Welcome Newbie. I am also a newbie, but just a step or two ahead of you.
- It is not clear which way round my 8*8 LED Matrix plugs in. One way round I get a single red flashing LED near the middle of the panel. Is this the right way round?
If you do not change the default program for the Rainbowduino, then installing the matrix and powering it up will result in one of two things:
a. nothing visible, and no damage either
b. one red flashing pixel, your only indication that it is installed correctly.
When you get b., you could note the side of the matrix that faces the red/blue connectors (markings on bottom of the Rainbowduino) and mark it.
- How do I get Ubuntu 11.10 to recognise the Driver USB. DMESG shows “unable to enumerate USB device on port 2”. I already have the Arduino IDE installed and my Arduino USB is recognised as ttyACM0.
I use Windows, so this may be different for you. I find that the three Arduinos I use show up on COM4, COM5, and COM6. Each device consistently stays on whichever I first saw it. In the Arduino 1.0 IDE, you need to select the type of board. Duemilanovae with 328 works for my Rainbowduino.
For downloads to work, both settings must be correct, or else I will get a nastygram from someone called avrdude when the program tries to download from IDE to Rainbowduino.
I have no idea if any of this applies to you, but perhaps it will spur your ideas.
- Will the Rainbowduino be able to power itself and the LED array from the USB.
It does for me, and it should for you, though going through the math makes me wonder a bit.
USB spec says that it must supply a minimum of 0.5 Amp at 5 volts. The max constant current for LEDs, according to the Rainbowduino spec, is 20.8mA, and LEDs can run on 10-25mA (or even less). The matrix has 64 of them, but each one is like 3 LEDs because they are separate for R, G, and B, so 192 total. 0.020 Amp * 192 = 3.84, except that Rainbowduino uses WMD (oops, I mean PWM) to apply current to the LEDs one eighth of the time (12.5% duty cycle) but at a high enough frequency that it fools the eye into thinking that it is always on. 3.84 * .125 = 0.48 Amp.
This leaves only 20mA for the Arduino itself to operate, and that’s the part I wonder about. I have yet to find actual current requirements for an Arduino or the Rainbowduino; it is not included in the Specifications in seeedstudio.com/wiki/Rainbowduino_v3.0. But I can tell you that I have the RainbowCube (and have had the matrix) running off of the Rainbowduino when the latter was plugged in to USB, and it has been working fine.
I have a blog you might be interested in checking out; google on Colan Arduino and you should find it.