+ version 0.1.04 (0.1.03 = intermediate)

+ removed beginTransmission from read8() -> speed++
+ removed endTransmission from read8() -> speed
+ changed address to uint8_t

libraries/PCF8574/PCF8574.cpp

@@ -2,103 +2,118 @@
 //    FILE: PCF8574.cpp
 //  AUTHOR: Rob Tillaart
 //    DATE: 02-febr-2013
-// VERSION: 0.1.02
+// VERSION: 0.1.04
 // PURPOSE: I2C PCF8574 library for Arduino
-//     URL: 
+//     URL:
 //
 // HISTORY:
+// 0.1.04 2015-05-09 removed ambiguity in read8()
+// 0.1.03 2015-03-02 address int -> uint8_t
 // 0.1.02 replaced ints with uint8_t to reduce footprint;
 //        added default value for shiftLeft() and shiftRight()
 //        renamed status() to lastError();
-// 0.1.01 added value(); returns last read 8 bit value (cached); 
+// 0.1.01 added value(); returns last read 8 bit value (cached);
 //        value() does not always reflect the latest state of the pins!
 // 0.1.00 initial version
-// 
+//
 
 #include "PCF8574.h"
 
 #include <Wire.h>
 
-PCF8574::PCF8574(int address) 
+PCF8574::PCF8574(uint8_t deviceAddress)
 {
-  _address = address;
+    _address = deviceAddress;
-  Wire.begin();
+    Wire.begin();
+    // TWBR = 12; // 400KHz
 }
 
+// removed Wire.beginTransmission(addr);
+// with  @100KHz -> 265 micros()
+// without @100KHz -> 132 micros()
+// without @400KHz -> 52 micros()
+// TODO @800KHz -> ??
 uint8_t PCF8574::read8()
 {
-  Wire.beginTransmission(_address);
+    if (Wire.requestFrom(_address, (uint8_t)1) != 1)
-  Wire.requestFrom(_address, 1);
+    {
+        _error = 10;
+        return _data; // last value
+    }
 #if (ARDUINO <  100)
-   _data = Wire.receive();
+    _data = Wire.receive();
 #else
-   _data = Wire.read();
+    _data = Wire.read();
 #endif
-  _error = Wire.endTransmission();
+    return _data;
-  return _data;
 }
 
 uint8_t PCF8574::value()
 {
-  return _data;
+    return _data;
 }
 
 void PCF8574::write8(uint8_t value)
 {
-  Wire.beginTransmission(_address);
+    _data = value;
-  _data = value;
+    Wire.beginTransmission(_address);
-  Wire.write(_data);
+    Wire.write(_data);
-  _error = Wire.endTransmission();
+    _error = Wire.endTransmission();
 }
 
+// pin should be 0..7
 uint8_t PCF8574::read(uint8_t pin)
 {
-  PCF8574::read8();
+    PCF8574::read8();
-  return (_data & (1<<pin)) > 0;
+    return (_data & (1<<pin)) > 0;
 }
 
+// pin should be 0..7
 void PCF8574::write(uint8_t pin, uint8_t value)
 {
-  PCF8574::read8();
+    PCF8574::read8();
-  if (value == LOW) 
+    if (value == LOW)
-  {
+    {
-    _data &= ~(1<<pin);
+        _data &= ~(1<<pin);
-  }
+    }
-  else 
+    else
-  {
+    {
-    _data |= (1<<pin);
+        _data |= (1<<pin);
-  }
+    }
-  PCF8574::write8(_data); 
+    PCF8574::write8(_data);
 }
 
+// pin should be 0..7
 void PCF8574::toggle(uint8_t pin)
 {
-  PCF8574::read8();
+    PCF8574::read8();
-  _data ^=  (1 << pin);
+    _data ^=  (1 << pin);
-  PCF8574::write8(_data); 
+    PCF8574::write8(_data);
 }
 
+// n should be 0..7
 void PCF8574::shiftRight(uint8_t n)
 {
-  if (n == 0 || n > 7 ) return;
+    if (n == 0 || n > 7 ) return;
-  PCF8574::read8();
+    PCF8574::read8();
-  _data >>= n;
+    _data >>= n;
-  PCF8574::write8(_data); 
+    PCF8574::write8(_data);
 }
 
+// n should be 0..7
 void PCF8574::shiftLeft(uint8_t n)
 {
-  if (n == 0 || n > 7) return;
+    if (n == 0 || n > 7) return;
-  PCF8574::read8();
+    PCF8574::read8();
-  _data <<= n;
+    _data <<= n;
-  PCF8574::write8(_data); 
+    PCF8574::write8(_data);
 }
 
 int PCF8574::lastError()
 {
-  int e = _error;
+    int e = _error;
-  _error = 0;
+    _error = 0;
-  return e;
+    return e;
 }
 //
 // END OF FILE

libraries/PCF8574/PCF8574.h

@@ -2,13 +2,13 @@
 //    FILE: PCF8574.H
 //  AUTHOR: Rob Tillaart
 //    DATE: 02-febr-2013
-// VERSION: 0.1.02
+// VERSION: 0.1.04
 // PURPOSE: I2C PCF8574 library for Arduino
-//     URL: 
+//     URL:
 //
 // HISTORY:
 // see PCF8574.cpp file
-// 
+//
 
 #ifndef _PCF8574_H
 #define _PCF8574_H
@@ -19,30 +19,30 @@
 #include "WProgram.h"
 #endif
 
-#define PCF8574_LIB_VERSION "0.1.02"
+#define PCF8574_LIB_VERSION "0.1.04"
 
 class PCF8574
 {
-  public:
+public:
-  PCF8574(int address); 
+    PCF8574(uint8_t deviceAddress);
-	 
-  uint8_t read8(); 
-  uint8_t read(uint8_t pin); 
-  uint8_t value();  
 
-  void write8(uint8_t value); 
+    uint8_t read8();
-  void write(uint8_t pin, uint8_t value); 
+    uint8_t read(uint8_t pin);
+    uint8_t value();
 
-  void toggle(uint8_t pin);
+    void write8(uint8_t value);
-  void shiftRight(uint8_t n=1);
+    void write(uint8_t pin, uint8_t value);
-  void shiftLeft(uint8_t n=1);
+
-  
+    void toggle(uint8_t pin);
-  int lastError();
+    void shiftRight(uint8_t n=1);
-  
+    void shiftLeft(uint8_t n=1);
-  private:
+
-  int _address;
+    int lastError();
-  uint8_t _data;
+
-  int _error;
+private:
+    uint8_t _address;
+    uint8_t _data;
+    int _error;
 };
 
 #endif