Pocket Serial Host acts as an Apple II disk drive


[Osgeld] is showing off what he calls a sanity check. It’s the first non-breadboard version of his Pocket Serial Host. He’s been working on the project as a way to simplify getting programs onto the Apple II he has on his “retro bench”. When plugged in, the computer sees it as a disk drive.

The storage is provided by an SD card which is hidden on the underside of that protoboard. This makes it dead simple to hack away at your programs using a modern computer, then transfer them over to the retro hardware. The components used (starting at the far side of the board) are a DB9 serial connector next to a level converter to make it talk to the ATmega328 chip being pointed at with a tool. The chip below that is a level converter to get the microcontroller talking to the RTC chip seen to the right. The battery keeps that clock running when there’s no power from the 5V and 3.3V regulators mounted in the upper right.

The video after the break shows off this prototype, the breadboard circuit, and a demonstration with the Apple II.

[Thanks Brendan]


  1. Willaim says:

    Very Nice awesome Work

  2. Awesome stuff! Thanks for the demo video — it really shows off the speed of this thing — the Apple II Desktop is not a small app by any means!

  3. Mike Skoczen says:

    I agree with William good job but
    The first Apple II computers 1 MHz, 4 KB of RAM
    atmega328 20 MHz 32 Kbytes flash
    Just had to make the comparison your adapter is more a more powerful computer than what is it connecting to.

  4. osgeld says:

    Well, hello HAD, been a while.
    I just wanted to make note that the software running on the Apple II was written by David Schmidt, based on previous work done by Terence J. Boldt … I just did a port for AVR

  5. Dissy says:

    Wow, that is a nice piece of kit!
    The a2 was my first computer and will always have that special place. a2 posts are too far and in between, thank you for this.

    I’ve been using a CFFA3000 for this purpose, but it’s a closed product and not too hackable.
    I’ve never been able to wrap my head around the low level disk controller protocols to design such a thing myself.
    It was amazing what Woz could do in software for sure, but talk about complicated ;}

  6. Galane says:

    DE9. The B size D-subminiature (sub-miniature compared to the honking big connectors before them) is what’s used for 25 pin parallel and serial connectors and weird things like DB13W3 SUN monitor connections.

  7. Pavel says:

    Would it work with Apple][e same way?

  8. Steve says:

    nifty! I always have problems with memory issues when loading programs with adt

  9. Petiepooo says:

    Why the RTC chip?

  10. Timinator01 says:

    Would somthing like this work with a IIGS one poped up under a sink in my high school and my friend and i have been meaning to get an operating system running on it rather than just using apple BASIC (or whatever the command line on it is called) but we dont have any disks for it just a 4.5 inch drive and a borked 3.5 inch drive

    • osgeld says:

      yes, the disk image that comes with ADT fits on a 140k 5.25 inch floppy, though I dont know how compatible it is with running GSOS off the SD card, I dont have one to try.

      I know the 8 bit desktop runs, but its more or less a shell launcher, and on the other side of that geos will crash as of right now cause it overwrites the driver in ram

  11. vonskippy says:

    Great tech, but come on, an Apple II is boat anchor material.

  12. Pavel says:

    Its posssible also saving data back to SD card???

  13. Jose Gregorio says:

    I was thinking of doing something similar with my 5 apples. My question is … are for sale? and yes, what is the price and where I can buy.

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