Fitlet3: COM + GPIO connector pinout

General COM + GPIO connector pinout

Note! GPIO is not supported by Microsoft Windows

Pin Number	RS232+GPIO	RS485 Half duplex +GPIO	RS485 Full Duplex +GPIO
1	Power In	Power In	Power In
2	GPO (output)	GPO (output)	GPO (output)
3	GPO (output)	GPO (output)	GPO (output)
4	GPI (Input)	GPI (Input)	GPI (Input)
5	GPI (Input)	GPI (Input)	GPI (Input)
6	TXD	Data-	TX-
7	RXD		RX+
8	CTS		RX-
9	RTS	Data+	TX+
10	GND	GND	GND

The COM port connector contains: Serial communication (RS232, RS485 Half duplex, and RS485 Full duplex). GPIO (2 Input and 2 Output).

Serial communication pinout:

Pin Number	RS232	RS485 Half duplex	RS485 Full Duplex
6	TX	TXN/RXN	TXN
7	RX	-	RXP
8	CTS#	-	RXN
9	RTS#	TXP/RXP	TXP

GPIO pinout:

Pin Number	GPIO
1	VCC
2	GPO 0
3	GPO 1
4	GPI 0
5	GPI 1
10	GND

• The GPIO requires an external VCC to function. (up to 24V)
• The GPIO feature needs the newest FPGA version.

GPIO access explanations:

1. fitlet3 has 2 GPI and 2 GPO.

   GPI: Pins 4 and 5
   GPO: Pins 2 and 3

   Actual connector's pinout:

2. The GPIOs are controlled by the PCA9555 SMBUS I/O expander: https://www.ti.com/lit/gpn/pca9555

   It is located on the SMBUS address 0x20 in 7-bit format or 0x40 in 8-bit format.
   The GPIO map:

3. The GPIOs are controlled through SMBUS I/O expander registers: Input Port 1 (Command Byte: 0x01) and Output Port 1 (Command Byte: 0x03)

   To control GPO0 - write 0 or 1 to SMBUS address 0x20, byte 0x03, bit 0x05
   To control GPO1 - write 0 or 1 to SMBUS address 0x20, byte 0x03, bit 0x06
   To read GPI0 - read from SMBUS address 0x20, byte 0x01, bit 0x07
   To read GPI1 - read from SMBUS address 0x20, byte 0x01, bit 0x01