Amiga 500 – Gotek « modelrail.otenko

24Mar/200

Amiga 500 – Gotek

So, the goal was an internal IDE drive, but to do that I needed a boot disk as my A500 with Kickstart 1.2 would not auto-boot. To make it boot and find a HDD, I needed a floppy image written to a floppy disk. Of course, you can't write this with a standard PC drive; instead I either needed a bootable Workbench disk and serial magic (like what I did to the Apple II back in the day) to copy over floppy-copying-software, or just use a Gotek!

I happened to have a spare 'cheap' gotek that I've complained about before which deserved to be used for this hack and slashery.

Could I flash Amiga firmware to it? I don't have an FTDI USB device, but I have plenty of Arduinos! Firstly though, we'll need to allow data access to the Gotek. This means soldering on some pin-headers to the holes right behind the power plug.

Regarding using an Arduino, it's the internet, so someone has already done it. Wiring it up was pretty straight-forward: dedicate two pins to SoftSerial and then make sure the transmission line has a few resistors on it. The Gotek is TTL level, which means 3.3v data signals. As the Arduino puts out 5v, we need a 4.7k resistor between the TX pin and the gotek. Where the resistor meets your wire, also put a 10k resistor to ground.

Yup, you can't see shit because of my 'mood lighting'. The sketch on the Arduino was as follows:

#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11); // RX, TX
void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }
  mySerial.begin(9600);
}

void loop() { // run over and over
  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
  if (Serial.available()) {
    mySerial.write(Serial.read());
  }
}

Very simply, the code brings up the hardware port to 9600 baud and the same with the softserial port on pins 10 and 11. Pin 11 is TX and had the resistors, as mentioned above. The Gotek then needed 5v and GND from the Arduino. From there, you need to install the STM software and grab the Cortex hex image to flash. It's all in this blog post, with the downloads being at the very bottom.

I then unmounted the existing drive in the Amiga and swapped in the Gotek on a 3d-printed base that a friend (thanks Shouchan!) had made. Unfortunately, it seems to be for a newer revision of the A500? Or I'm mounting it wrong. Regardless, it all went in and the access light just stayed on when I booted the machine. No dice, just the usual Kickstart 1.2 screen asking for a floppy.

At this point, I could probably write a few extra paragraphs here on how I then went and tried FlashFloppy, to have that fail too. I thought I should then try HxC which also, after paying for it, ended up with the same error. So... I slept.

Testing out my 'better' Gotek

I had another Gotek (with display and buttons) that I've previously used in my IBM PCs and didn't really want to hack apart. My assumption was that the 'fake' one above with no display or buttons couldn't handle the 3rd-party firmware and this just had to work!

I did the usual... soldered on the header and programmed it.

This time I used the USB Serial adapter from Jaycar that I'd bought above to get HxC to burn. It wouldn't work via the Arduino as the baud rate needs to be 115200 and the Arduino can't 'pipe' this through quick enough! Anyway, as you can see above, I flashed it and still got the standard 'insert disk' screen. What am I doing wrong!? I then looked at the actual Gotek, which now had a beautiful error on display...

Ah crap... remember back in the day with standard floppy drives... how when you had the ribbon cable backwards, they'd just stay lit up (or even make a horrid repetitive searching noise)!? Amiga drives do this too. Better yet, when a Gotek (with a display) has the ribbon cable backwards, it'll tell you with a rib warning!

All this time spent above was a total waste as I'd just had the cable backwards the whole time. To me, the cable was actually forwards, as pin 1 matched pin 1 on both ends... but it turns out you need to flip it on the Gotek side. I'm sure this information is written in a manual somewhere?

A quick flip of the cable and...

Hoy polloy... I've learnt a lot... have a bit of new usb-serial hardware, and two dismantled Goteks. So, I then purchased the original Workbench disks from Amiga Forever (USD$9.95 for just the floppy images!) and threw the ADFs on the USB drive.