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Thread: A PET storage option

  1. #1
    Join Date
    Apr 2011
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    Default A PET storage option

    Hey there PET fans,

    I had some time in the last few days, and hacked up a simple drive emulator for a PET.
    It's in the breadboard stage right now, but I can save and load programs to/from a FAT32 formatted SD card attached to an Atmel ATMEGA16 microcontroller.
    It doesn't support D64 disk images, but I can load and save .prg files to the card.
    If people are interested I'll be posting schematics and source code within the next couple of days.

    Parts required are a ATMEGA16, micro-sd adapter, and a cable to connect to the IEEE-488 port on the PET: an edge connector and ribbon cable will work.

    Some pics of the project so far:
    http://www.flickr.com/photos/2521989...7626969258483/

  2. #2
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    Default

    I LIKE IT!!!

    Keep us posted!

  3. #3
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    Cool.....


    (Just got a disk drive for my pet, Still waiting on the cable and the ram/rom board so it can actually support one.)

    Later,
    dabone

  4. #4

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    And of course just today I ordered some 5 1/4 floppy disks... ;^b

    (Eh, I want to see if I can get the drives working anyway. But assuming I ever get all the bugs worked out of my PET an SD card interface would be a more practical daily driver.)

  5. #5
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    Quote Originally Posted by dabone View Post
    (Just got a disk drive for my pet, Still waiting on the cable and the ram/rom board so it can actually support one.)
    Later,
    dabone
    Ah, right, of course! You only have BASIC 1, which is why you were asking about the JB 6540 adapter; I'll dig through my notes, but you'll probably get the Welte board before I find it

  6. #6
    Join Date
    Apr 2011
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    Hi there,

    An update on the PET/SD storage device -
    I upgraded the pet disk emulator from breadboard to protoboard this weekend, and it seems to be working well.
    It supports saving and loading programs, and directory listing using "LOAD "$",8".
    There are some rough edges to iron out still, such as:
    - support for long filenames when saving a program
    - handling error conditions when files are not found (currently if you try to load a non-existent program the board goes into a waiting condition and you need to reset to escape)
    - handling multiple hardware addresses
    Currently the software doesn't pay attention to device address, and responds to LOAD/SAVE for any hardware address (8,9, etc) used by the IEEE488 port. At the moment the PETdisk just keeps NDAC low and responds to all listen/talk commands. It would be a good and relatively simple addition to specifically respond to only one hardware address. I don't have any actual PET disk drives at the moment to test this out, but I welcome someone who has the equipment to make the additions to the code..
    Schematics and code are up at:
    http://thedigitalgroup.org/petdisk
    This is a bare bones page for the moment, but perhaps I should put this up on Sourceforge?
    I welcome any comments/questions. If you are thinking about making one of these feel free to ask me any questions. I used an ATMega16 microcontroller, and for the SD card I soldered wires onto the pins of a MicroSD adapter. Pinout here: http://pinouts.ru/Memory/sdcard_pinout.shtml
    The SD card should be formatted on a computer using the FAT32 file system.
    I used code from CC Dharmani's project on interfacing an ATMega8 with an SD card: http://www.dharmanitech.com/2009/01/...ga8-fat32.html
    I added the IEEE488 interface code and added long file name support for file reads.

    Thanks for looking!

  7. #7
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    Some additional pictures of the drive emulator in action:
    http://www.flickr.com/photos/2521989...7626969258483/

    I used an empty CD-R case for a project enclosure - not much to look at but free, and convenient.
    I already had a PET edge - amphenol male cable around, so I gave this an amphenol female socket. It runs on 3.3v power, which I get from my Atmel programming board (STK500).
    Discovered another bug - seems like if too many files are in the directory, and you try to load one of the later entries in the directory, the board doesn't respond in time to the PET and I get a "file not found" error. Most likely need to speed up the file find function in the code. It's a work in progress..

  8. #8
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    Lookin' good!

    I always liked this sort of thing with a PET edge connector on one edge and pass-through fingers on the other end; no cables, no IEEE connectors, and pass-through for a printer or other drive etc.

    Great idea using a uSD adapter as a socket BTW; finally a use for them You can also pick up those multi-card USB readers for a couple of bucks these days with all sorts of card sockets.

  9. #9
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    Apr 2011
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    Thanks..
    I had a uSD with two adapters that I used for a G1 phone. Kept looking at it and wondering what to do with it, and luckily this project came around. Last I checked uSD card/adapter sets are quite cheap, and you might even have one lying around already. Hopefully the project is useful/interesting to folks here..
    For the protoboard, I used a little experimenter PCB I picked up at radio shack for a couple of bucks. Had a couple of bus lines down the middle and enough interconnects to make it useful. Made a few projects with protoboards with no copper on them, that wasn't too fun. All told, 1 microcontroller, 1 uSD adapter, 2 resistors, and a connection to the IEEE488 port.
    For power, I'm just using the 3.3v out from the STK500 programming board - but I imagine it would be possible to use the 5v output line from the PET's cassette port and regulate it down to 3.3v. Haven't tried it but thought it might be a way to make this completely self-contained without need for an external power source.
    The TX/RX lines on the ATMega16 can also be connected to a serial port for debugging, but a MAX232 or other RS232 line driver would be needed to convert to RS232 voltages.

  10. #10

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    Great project. I'll watch for further developments with interest.

    Tez
    ------------------------------------------------
    My vintage collection: https://classic-computers.org.nz/collection/
    My vintage activities blog: https://www.classic-computers.org.nz/blog/
    Twitter: @classiccomputNZ ; YouTube Videos: (click here)


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