Retronics USB Joystick Adapter and Other Coolness with V-USB

Retronics joystick adapter

There are a ton of cool gadgets available in eBay, and even though I sometimes do impulse buys, I rarely mention those in my blog. However, this extremely cool piece of retro tech is something I just cannot pass by without a comment: Retronic Design USB joystick adapter. It is essentially a joystick adapter for the popular 9-pin D-SUB connector used in many of the 80s consoles, most notably Atari, Commodore 64 and Amiga. On the outside, it’s not much to be excited about – USB connector on the one end, and grey dongle that accepts a joystick on the other. However, things quickly change when you open up the enclosure (click on the image for a large view):

Retronics USB adapter opened up

Inside the D-SUB end there is a very neat little piece of engineering, and many of my readers probably know how to program it — it isn’t anything other than a ATmega8A, a 8-bit AVR microcontroller that employs the same V-USB library I’ve covered in my tutorials to appear as a USB HID device on PC side.

All the components are on one side, and you have to admire the tiny ISP header the Retronic Design guys have fitted on the PCB. And wait, it doesn’t stop there. On the Retronic Design web site, they have full specifications for the device, and the download page includes both schematic, as well as full source code to the firmware.
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V-USB tutorial continued: HID mouse

Wow, my AVR ATtiny USB tutorial here I got featured in Hack a Day! Motivated by the influx of readers, I decided to find out how to make a USB HID (human interface device) mouse.

V-USB examples already contain an example of this, so I digged in to see what is different in usbconfig.h compared to the one we finished in my tutorial. It seems only a few things need changing:

  1. USB_CFG_HAVE_INTRIN_ENDPOINT needs to be set to have an additional endpoint
  2. USB_CFG_INTR_POLL_INTERVAL set to 100 ms instead of 10 in template
  3. USB_CFG_IMPLEMENT_FN_WRITE is not needed, nor is …FN_READ (define both to 0)
  4. Device ID and name need to be changed. I’ll just use the same ID as they did
  5. USB_CFG_DEVICE_CLASS is set to 0, not 0xff
  6. USB_CFG_INTERFACE_CLASS set to 3 instead of 0
  7. USB_CFG_HID_REPORT_DESCRIPTOR_LENGTH defined to match the structure’s length

That’s it! So here are the defines I changed:

#define USB_CFG_HAVE_INTRIN_ENDPOINT    1
#define USB_CFG_INTR_POLL_INTERVAL      100
#define USB_CFG_IMPLEMENT_FN_WRITE      0
#define USB_CFG_IMPLEMENT_FN_READ       0
#define USB_CFG_DEVICE_ID               0xe8, 0x03
#define USB_CFG_DEVICE_NAME     'M', 'o', 'u', 's', 'e'
#define USB_CFG_DEVICE_NAME_LEN 5
#define USB_CFG_DEVICE_CLASS        0
#define USB_CFG_INTERFACE_CLASS     3
#define USB_CFG_HID_REPORT_DESCRIPTOR_LENGTH    52

OK. So what about main.c? Turns out the changes are rather straightforward:
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