For enhancement #5.

Add variable to prevent use of complex structure and free 7 byte of mem.

PCF8574.cpp

@@ -149,50 +149,90 @@ void PCF8574::readBuffer(bool force){
 	}
 }
 
-/**
+#ifndef PCF8574_LOW_MEMORY
- * Read value of all INPUT pin
+	/**
- * Debounce read more fast than 10millis, non managed for interrupt mode
+	 * Read value of all INPUT pin
- * @return
+	 * Debounce read more fast than 10millis, non managed for interrupt mode
- */
+	 * @return
-PCF8574::DigitalInput PCF8574::digitalReadAll(void){
+	 */
-	DEBUG_PRINTLN("Read from buffer");
+	PCF8574::DigitalInput PCF8574::digitalReadAll(void){
-	Wire.requestFrom(_address,(uint8_t)1);// Begin transmission to PCF8574 with the buttons
+		DEBUG_PRINTLN("Read from buffer");
-	lastReadMillis = millis();
+		Wire.requestFrom(_address,(uint8_t)1);// Begin transmission to PCF8574 with the buttons
-	if(Wire.available())   // If bytes are available to be recieved
+		lastReadMillis = millis();
-	{
+		if(Wire.available())   // If bytes are available to be recieved
-		  DEBUG_PRINTLN("Data ready");
+		{
-		  byte iInput = Wire.read();// Read a byte
+			  DEBUG_PRINTLN("Data ready");
+			  byte iInput = Wire.read();// Read a byte
 
-		  if ((iInput & readMode)>0){
+			  if ((iInput & readMode)>0){
-			  DEBUG_PRINT("Input ");
+				  DEBUG_PRINT("Input ");
-			  DEBUG_PRINTLN((byte)iInput, BIN);
+				  DEBUG_PRINTLN((byte)iInput, BIN);
 
-			  byteBuffered = byteBuffered | (byte)iInput;
+				  byteBuffered = byteBuffered | (byte)iInput;
-			  DEBUG_PRINT("byteBuffered ");
+				  DEBUG_PRINT("byteBuffered ");
-			  DEBUG_PRINTLN(byteBuffered, BIN);
+				  DEBUG_PRINTLN(byteBuffered, BIN);
-		  }
+			  }
-	}
+		}
 
-	DEBUG_PRINT("Buffer value ");
+		DEBUG_PRINT("Buffer value ");
-	DEBUG_PRINTLN(byteBuffered, BIN);
-
-	if ((bit(0) & readMode)>0) digitalInput.p0 = ((byteBuffered & bit(0))>0)?HIGH:LOW;
-	if ((bit(1) & readMode)>0) digitalInput.p1 = ((byteBuffered & bit(1))>0)?HIGH:LOW;
-	if ((bit(2) & readMode)>0) digitalInput.p2 = ((byteBuffered & bit(2))>0)?HIGH:LOW;
-	if ((bit(3) & readMode)>0) digitalInput.p3 = ((byteBuffered & bit(3))>0)?HIGH:LOW;
-	if ((bit(4) & readMode)>0) digitalInput.p4 = ((byteBuffered & bit(4))>0)?HIGH:LOW;
-	if ((bit(5) & readMode)>0) digitalInput.p5 = ((byteBuffered & bit(5))>0)?HIGH:LOW;
-	if ((bit(6) & readMode)>0) digitalInput.p6 = ((byteBuffered & bit(6))>0)?HIGH:LOW;
-	if ((bit(7) & readMode)>0) digitalInput.p7 = ((byteBuffered & bit(7))>0)?HIGH:LOW;
-
-	if ((readMode & byteBuffered)>0){
-		byteBuffered = ~readMode & byteBuffered;
-		DEBUG_PRINT("Buffer hight value readed set readed ");
 		DEBUG_PRINTLN(byteBuffered, BIN);
-	}
+
-	DEBUG_PRINT("Return value ");
+		if ((bit(0) & readMode)>0) digitalInput.p0 = ((byteBuffered & bit(0))>0)?HIGH:LOW;
-	return digitalInput;
+		if ((bit(1) & readMode)>0) digitalInput.p1 = ((byteBuffered & bit(1))>0)?HIGH:LOW;
-};
+		if ((bit(2) & readMode)>0) digitalInput.p2 = ((byteBuffered & bit(2))>0)?HIGH:LOW;
+		if ((bit(3) & readMode)>0) digitalInput.p3 = ((byteBuffered & bit(3))>0)?HIGH:LOW;
+		if ((bit(4) & readMode)>0) digitalInput.p4 = ((byteBuffered & bit(4))>0)?HIGH:LOW;
+		if ((bit(5) & readMode)>0) digitalInput.p5 = ((byteBuffered & bit(5))>0)?HIGH:LOW;
+		if ((bit(6) & readMode)>0) digitalInput.p6 = ((byteBuffered & bit(6))>0)?HIGH:LOW;
+		if ((bit(7) & readMode)>0) digitalInput.p7 = ((byteBuffered & bit(7))>0)?HIGH:LOW;
+
+		if ((readMode & byteBuffered)>0){
+			byteBuffered = ~readMode & byteBuffered;
+			DEBUG_PRINT("Buffer hight value readed set readed ");
+			DEBUG_PRINTLN(byteBuffered, BIN);
+		}
+		DEBUG_PRINT("Return value ");
+		return digitalInput;
+	};
+#else
+	/**
+	 * Read value of all INPUT pin in byte format for low memory usage
+	 * Debounce read more fast than 10millis, non managed for interrupt mode
+	 * @return
+	 */
+	byte PCF8574::digitalReadAll(void){
+		DEBUG_PRINTLN("Read from buffer");
+		Wire.requestFrom(_address,(uint8_t)1);// Begin transmission to PCF8574 with the buttons
+		lastReadMillis = millis();
+		if(Wire.available())   // If bytes are available to be recieved
+		{
+			  DEBUG_PRINTLN("Data ready");
+			  byte iInput = Wire.read();// Read a byte
+
+			  if ((iInput & readMode)>0){
+				  DEBUG_PRINT("Input ");
+				  DEBUG_PRINTLN((byte)iInput, BIN);
+
+				  byteBuffered = byteBuffered | (byte)iInput;
+				  DEBUG_PRINT("byteBuffered ");
+				  DEBUG_PRINTLN(byteBuffered, BIN);
+			  }
+		}
+
+		DEBUG_PRINT("Buffer value ");
+		DEBUG_PRINTLN(byteBuffered, BIN);
+
+		byte byteRead = byteBuffered;
+
+		if ((readMode & byteBuffered)>0){
+			byteBuffered = ~readMode & byteBuffered;
+			DEBUG_PRINT("Buffer hight value readed set readed ");
+			DEBUG_PRINTLN(byteBuffered, BIN);
+		}
+		DEBUG_PRINT("Return value ");
+		return byteRead;
+	};
+#endif
 
