+ version 0.1.04 (0.1.03 = intermediate)

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

Author: RobTillaart

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;
- Wire.begin();
+ _address = deviceAddress;
+ 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);
- Wire.requestFrom(_address, 1);
+ if (Wire.requestFrom(_address, (uint8_t)1) != 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;
- Wire.write(_data);
- _error = Wire.endTransmission();
+  _data = value;
+  Wire.beginTransmission(_address);
+  Wire.write(_data);
+  _error = Wire.endTransmission();
 }
 
+// pin should be 0..7
 uint8_t PCF8574::read(uint8_t pin)
 {
- PCF8574::read8();
- return (_data & (1<<pin)) > 0;
+  PCF8574::read8();
+  return (_data & (1<<pin)) > 0;
 }
 
+// pin should be 0..7
 void PCF8574::write(uint8_t pin, uint8_t value)
 {
- PCF8574::read8();
- if (value == LOW) 
- {
- _data &= ~(1<<pin);
- }
- else 
- {
- _data |= (1<<pin);
- }
- PCF8574::write8(_data); 
+  PCF8574::read8();
+  if (value == LOW)
+  {
+  _data &= ~(1<<pin);
+  }
+  else
+  {
+  _data |= (1<<pin);
+  }
+  PCF8574::write8(_data);
 }
 
+// pin should be 0..7
 void PCF8574::toggle(uint8_t pin)
 {
- PCF8574::read8();
- _data ^= (1 << pin);
- PCF8574::write8(_data); 
+  PCF8574::read8();
+  _data ^= (1 << pin);
+  PCF8574::write8(_data);
 }
 
+// n should be 0..7
 void PCF8574::shiftRight(uint8_t n)
 {
- if (n == 0 || n > 7 ) return;
- PCF8574::read8();
- _data >>= n;
- PCF8574::write8(_data); 
+  if (n == 0 || n > 7 ) return;
+  PCF8574::read8();
+  _data >>= n;
+  PCF8574::write8(_data);
 }
 
+// n should be 0..7
 void PCF8574::shiftLeft(uint8_t n)
 {
- if (n == 0 || n > 7) return;
- PCF8574::read8();
- _data <<= n;
- PCF8574::write8(_data); 
+  if (n == 0 || n > 7) return;
+  PCF8574::read8();
+  _data <<= n;
+  PCF8574::write8(_data);
 }
 
 int PCF8574::lastError()
 {
- int e = _error;
- _error = 0;
- return e;
+  int e = _error;
+  _error = 0;
+  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:
- PCF8574(int address); 
- 
- uint8_t read8(); 
- uint8_t read(uint8_t pin); 
- uint8_t value(); 
-
- void write8(uint8_t value); 
- void write(uint8_t pin, uint8_t value); 
-
- void toggle(uint8_t pin);
- void shiftRight(uint8_t n=1);
- void shiftLeft(uint8_t n=1);
- 
- int lastError();
- 
- private:
- int _address;
- uint8_t _data;
- int _error;
+public:
+  PCF8574(uint8_t deviceAddress);
+
+  uint8_t read8();
+  uint8_t read(uint8_t pin);
+  uint8_t value();
+
+  void write8(uint8_t value);
+  void write(uint8_t pin, uint8_t value);
+
+  void toggle(uint8_t pin);
+  void shiftRight(uint8_t n=1);
+  void shiftLeft(uint8_t n=1);
+
+  int lastError();
+
+private:
+  uint8_t _address;
+  uint8_t _data;
+  int _error;
 };
 
 #endif