Buspirate v4
-Protocols1-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 powered5volt tolerant pins0-6volt measurement probe1Hz-40MHz frequency measurement1kHz-4MHz pulse-width modulator, frequency generatorOn-board multi-voltage pull-up resistorsOn-board 3.3volt and 5volt power supplies with software resetMacros for common operationsBus traffic sniffers (SPI, I2C)Transparent USB->serial bridge mode10Hz-1MHz low-speed logic analyzer
-Custom support in AVRDUDE , Flashrom , OpenOCDAVR STK500 v2 programmer cloneScriptable from Perl, Python, etc.A bootloader for easy USB firmware updatesOpen source (CC 0/public domain)New in Bus Pirate v4256K program space, 4 times more flash than v3Integrated, on-board USB (faster)Data storage EEPROM to store settingsSoftware pull-up voltage selection: 3.3volt, 5volt, or external supply2 extra I/O pinsMultipurpose button