Introducing the Bumble-b and using it to control a LED matrix

The Bumble-b

Hi all,

The past week I have been playing around with my new Bumble-b, as I mentioned in my last post. Basically what I did with it is control an LED matrix. After doing that I made it in to a USB Device! Thanks to the simple library LUFA. Now I can use a simple echo > /dev/ttyACM0 command to send a text message to the display. Meaning that I have now /dev/matrix!

In this post I hope to explain how to use the Bumble-b, a  programmable USB chip, including its own built in programmer, for just $20. I would also like to encourage people here in Israel to start playing with this, since its cheap and easy to order way to get started with amateur electronics.

Here is a quick introduction video (followed by a detail post):

What is the Bumble-b?

The bumble-b is a USB programmable AVR chip with a programmer built in to it (called a breakout board). It is an AVR chip, meaning that its based on something that is widely used (the model is at90usb162). Moreover, since it has a USB connector right on it , this makes the creation of USB devices really simple. But not only USB devices alone.

For those who are thinking about getting an arduino, the main advantage I can see to an arduino over the Bumble-b is that it has analog-to-digital converters, which means its more built for connecting sensors, for things like robots. If that is not what you’re looking for, the Bumble-b will serve you well as a starting project, and is cheaper.

For more information, check out dflecher’s website (also for ordering), the bumble-b datasheet and the #bumbleb IRC channel.

Compiling code with gcc-avr (yes! now with 100% gcc)

Although I am linking here to a scripts I wrote, which should help you avoid writing in the shell, I do want to stress, that unlike the PIC project, here the compiler that is used is gcc-avr, which is fully  open  source.  I will get in to the specifics of how to use it in the IDE section.

How to get it in to programming mode

If you get a Bumble-b and plug it in right away, it will identify itself as a serial device on your computer. This is NOT the programmer, this is an initial program dflecher ships the Bumble-b with. The program lets you control the pins by sending them serial calls. Although it really is a useful program, you will want to install your own. To do that you need to set the Bumble-b to DFU mode (Device Firmware Update). This is mentioned in the schematic, but I will go over it here again:

1. Connect pin 21 (HWB) to pin 12 (GND)
2. connect a button between pin 9 (RESET) and pin 12 (GND)

Bumble-b in programmer mode

Now to go in to DFU mode press the REST button you installed. You should see in dmesg output:
usb 3-2: new full speed USB device using uhci_hcd and address 13
usb 3-2: New USB device found, idVendor=03eb, idProduct=2ffa
usb 3-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-2: Product: AT90USB162 DFU
usb 3-2: Manufacturer: ATMEL
usb 3-2: SerialNumber: 1.0.5

After getting in to programming mode, you can upload compiled .hex files to it. The programmer that is used is called dfu-programmer. It exists in the Debian repository (Kaplan, no excuses now). The commands to flash a .hex file will be:
dfu-programmer at90usb162 erase
dfu-programmer at90usb162 flash program.hex

But you can just use the scripts I wrote to do this. As explained in the next section.

Setting up an IDE environment in linux

The frustrating part for me was that unlike piklab that I used for the PICs, I could not find an IDE that will support the Bumble-b’s dfu-programmer out of the box. But rest assured! I found how to set one up. Thanks to Ori Iran’s guidelines I manage to set up an lightweight IDE called Geany to work with the bumble-b. Here are the steps:

1. Download my script packages. And extract them where you want to develop.
2. Get Geany with your distro’s repository, and open it.
3. Create a new .c file and save it (you can also open “hello_world.c” in the script package).
4. Open the ‘Build’ menu and select “Set includes and arguments”, You should get the window in the photo.
5. Set the fields as shown in the photo below (“./compile %f”  in compile field, “./program %f” in the build field, and “./run” in the execute field”).



6. You are good to go. Now to program just press ‘compile’, then “build” and ‘execute’ (don’t forget to press the RESET button before pressing ‘build’!).

The Geany IDE

LUFA library – How easy it is to make USB devices

After getting my LED matrix to display messages, I wanted to make use of the USB port, and get the matrix to work as a USB device, this was much simpler than I expected. Once I had the code to control the matrix, it was simply a matter of copying it and using LUFA.

LUFA (Lightweight USB Framework for AVRs) is a library that will let you get the Bumble-b to work as a USB device. It can be used as  a mouse, a keyboard, a joystick, a storage device and anything really (there is a full list is on the site).

To get the LED matrix to work off USB, all I had to do is copy the Demo that located in Demos/Device/ClassDriver/CDC. I also used code modified by dflecher (he built a USB missile launcher with it). Note that you will change the following lines in the makefiles of the LUFA Demo in order to use it with the bumble-b:

1. BOARD=BUMBLEB
2. MCU=at90usb162
3. F_CPU = 16000000

There is more info about what pins do (like joysticks buttons) in the LUFA readme on the bumble-b.

You can also download my matrix code and have a look.

More info?

• I will mention again that there is an IRC chat room for the #bumbleb on freenode. There is also a chat room on AVRs in general.

• dflecher’s site has all the information about the bumble-b. Also a great thanks to him for putting up with my questions 🙂 .
• AVR freaks is also a good place to look for things.
• You can also take a look at the youtube videos I have been posting the last few days

Code published in the post

Just to make sure you saw all the code published in the post

• Geany-Bumble-b scripts
• matrix.c code without the USB control
• Matrix control with the LUFA library (type ‘make’ in the CDC_matrix dir to compile).

That’s it. What are you waiting for? Amateur electronics is at your grasp!