USB programming

Question

I want to program a microcontroller (AVR) to control some leds through USB. It\'s just out of interest in how to build and program USB devices. There are some AVR microcontrolle

Answer 1

That sounds like a great project! I'd suggest starting off with something a little simpler since you're - as you say - a "total n00b". I'm not sure what hardware you currently have (or have in mind) but what I would suggest for the total beginner is the STK500. It's a development board that's very well supported in both Linux and Windows and will give you the most flexibility. It comes with LEDs and switches built in for your projects, but you will need to get a microcontroller. And for that I recommend the ATMega32, a great multi-purpose IC that's also well supported and has lots of documentation on the web.

Once you get those I suggest you do your development on Linux using avr-gcc (make sure to also install avr-libc). If you're using Ubuntu it's easy to get all the packages you need:

% sudo apt-get install gcc-avr avr-libc avrdude

Those should get you up and running. I'd suggest Googling around for help writing your first programs but another good resource is the online materials for this class at Cornell.

That's enough to get your feet wet with AVR microcontrollers and the development tools. The sky is the limit at that point but since you said you want to get into USB I'd suggest using the excellent V-USB framework to have your ATMega32 act as a USB device. After that, as they say, the steps to flipping LEDs are a piece of cake :).

Answer 2

One good way to go is just to develop a HID device, since the driver is built in to most higher level OSes and pretty flexible for simple IO like you are talking about. Another good option is just using a USB RS232 device or software. I use PICs which have a number of nice devices with USB onboard.

Answer 3

I created a USB-keyboard adapter last year for my capstone. I did not do the host programming but used existing code that you can find on the web.But I did program the device side and for that I got a lot of help from this website Teensy Look into their "Code Library" which has code for Keyboard, Mouse and others. Also, the USB protocol handbook will always be useful and you should always consult it when you are doing stuff with USB.

Answer 4

I wonder whether your AVB acts as a host or device. I guess your board is a usb device and you need to light the leds on your board. So, it may be a good way to initialize your board as a HID device. To achieve this goal, you need a HID gadget software stack running on your board. References as follows:

1. gadget framework in uboot
2. HID specefication usb org
3. debug tools such as USB Protocol Analyzer
4. libusb running on Host PC to send packets