[EDIT: There is an updated version with tenting over the smaller vias and updated silkscreen, see BusPirate-v3b-FTDI-0.2]
For a long time, I’ve been interested in the Bus Pirate, made by Dangerous Prototypes. It looks like it would be extremely handy for figuring out the best way to interface with a component, e.g., an EEPROM, a temperature sensor or a real-time clock, without having to program and reprogram a microcontroller until you get it right. Once you have figured out with the Bus Pirate how you want to use the component, then you can code it up.
I’ve been interested in trying to make one myself, however, it is a complex circuit layout, and I didn’t relish the idea of either trying to make it work on a single-sided PCB, or trying to make a double-sided PCB. Fortunately, this fellow Laen runs a PCB prototyping batch order that seems reasonably priced. In order to save some dough, though, I thought I might be able to get away with removing the FTDI FT232RL chip and support components, and use my FTDI USB-to-TTL cable (based on the same chip) instead.
This is the result:
It turns out that after removing the FT232RL, the board can be squeezed down into a somewhat smaller footprint, which should make for an even cheaper board to produce. I have lingering doubts, particularly about the ground planes’ ability to carry the heat away from the voltage regulators (which are now more tightly spaced), and also about the silk-screen layer fitting in among pads and vias. I plan to order the boards soon, and try it out.
The original Bus Pirate was released to the public domain without restriction. I have released it with my updates under the Creative Commons Attribution Share Alike v3.0 license.
Note that I haven’t built this yet, expect an update later after I’ve gotten it assembled, programmed, and tested.