https://github.com/gblargg/vusb-joystick

Minimal USB joystick example using V-USB
https://github.com/gblargg/vusb-joystick

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Minimal USB joystick example using V-USB

• Host: GitHub
• URL: https://github.com/gblargg/vusb-joystick
• Owner: gblargg
• License: other
• Created: 2014-06-19T06:51:32.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2014-07-07T06:52:17.000Z (over 10 years ago)
• Last Synced: 2024-08-03T09:02:09.928Z (4 months ago)
• Language: Assembly
• Size: 242 KB
• Stars: 21
• Watchers: 5
• Forks: 15
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: License.txt

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README

        
V-USB Joystick Example

======================

This uses V-USB to implement a USB joystick with minimal code. It supports up, down, left, right and two buttons (and can trivially handle 6 more).

The code runs on Thomas Fischl's 12MHz atmega8 USBasp programmer hardware, which supports V-USB, has several I/O pins, and is available cheaply. It can be programmed using a second USBasp programmer or by loading something like USBaspLoader on it to allow self-reprogramming.

I wrote this example because none of the other joystick projects I found implemented just a simple joystick with a minimal amount of code. I was able to pare this example down to very little code so that the essence is easier to understand. Thanks to others whose joystick allowed me to write this.

Files

-----

	main.c          USB joystick

	usbconfig.h     Configures V-USB

	usbdrv/         Software-based USB driver; see http://www.obdev.at/vusb/

	Makefile        Compiles code and flashes it

	README          This documentation

	License.txt     GPL v2 + V-USB additions

	schematic.png   Schematic of USBasp hardware

	usbasp.jpg      USBasp hardware this was tested on

Building

--------

* Use second USBasp programmer to reprogram first. Connect them together via ISP ribbon cable. Close JP2 on first one to allow reprogramming its firmware. Connect second one to USB.

* Build and flash firmware:

	make flash

* Disconnect second programmer from USB and ISP ribbon.

* Plug first one into USB and verify that it shows up as joystick.

* Run a joystick test program that shows what's being pressed. On Linux:

	jstest --event /dev/input/js0

* Connect GND to one of the control pins and verify that button presses show up (be sure to avoid connecting it to +5V!). LED should toggle between on and off each time you close/open a button pin.

Hardware

--------

Controls (connect to GND to press):

		       ------

	 Down PB3 | 1  2 | +5V

		  N/C | 3  4 | PD1 Button 1

	   Up PB2   5  6 | PD0 Button 0

	Right PB5 | 7  8 | GND

	 Left PB4 | 9 10 | GND

		      ------

	Male connector on USBasp programmer

Operation

---------

V-USB implements a low-speed USB device in software. When connected, it tells the host that it's a USB joystick. It also tells the host what controls it has and the format of the report it sends (usbHidReportDescriptor[] in main.c). Then when the joystick changes it sends the new state of the controls to the host. This can only be done every 8ms (1/125 second), when the host asks the device if it has any updates. There are ways to make the host check more often (up to 1000 times a second) by changing its hid polling rate.

-- 

Shay Green