. If a disk does not load, try it in a real ST or make a fresh copy (e.g. with a Greaseweazle) and report it in issue #15, with the board, the disk and the program.

Game notes

Tester reports about single games and disk images. Please report others in the issues, with the name and MD5 of the image.

Game / image	Note
Road Blasters (1988)(U.S. Gold).st (TOSEC, MD5 f3afdf00840c7e91b48d6b3daf8a4daf)	Defective image, also misbehaves in Hatari: no joystick control, and after a reset a long write back to the SD card (issues #8, #9). Use a different dump.
Gauntlet	Works; press Insert (MEGA65 No Scroll) to start the game (issue #9).

Video

• HDMI: the image is scaled by ascal (4:3, with the border). "Zoom-in (hide border)" shows only the graphics area (320x200, 640x200 or 640x400) and uses the full width of 16:9 modes. The border is black on VGA in this mode.
• DVI monitors (HDMI-to-DVI cable or adapter): if the picture is garbled, enable "DVI mode (no sound)" in the HDMI settings. It switches off the HDMI audio and info packets that DVI monitors cannot decode. If the menu is unreadable on the DVI monitor, change the setting while a VGA monitor is connected (the setting is saved), or try a lower HDMI mode such as 800x600.
• VGA: the color modes are 15 kHz modes. By default they are doubled to 31 kHz for VGA monitors ("VGA: 31 kHz"), optionally with scanlines (25%, 50%, 75%). "15 kHz (RGB, SCART)" outputs the original 15 kHz signal for CRTs and TVs, "15 kHz with CSync" puts composite sync on the HSync pin (for MiSTer style VGA-to-SCART cables). The monochrome mode is output unchanged with the original SM124 timing (640x400, 71.2 Hz, 35.7 kHz), so the VGA monitor must accept that mode. "Mono 60 Hz" adds blank lines to get ~60 Hz (same 35.7 kHz line rate).
• HDMI and the 71 Hz mono mode: the HDMI output always runs at the HDMI mode's rate (50 or 60 Hz). ascal writes the 71 Hz frames into its frame buffer and reads them at the output rate, so some frames are dropped (about 1 in 6 at 60 Hz). Since 1.1.3 the frame buffer has 16 bits per pixel and three buffers: no flicker at 720p and no tear line. For smooth motion, enable "Mono 60 Hz" and use a 60 Hz HDMI mode.

Viking/SM194 card

Enable "Viking 1280x1024 card" in the system settings and load a Viking driver (memory must be 8 MB or less, the card uses $C00000). As soon as the driver accesses the card, the video output switches to the card. The MEGA65's video pipeline cannot handle 1280x1024 at 96 MHz, so 2x2 pixels are averaged into one of five grey levels: 640x512 @ 60 Hz, 31 kHz.

PMOD headers (serial port, MIDI, printer)

When "PMOD: RS232/MIDI/printer" is enabled in the "Controllers & ports" menu, the PMOD headers are powered and used as follows (3.3V TTL levels, all inputs have pull-ups):

Pin	Signal	Pin	Signal
PMOD1 lo[0]	RS232 CTS (in)	PMOD1 hi[0]	MIDI OUT (out)
PMOD1 lo[1]	RS232 TXD (out)	PMOD1 hi[1]	MIDI IN (in)
PMOD1 lo[2]	RS232 RXD (in)	PMOD1 hi[2]	printer STROBE (out)
PMOD1 lo[3]	RS232 RTS (out)	PMOD1 hi[3]	printer BUSY (in)
PMOD2 lo[0..3]	printer D0..D3 (in/out)	PMOD2 hi[0..3]	printer D4..D7 (in/out)

PMOD1 lo matches the Digilent PMOD UART pinout (e.g. a PmodUSBUART or a MAX3232 module). MIDI needs the usual opto-coupler (IN) and driver (OUT) circuit. The parallel port pins also allow "Gauntlet" style joystick adapters.

MT32-pi: the MT32-pi reads serial MIDI with 3.3V levels on the GPIO UART of the Raspberry Pi (midi_in = gpio or the default configuration of the MT32-pi with a GPIO MIDI connection), so it can be connected without any MIDI circuit: PMOD1 hi[0] (MIDI OUT) to the RXD pin of the Pi (GPIO 15) and GND to GND. Its sound comes from the audio output of the Pi. (On MiSTer the MT32-pi audio is mixed into the core via I2S; this is not supported.)

Not supported (yet)

• Ethernec, MT32-pi audio mixing (MIDI to an MT32-pi works, see above)
• Jaguar pad buttons beyond fire on the STe joystick ports (the MEGA65 joysticks have one button)

Building and development

How the port works, the source files, the changes to the MiSTer core, the tests and how to build the core: see doc/DEVELOPMENT.md.

License

GPL v3, see LICENSE. The MiSTer core is licensed under GPL v2 or later (FX68K: GPL v3). TOS is copyrighted by Atari and is not part of this repository.