Datasheet

FTDI Breakout

At the bottom is 6 pins in a row that we call the FTDI header. You can use these pins to program the Pro Trinket with

an FTDI cable or FTDI Friend. You can also use it for serial debugging.

GND - (Black BLK wire on FTDI Cable) same as the power ground pins

GND - ditto

5V - same as the VBUS pin

RX - same as the RX pin

TX - same as the TX pin

RST - (Green GRN wire on FTDI Cable) there's a 0.1uF capacitors in between this pin and the Reset pin, so that

Arduino-compatible programmers will work correctly with the DTR/RTS-toggle technique