I2C 16-bit Interface

Description of the Design

This card allows up to 16 additional I/O pins to be added to a Microprocessor, such as an Arduino,

The card has an I2C interface (MCP23017) which is a two-wire interface consisting of a clock from the Microprocessor and a bi-directional data line.

The card has three address bits allowing up to 8 cards to be used for a total of 128 I/O bits.

Connectors

• J1-J3 = A0-A2 I2C address select (binary address value)

• J4 = I2C connector
• Pin 1 (G) = GND
• Pin 2 (V) = Vcc (+5V)
• Pin 3 (D) = SDA (Data)
• Pin 4 (C) = SCLK (Clock) 
• J13-J6 = GPA0-GPA7 - Parallel I/O Connections. Uses GVS convention for 3-pin connectors.
• J22-J16 = GPB0-GPB7 - Parallel I/O Connections. Uses GVS convention for 3-pin connectors.
• Pin 1 (G) = Ground
• Pin 2 (V) = Vcc (+5V)
• Pin 3 (S) = Signal
• J5 (IA) =  Interrupt A output
• J14 (IB) =  Interrupt B output
  

10K Pull up resistors

• R1-R2 are pullups on the I2C lines.
• There should only be 1 set of terminators on the I2C lines.
• Do not install of there are terminators in other locations (consider source as well) on I2C lines.
  

Mounting Holes

Four 4-40 mounting holes allow the board to be firmly mounted horizontally or vertically.

The board dimensions are 1.3" x 2.0". The mounting holes are 1.0" x 1.7".

Links

• Adafruit Arduino MCP23017 Library

V3 Improvement Log

• Add a second I2C connector as pass-through for multiple I2C cards.