Hello. I am trying to use a 4-pin FTDI cable from adafruit to connect my FIO to my computer. the four pins are GND, VCC, Tx and Rx. When I connect them and hook the cable to the PC, the LED at the bottom of the board flashes, but nothing else. The computer does not recognize a device plugged in, and the ON LED on the FIO board does not light up. Does anyone have experience with this cable? DO I need to tie DTR hi/lo in order for this setup to work? Thanks.
Perhaps you should give us a link to exactly what "FTDI" cable you are using.
That the power lights "flash" on connection and then go out indicates that you have short-circuited the Vcc and ground somehow or rather, severely overloaded them. Disconnect the cable from the FIO and just plug it into the computer and see whether it is recognised.
I note that the FIO operates at 3.3V. If you attempt to supply 5V to its Vcc, its internal regulator will probably pull that down to 3.3V and the USB supply will shut down to protect everything. You should only connect the 5V from a FTDI cable to "Vin" on the FIO. If however you have a FTDI cable which is designed to supply 3.3V, it will simply not be able to supply enough current at this voltage, to power the FIO and the FTDI chip will shut down.