USB Apple ][ disk emulator

apple

One of the most commonly frustrating things about having an old Apple ][ lying around in your basement or attic is the lack of software. While at one time in the late 80s you may have had your own copy of Oregon Trail, that disk is either lost or non-functional, and it’s pretty hard to get new disk images onto 5 1/4″ disks.

To solve this problem for himself, [Eric] came up with an Apple disk emulator. A project like this has been done many, many times over the last few decades, but [Eric] put his own twist on it: he doesn’t use a microcontroller. Instead, he used a simple USB FTDI device to talk to the Apple disk drive.

The FTDI device in question is a UM232H chip that takes a USB connection and turns it into an SPI bus. Of course the Apple ][ disk doesn’t speak SPI, so [Eric] needed to do a little logic conversion with a 74LS251 multiplexer and a 74LS161 counter.

In the video after the break, you can see [Eric] loading Apple disk images on a IIc from his new Intel Mac. It’s a neat build, but it’s not done yet: [Eric] plans on adding a microcontroller with an SD card, allowing just about every Apple ][ game every made to fit in your pocket. Yes, [Eric]’s project is quite similar to the A][ pocket serial host we saw just a bit ago, but this will hopefully have a lower component count.

13 thoughts on “USB Apple ][ disk emulator

  1. Karateka! I loved that game! So, you fight all these guys, and they get harder and harder, and you finally kill the last bad guy. You go into the next room, and there’s the princess! If you approached her in a fighting stance (default) she’d give you one quick swift kick and kill you, and you had to start over. Ha!

  2. The Apple2 has a really nice feature that lets you redirect “stdin and stdout” (the monitor and keyboard) to other controller cards in the addon slots.
    If you have a serial card in slot 2, and null-modem it to your PC, you can type: IN #2
    and keyboard input comes from both the keyboard and serial port / PC.

    There are programs such as ADTpro and a2GameServer that can send software to the apple by literally typing bytes into RAM.

    ADT (apple disk transfer) lets you read/write image files and real floppy disks.
    The ‘boot from bare metal’ option will send over a boot loader with prodos this way.

    The a2gameserver is more for sending basic or binary programs over, and specializes in sending games (obvs)

    It’s a great way to get some bootable prodos disks and even let you backup to PC all those basic programs you made.

    1. Since version 3.0, Apple Game Server can also act as a serial-based floppy drive operating at 115.2kbaud. It only supports Dos 3.3 based games though, since what it does is replace the RWTS (read/write sector) routine with a serial driver that uses the Java host as a virtual drive.

      Putting that aside, what is really impressive about this FTDI hack is that it requires precise timing to replicate exactly what a Disk II does. The apple disk controller card relies on software timing to track the disk, so if you’re off by a single cpu cycle it will fail (as you saw in his first attempt to load choplifter.) The fact he got it to work at all is just outstanding!

  3. 1. i think they make usb floppy drives if not 5.25 then 3.5 and then you can maybe get an apple 2 3.5 floppy drive

    2. that looks like a possible inspector gadget game or some karate game

    i say inspector gadget because the devil/bull horns on top of the building is dr claw’s image.

    i say karate because there was a karate game and the building looks japanese

    1. The early apple 3.5 inch disks used a variable speed mechinism making them incompatible with normal pc drives … its actually kind of a pain in the butt unless you have some old mac’s laying around

  4. Sometimes I lay in bed at night and weep because we owned an Apple ][e with at least 4 elongated disk boxes full (about 30-50 in each?) of old software, including games that when downloaded from FTP, Torrent etc., simply won’t work in an emulator without some hacking around. I could have contributed these items and made the interwebs a better place.

    But unfortunately before I became interested in preservation of digital media, we sold the Apple to some family. Now all I have are mostly “side 2″ disks of programs and old some relic instruction manuals that are already part of most ][e collections.

    1. Would you care to elaborate on why they “simply won’t work in an emulator without some hacking around”? An accurate emulator and an accurate disk dump should work just fine.

  5. shut up and take my money.
    seriously, the cffa compactflash card adapter is going for upwards of $400 on auction sites. so you could get rich selling these for any amount less than that.

    1. You can drive the serial port at 115.2 kilobaud. It’s possible to out-perform the floppy drive, especially since you can eliminate seek and spinup time completely. I think a hack like this would really be the boss in the C64 world since they are stuck with that really slow disk drive.

  6. AppleWin Works great on pc and almost ever program commecially for Apple 2 is on the web already. Put them on a usb flash drive with AppleWin you can port them to any pc.
    Mac HAs apple oasis.

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