In the MQX documentation for the TWR-K20D50M board it states "For using USB Host mode, jumpers on position: TWR-K20D50M board, J26 on position 1-2 (That's correct), TWR-K20D50M board, J30 on position 5-6 (VREGIN)." This last jumper J30 5-6 IS INCORRECT. That position, when the TWR board is hooked up to a USB Device (like a mouse) leaves the MCU UNPOWERED. J30 5-6 powers the MCU from the micro USB port. A USB Device has no power! When connected to a PC having J30 on position 1-2 powers the MCU with 1.8 volts.When connected to a PC having J30 on position 5-6 powers the PC with anywhere from 5.2 to 6.5 volts (PC USB Powered).