[vc_row][vc_column][vc_column_text]I/O Expander shield is a shield used to expand the number of I/Os of a pcDuino/Arduino Uno. It is based on the chipset MCP23017. The chipset MCP23017 communicates with Arduino Uno through I2C interface. It adds GPIOA and GPIOB, a total of 16 I/Os. There are two LEDs and two buttons on the shield. User can decide if they want to use the built-in LED/buttons or not by using the 4-bit DIP switch.

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• 16 bidirectional I/O ports. Default is input state.
• High-speed IIC interface (MCP23017): 100kHz, 400kHz, 1.7MHz
• Three hardware address pins allow up to eight devices on the bus
• Configurable interrupt output pin: can be configured for active-high (output), active-low (output) or open-drain (output)
• INTA and INTB can be configured to work independently or jointly
• Configurable interrupt sources: the interrupt changes according to the configured register defaults or pin level changes
• External reset input
• Low standby current: 1μA (max)
• Operating voltage:
  • 1.8V to 5.5V (-40 ° C to +85 ° C)
  • 2.7V to 5.5V (-40 ° C to +85 ° C)
  • 4.5V to 5.5V (-40 ° C to +125 ° C)

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1  x  pcDuino V2  

1  x  I/O Expander Shield  

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#include <core.h>
#include "Wire.h"

byte  mcp_address=0x20;      // I2C Address of MCP23017 Chip
byte  GPIOA=0x12;            // Register Address of Port A
byte  GPIOB=0x13;            // Register Address of Port B
byte  IODIRA=0x00;            // IODIRA register
byte  IODIRB=0x01;            // IODIRB register

void setup()
{
  //Send settings to MCP device
  Wire.begin();              // join i2c bus (address optional for master)
  Wire.beginTransmission(mcp_address);
  Wire.write(IODIRA); // IODIRA register
  Wire.write(0x03); // set GPIOA-0/GPIOA-1 to inputs
  Wire.endTransmission();
}

void loop()
{
  Wire.beginTransmission(mcp_address);
  Wire.write(GPIOA); // set MCP23017 memory pointer to GPIOB address
  Wire.endTransmission();
  Wire.requestFrom(0x20, 1); // request one byte of data from MCP20317
  int inputs=Wire.read(); // store the incoming byte into "inputs"

  if((inputs&0x01)==0)
  {
    Wire.beginTransmission(mcp_address);
    Wire.write(GPIOA);    // address bank A
    Wire.write(0x04);  // value to send GPIOA-2 HIGH
    Wire.endTransmission();
    printf("the s1 pressn-------------n");
  }
  else if((inputs&0x02)==0) 
  {
    Wire.beginTransmission(mcp_address);
    Wire.write(GPIOA);    // address bank A
    Wire.write(0x08);  // value to send GPIOA-3 HIGH
    Wire.endTransmission();
    printf("the s2 pressn-------------n");
  }
  else
  {
    Wire.beginTransmission(mcp_address);
    Wire.write(GPIOA);     // address bank A
    Wire.write((byte)0x00);  // value to send GPIOA LOW
    Wire.endTransmission();
  }
  delay(100);
}

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1. Install the I/O Expander Shield to the pcDuino board.

 2. Open the Arduino IDE

3. Slide the Jumper on the shield to the ON-side. Respectively slide the buttons S1 and S2 of the Jumper on the Shield to the ON–side

[/vc_column_text][/vc_tab][vc_tab title=”Schematic diagram” tab_id=”1399444039371-4-7″][vc_column_text]io expander shield SCH[/vc_column_text][/vc_tab][/vc_tour][/vc_column][/vc_row]