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GoTek Floppy Emulator, Part II - Operation

Rating: 3 votes, 5.00 average.
Okay, time to test this thing and see what's up.

As mentioned earlier, this thing comes with a mini-CD--but don't expect much. You get English and Chinese versions of the somewhat cryptic manual and a couple of software programs in RAR archives.

No installation routines; you have to figure that out all by yourself. No wonder they don't sell many of these.

The format is fixed at 18 512-byte sectors per track on 80 tracks, with sectors numbered from 1 to 18. While a format operation is accepted, it's not possible to alter the sector length or ID. If a low-density (720K) format is attempted, it won't work--you get a "sector not found". Likewise, if you try to format FM sectors, it won't work.

The USB stick appears not to have any file system on it--it's just treated as 100 1.44M blocks of data. So you can get stuff onto the USB stick by copying to it by doing a disk-to-disk copy or copying an image to the physical USB drive using DD in Linux/Unix.

So, strictly speaking, you don't need the Windows programs supplied.

Time to dig a little deeper.

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  1. tingo's Avatar
    Wow, that is worse than I expected (the "format" of the usb stick). OTOH, if we could somehow get the device to recognize other formats it would suddenly become more usable. But then we probably would need a way to "mark" the format type on the usb stick too.

    Any chance of getting at the firmware in that mcu?
  2. RickNel's Avatar
    I'm following your adventure with this. Curious whether you could boot from a floppy image via this. Also whether it is recognised by older BIOSs or recognised at all without a loaded OS. And whether images in this format can be written to original media via rawrite or dd.
  3. Chuck(G)'s Avatar
    Rick - yes, currently you can boot a floppy image, so long as it obeys the standard "DOS" 1.44/1.2MB format. As a matter of fact, AnaDisk, ImageDisk and 22Disk think it's a real floppy, so long as you stay within the high-density 512-byte sector format.

    Tingo - My next-after-the-next step is to see if I can D/L the firmware using JTAG and see if I can disassemble it. The first order of business is to buzz out the PCB and get a schematic of sorts for this.

    There should be absolutely no reason preventing us from rigging it for other sector sizes and formats. I did a similar emulator "from scratch" using SD cards and a much slower 8-bit AVR. But if there's a ready-made product that needs only new firmware to do the job, then that's going to beat any DIY project.

    So at least you know my line of thought.

    Gotek offers what amounts to the same version of this for 720K (keeps the synth people happy), so I imagine that it's just a firmware change.
  4. RickNel's Avatar
    I see there's quite a range of these (minus the Gotek brand) being sold out of Hong Kong on ebay, $25-40. Look like yours, but display digits vary between 0-3.
  5. Chuck(G)'s Avatar
    I think they're all the same basic board. Some have a USB-to-host connection, for example. The 10 pin header on the rear of the unit can connect to an external "dongle" that changes the image in use and displays the disk number. Note that the serial interface to the display (clock/data lines feeding 74HC164 shift registers connected to the displays allows for any number digits in the display.

    I strongly suspect that the major difference between any of these lies in the firmware.
  6. Chuck(G)'s Avatar
    I've started to do some probing and reading.

    That unpopulated block of 8 pads by the power connector is now making sense. The pair of pins labeled RST is just what it says--RESET when shorted. At the top end of the block, near the "J3" label we have a +3.3V supply and the BOOT0 pin from the MCU. Tying the 2 of these together causes the serial programmer to be activated after a RESET. The other pins are variously ground, and the USART1 Rx and Tx pins, as well as the SWCLK SWDIO pins for a JTAG debugger.

    So,unless the manufacturer of this thing happened to blow the "protect" fuse, we can get the firmware out (and into) this thing.

    Stay tuned...
  7. tingo's Avatar
    Following this with great interest!