Bus Pirate v3 is a universal bus interface that talks to electronics from a PC serial terminal. Get to know a chip without writing code. Eliminates a ton of early prototyping effort with new or unknown chips.

Protocols

1-Wire, I2C, SPI, JTAG, asynchronous serial (UART), MIDI, PC keyboard, HD44780 LCDs, and generic 2- and 3-wire libraries for custom protocols.

Features
USB interface, USB powered
5volt tolerant pins
0-6volt measurement probe
1Hz-40MHz frequency measurement
1kHz-4MHz pulse-width modulator, frequency generator
On-board multi-voltage pull-up resistors
On-board 3.3volt and 5volt power supplies with software reset
Macros for common operations
Bus traffic sniffers (SPI, I2C)
Transparent USB to serial bridge mode
10Hz-1MHz low-speed logic analyzer
Custom support in AVRDUDE , Flashrom , OpenOCD
AVR STK500 v2 programmer clone
Scriptable from Perl, Python, etc.
A bootloader for easy USB firmware updates
Uses DP6037 standard PCB layout
Open source (CC 0/Public Domain)

Support
Bus Pirate manual
Hardware overview
Chip demonstrations
Latest firmware
Bus Pirate forum on Dangerous Prototypes.