Power Pins

• 5V pins - These are the 5V power pins. They receive 5V output from USB and can supply ~100mA peak.
• 3V pin - This is the 3.3V power pin. It is the output from the 3.3V regulator and can supply ~100mA peak.
• GND pins - These are common ground for power and logic.

FTDI Data Pins

The following pins are found at the back of the board. The pin order matches the FTDI cables in the Adafruit shop and use 3.3V logic, but are 5V compliant. They should work in the vast majority of 3.3V and 5V signal systems.

• CTS -  Clear To Send control input. This pin is active low.
• TXD - UART data transmit pin. This pin sends the serial output.
• RXD - UART data receive pin. This pin receives the serial input.
• RTS - Ready To Send control output. This pin is active low.

Control Pins

• SU - SUSPEND pin. This pin is driven high when the device enters the USB suspend state.
• #SU - SUSPENDb pin. This pin is driven low when the device enters the USB suspend state.
• IO2 - GPIO pin. Can be used as a digital input or output.
• IO3 - GPIO pin. Can be used as a digital input or output.
• RST - Reset pin. This pin is active-low.

Modem Pins

• DSR - Data Set Ready control input. This pin is active low.
• DTR - Data Terminal Ready control output. This pin is active low.
• DCD - Data Carrier Detect control input. This pin is active low.
• RI - Ring Indicator control input. This pin is active low.

TX and RX LEDs

These LEDs are located towards the back of the board in front of the FTDI pins. They help with debugging data.

• R LED - The serial receive LED. It blinks when the chip receives data.
• T LED - The serial transmit LED. It blinks when the chip transmits data.