My first google searches ended in disappointment – using the built in Terminal program with Screen was unsuccessful (probably because it doesn’t seem like you can set the baudrate). Update: it turns out that you can set the baudrate with screen using an argument like so – “screen /dev/ttyWHATEVER 115200″. Thanks goes to the David in the comments below. After a little searching, it looked like the few serial terminal applications for Mac were old and outdated, but I did manage to find ZTerm. It’s simple and basic – perfect for use with the bus pirate.

Don’t forget that you need to have already installed the FTDI driver so that your computer will see the device over USB. Start Zterm and choose the correct port in the popup window (if it isn’t already chosen automatically). Then you need to change the connection settings to talk to the Bus Pirate properly. Go to Settings->Connection and set it like this:

Data Rate: 115200
Data Bits: 8
Parity: None
Stop bits: 1

The rest you can leave at the default. [UPDATE] On newer firmware versions you’ll need to deselect Xon/Xoff as per Ian in the comments below.

Hit ok and go back to the terminal window to start talking

Hit enter to start communicating. Entering ? will bring up the list of commands like so:

To test some functionality of the bus pirate, we’re going to measure the voltage on the ADC pin. We’ll do this by putting the Bus Pirate into just about any mode besides HiZ – we’ll choose 1-Wire since it’s simple to set up.

Enter “m” to bring up the mode menu, choose 1-Wire by entering “2″. Hook up some voltage to the ADC pin (see the bottom of the Bus Pirate for it’s pinout). Then enter “d” to read the value on the pin. I connected the pin to the 5V input from the USB line, so it reads 5.1V. You can see that full process in the terminal below.

That’s it for the basics! See the Bus Pirate site for more examples of how to use this nice piece of hardware.

There are two USB ports for anything that takes USB power (5V) – of course, these ports are for power only (no data). You can use these to control the Woot-Off lights without cutting and soldering the cord, and something else (USB Fan? Light? Humping Dog?). There are also four pads toward the middle so you can solder in anything else that takes 5V power.

USB Power Shield board

Schematic here.

Since the Arduino can only supply maybe 300mA while on USB power and 600mA from its small 5V regulator (using DC in), I’ve included the stuff necessary to add a 7805 regulator and related components to allow up to 1A (if you use a heatsink). You can always leave these pads empty if you don’t plan on using that much power. The Woot-Off Lights will need at least the 5V regulator on the Arduino. There are also LEDs to show if the regulator and board itself are powered – these can be omitted as well.

The board uses four 2N3906 to control power of up to 200mA at 5V to four devices. By writing the corresponding pin LOW on the Arduino, you turn on the transistor and allow current to flow from 5V to the device (and then, hopefully, out to GND). Very Simple.