 /**
  * Read value of specified pin

PCF8574.h

@@ -18,6 +18,9 @@
 // Uncomment to enable printing out nice debug messages.
 // #define PCF8574_DEBUG
 
+// Uncomment for low memory usage this prevent use of complex DigitalInput structure and free 7byte of memory
+// #define PCF8574_LOW_MEMORY
+
 // Define where debug output will be printed.
 #define DEBUG_PRINTER Serial
 
@@ -55,16 +58,6 @@
 
 class PCF8574 {
 public:
-	struct DigitalInput {
-		uint8_t p0;
-		uint8_t p1;
-		uint8_t p2;
-		uint8_t p3;
-		uint8_t p4;
-		uint8_t p5;
-		uint8_t p6;
-		uint8_t p7;
-	} digitalInput;
 
 	PCF8574(uint8_t address);
 	PCF8574(uint8_t address, uint8_t sda, uint8_t scl);
@@ -77,7 +70,23 @@ public:
 
 	void readBuffer(bool force = true);
 	uint8_t digitalRead(uint8_t pin);
-	DigitalInput digitalReadAll(void);
+	#ifndef PCF8574_LOW_MEMORY
+		struct DigitalInput {
+			uint8_t p0;
+			uint8_t p1;
+			uint8_t p2;
+			uint8_t p3;
+			uint8_t p4;
+			uint8_t p5;
+			uint8_t p6;
+			uint8_t p7;
+		} digitalInput;
+
+
+		DigitalInput digitalReadAll(void);
+	#else
+		byte digitalReadAll(void);
+	#endif
 	void digitalWrite(uint8_t pin, uint8_t value);
 
 private:

examples/readAll_Interrupt_lowMemory/readAll_Interrupt_lowMemory.ino

@@ -0,0 +1,46 @@
+#include "Arduino.h"
+#include "PCF8574.h"
+
+// To use in low memory mode and prevent use of 7byte you must decomment the line
+// #define PCF8574_LOW_MEMORY
+// in the library
+
+// For arduino uno only pin 1 and 2 are interrupted
+#define ARDUINO_UNO_INTERRUPTED_PIN 2
+
+// Function interrupt
+void keyChangedOnPCF8574();
+
+// Set i2c address
+PCF8574 pcf8574(0x39, ARDUINO_UNO_INTERRUPTED_PIN, keyChangedOnPCF8574);
+unsigned long timeElapsed;
+void setup()
+{
+	Serial.begin(115200);
+
+	pcf8574.pinMode(P0, INPUT);
+	pcf8574.pinMode(P1, INPUT);
+	pcf8574.pinMode(P2, INPUT);
+	pcf8574.begin();
+
+	Serial.println("START");
+
+	timeElapsed = millis();
+}
+
+bool keyChanged = false;
+void loop()
+{
+	if (keyChanged){
+		byte di = pcf8574.digitalReadAll();
+		Serial.print("READ VALUE FROM PCF: ");
+		Serial.println(di, BIN);
+//		delay(5);
+		keyChanged= false;
+	}
+}
+
+void keyChangedOnPCF8574(){
+	// Interrupt called (No Serial no read no wire in this function, and DEBUG disabled on PCF library)
+	 keyChanged = true;
+}