Added i2c support via MCP23008

MCP23008.cpp

@@ -0,0 +1,143 @@
+// Code by Adafruit Industries/Limor Fried
+// License: LGPL
+
+#include <Wire.h>
+#include <avr/pgmspace.h>
+#include "MCP23008.h"
+#include <WProgram.h>
+
+
+////////////////////////////////////////////////////////////////////////////////
+// RTC_DS1307 implementation
+
+void MCP23008::begin(uint8_t addr) {
+  if (addr > 7) {
+    addr = 7;
+  }
+  i2caddr = addr;
+
+  Wire.begin();
+
+  // set defaults!
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_IODIR);
+  Wire.send(0xFF);  // all inputs
+  Wire.send(0x00);
+  Wire.send(0x00);
+  Wire.send(0x00);
+  Wire.send(0x00);
+  Wire.send(0x00);
+  Wire.send(0x00);
+  Wire.send(0x00);
+  Wire.send(0x00);
+  Wire.send(0x00);	
+  Wire.endTransmission();
+
+}
+
+void MCP23008::begin(void) {
+  begin(0);
+}
+
+void MCP23008::pinMode(uint8_t p, uint8_t d) {
+  uint8_t iodir;
+
+
+  // only 8 bits!
+  if (p > 7)
+    return;
+
+  // read the current IODIR
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_IODIR);	
+  Wire.endTransmission();
+
+  Wire.requestFrom(MCP23008_ADDRESS | i2caddr, 1);
+  iodir = Wire.receive();
+
+  // set the pin and direction
+  if (d == INPUT) {
+    iodir |= 1 << p; 
+  } else {
+    iodir &= ~(1 << p);
+  }
+
+  // write the new IODIR
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_IODIR);
+  Wire.send(iodir);	
+  Wire.endTransmission();
+}
+
+
+void MCP23008::digitalWrite(uint8_t p, uint8_t d) {
+  uint8_t gpio;
+
+  // only 8 bits!
+  if (p > 7)
+    return;
+
+  // read the current GPIO output latches
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_OLAT);	
+  Wire.endTransmission();
+
+  Wire.requestFrom(MCP23008_ADDRESS | i2caddr, 1);
+  gpio = Wire.receive();
+
+  // set the pin and direction
+  if (d == HIGH) {
+    gpio |= 1 << p; 
+  } else {
+    gpio &= ~(1 << p);
+  }
+
+  // write the new GPIO
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_GPIO);
+  Wire.send(gpio);	
+  Wire.endTransmission();
+}
+
+void MCP23008::pullUp(uint8_t p, uint8_t d) {
+  uint8_t gppu;
+
+  // only 8 bits!
+  if (p > 7)
+    return;
+
+  // read the current pullup resistor set
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_GPPU);	
+  Wire.endTransmission();
+
+  Wire.requestFrom(MCP23008_ADDRESS | i2caddr, 1);
+  gppu = Wire.receive();
+
+  // set the pin and direction
+  if (d == HIGH) {
+    gppu |= 1 << p; 
+  } else {
+    gppu &= ~(1 << p);
+  }
+
+  // write the new GPIO
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_GPPU);
+  Wire.send(gppu);	
+  Wire.endTransmission();
+}
+
+uint8_t MCP23008::digitalRead(uint8_t p) {
+  // only 8 bits!
+  if (p > 7)
+    return 0;
+
+  // read the current GPIO
+  Wire.beginTransmission(MCP23008_ADDRESS | i2caddr);
+  Wire.send(MCP23008_GPIO);	
+  Wire.endTransmission();
+
+  Wire.requestFrom(MCP23008_ADDRESS | i2caddr, 1);
+  return (Wire.receive() >> p) & 0x1;
+}

MCP23008.h

@@ -0,0 +1,34 @@
+// i2c expander library - slow I/O!
+
+// also works with the MCP23009
+
+// Don't forget the Wire library
+class MCP23008 {
+public:
+  void begin(uint8_t addr);
+  void begin(void);
+
+  void pinMode(uint8_t p, uint8_t d);
+  void digitalWrite(uint8_t p, uint8_t d);
+  void pullUp(uint8_t p, uint8_t d);
+  uint8_t digitalRead(uint8_t p);
+
+ private:
+  uint8_t i2caddr;
+};
+
+#define MCP23008_ADDRESS 0x20
+
+// registers
+#define MCP23008_IODIR 0x00
+#define MCP23008_IPOL 0x01
+#define MCP23008_GPINTEN 0x02
+#define MCP23008_DEFVAL 0x03
+#define MCP23008_INTCON 0x04
+#define MCP23008_IOCON 0x05
+#define MCP23008_GPPU 0x06
+#define MCP23008_INTF 0x07
+#define MCP23008_INTCAP 0x08
+#define MCP23008_GPIO 0x09
+#define MCP23008_OLAT 0x0A
+