sorry about this. footnotes added below. Comparison Table
Glasgow HardSploit <https://hardsploit.io/>Tigard <https://www.crowdsupply.com/securinghw/tigard>JTAGulator <http://www.grandideastudio.com/jtagulator/>HydraBus <https://hydrabus.com/hydrabus-1-0-specifications>GoodFET <https://github.com/travisgoodspeed/goodfet>GreatFET <https://greatscottgadgets.com/greatfet/>BusBlaster <http://dangerousprototypes.com/docs/Bus_Blaster>BusPirate <http://dangerousprototypes.com/docs/Bus_Pirate> *UART* Y Y Y Y Y N Y N Y *SPI* Y Y Y N Y Y Y N Y *Parallel* Y Y N N N N Y N N *I2C* Y Y Y N Y Y Y N Y *JTAG/SWD* Y Y Y Y Y Y Y Y Y *Logic Analyzer* Y Y Through Bitmagic Y Y Y Y N Y *Extensibility* FPGA FPGA FTDI MCU MCU MCU MCU CPLD MCU *Interface* CLI,API CLI,GUI,API CLI,GUI,API CLI CLI CLI CLI CLI CLI *I/O count* ¹ 16 64 14 24 44 9 100 9 7 *Cascading* ³ Y N N N N N N N N *Indep. I/O* ⁴ 2 banks 8 banks 1 bank 1 bank 1 bank 1 bank 1 bank 1 bank 1 bank *I/O Voltages* 1.8-5 V 3.3 V, 5 V 1.8 V, 3.3 V, 5.5 V 1.4-3.3 V 3.3 V 3.3 V 3.3 V 1.5-3.3 V 3.3 V, 5 V *I/O Speed* ¹ ² 100 MHz 25 MHz 25 MHz 15 kHz 42 MHz 1 Mbps 50 MHz 6 MHz 1 Mbps *USB* Type C Type Mini-B Type C Type Mini-B Type Micro-B Type Mini-B Type Micro-B Type Mini-B Type Mini-B *Open Hardware* Y N Y Y Y Y Y Y Y *Cost* $130 $320 ⁵ $39 $170 $80 $50 $100 $45 $37
¹ In perfect conditions ² In Hz for target I/F bottleneck and bps for host I/F side bottleneck ³ Able to connect multiple devices together and synchronize them ⁴ I/O banks with independently controllable voltage ⁵ Unavailable at time of comparison