/*
* There are two on board MCP23017(U2 and U4) IO Expander ICs on this Shield
* Select jumper positions of AD1=AD2=AD3=0, to set the Address of U2 as 0x20
* Select jumper positions of AD4=0; AD5=0; AD6=1, to set the Address of U4 as 0x21
* Digital Pins 0 - 7 belongs to PORTA and 8 - 15 belongs to PORTB of U2
* Digital Pins 24 - 27 belongs to PORTA and 16 - 23 belongs to PORTB of U4
*/
#include "Wire.h"
byte U2PortA, U2PortB, U4PortA, U4PortB =0; // Define variables to hold I/O port readings.
void setup()
{
Serial.begin(9600); // Begin Serial Communication
Wire.begin(); // Begin I2C Communication
/*
* The following code starts I2C communication with MCP23017(U2).Please refer MCP23017 datasheet
* for register addresses. Sets all GPIOs of this IC to INPUT
*/
Wire.beginTransmission(0x20); // Starts communication with MCP23017(U2) IC
Wire.write(0x00); // Set MCP23017 memory pointer to IODIRA address
Wire.write(0xFF); // Set all pins of PORTA to outputs
Wire.endTransmission(); // Ends I2C communication with MCP23017(U2) IC
Wire.beginTransmission(0x20); // Starts communication with MCP23017(U2) IC
Wire.write(0x01); // Set MCP23017 memory pointer to IODIRB address
Wire.write(0xFF); // Set all pins of PORTB to outputs
Wire.endTransmission(); // Ends I2C communication with MCP23017(U2) IC
/*
* The following code starts I2C communication with MCP23017(U4).Please refer MCP23017 datasheet
* for register addresses. Sets all GPIOs of this IC to INPUT
*/
Wire.beginTransmission(0x21); // Starts communication with MCP23017(U4) IC
Wire.write(0x00); // Set MCP23017 memory pointer to IODIRA address
Wire.write(0xFF); // Set all PORTA pins to OUTPUT
Wire.endTransmission(); // Ends I2C communication with MCP23017(U4) IC
Wire.beginTransmission(0x21); // Starts communication with MCP23017(U4) IC
Wire.write(0x01); // Set MCP23017 memory pointer to IODIRB address
Wire.write(0xFF); // Set all PORTB pins to OUTPUT
Wire.endTransmission(); // Ends I2C communication with MCP23017(U4) IC
}
void loop()
{
Wire.beginTransmission(0x20); // Starts I2C Communication with MCP23017(U2) IC
Wire.write(0x12); // Set MCP23017 memory pointer to PORTA address
Wire.endTransmission(); // Ends I2C communication with U2
Wire.requestFrom(0x20, 1); // Request one byte of data from MCP20317(U2)
U2PortA=Wire.read(); // Store the incoming byte of PORTA into "U2PortA"
Wire.beginTransmission(0x20); // Start I2C communication with U2
Wire.write(0x13); // Set MCP23017 memory pointer to PORTB address
Wire.endTransmission(); // Ends I2C communication with U2
Wire.requestFrom(0x20, 1); // Request one byte of data from MCP20317(U2)
U2PortB=Wire.read(); // Store the incoming byte of PORTB into "U2PortB"
Wire.beginTransmission(0x21); // Start I2C communication with MCP23017(U4)
Wire.write(0x12); // Set MCP23017 memory pointer to PORTA address
Wire.endTransmission(); // Ends I2C communication with U4
Wire.requestFrom(0x21, 1); // Request one byte of data from MCP20317(U4)
U4PortA=Wire.read(); // Store the incoming byte of PORTA into "U4PortA"
Wire.beginTransmission(0x21); // Start I2C communication with U4
Wire.write(0x13); // Set MCP23017 memory pointer to PORTB address
Wire.endTransmission(); // Ends I2C communication with U4
Wire.requestFrom(0x21, 1); // Request one byte of data from MCP20317
U4PortB=Wire.read(); // Store the incoming byte of PORTB into "U4PortB"
Serial.print("U2 PORTA: " );
Serial.println(U2PortA, BIN); // Print the contents of the PORTA register in binary
Serial.print("U2 PORTB: " );
Serial.println(U2PortB, BIN); // Print the contents of the PORTB register in binary
delay(500);
Serial.print("U4 PORTA: " );
Serial.println(U4PortA, BIN); // Print the contents of the PORTA register in binary
Serial.print("U4 PORTB: " );
Serial.println(U4PortB, BIN); // Print the contents of the PORTB register in binary
delay(500);
}
