I am having trouble connecting to my JTAG-based device with the USB Debug Adapter, but I can connect with the Serial Debug Adapter (EC2). What could be the problem?
The USB Debug adapter measures the voltage on the JTAG TDI pin to determine appropriate logic levels.
Placing a pull-down resistor on TDI will make your hardware incompatible with the USB Debug Adapter. Since the USB Debug Adapter measures the voltage on TDI to determine the logic levels for your device, TDI must be pulled to the supply voltage.
For C2 devices, the C2CK pin must be pulled to the supply voltage.