From 047f14d8778ac9f534517a15859976262b04aa43 Mon Sep 17 00:00:00 2001
From: Jesse Vincent <jesse@bestpractical.com>
Date: Mon, 16 Mar 2015 21:14:57 -0700
Subject: [PATCH] New high-performance SX1509 pin read/write support that
 doesn't send any i2c traffic until the calling code asks it to.

---
 sx1509_library.cpp | 28 ++++++++++++++++++++++++++++
 sx1509_library.h   |  9 ++++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/sx1509_library.cpp b/sx1509_library.cpp
index eddb20ea..32b4a78e 100644
--- a/sx1509_library.cpp
+++ b/sx1509_library.cpp
@@ -152,6 +152,34 @@ byte sx1509Class::rawReadPin(byte pin)
 		return (readWord(REG_DATA_B) & (1<<pin));
 }
 
+
+
+void sx1509Class::fetchPinStates() {
+    pinData = readWord(REG_DATA_B);  
+    
+}
+void sx1509Class::sendPinStates() {
+   writeWord(REG_DATA_B,pinData);  
+    
+}
+
+
+
+byte sx1509Class::readPrefetchedPin(byte pin) {
+   return (pinData & (1 << pin)); 
+}
+
+void sx1509Class::updatePinState(byte pin, byte highLow)
+{
+		if (highLow)	
+                    pinData =  pinData | (1 <<pin);
+		else
+		    pinData = pinData & ~(1<<pin);
+}
+
+
+
+
 byte sx1509Class::readPin(byte pin)
 {
 	
diff --git a/sx1509_library.h b/sx1509_library.h
index dac36dd8..0678986f 100644
--- a/sx1509_library.h
+++ b/sx1509_library.h
@@ -44,6 +44,9 @@ private:	// These private functions are not available to Arduino sketches.
 			// If you need to read or write directly to registers, consider
 			// putting the writeByte, readByte functions in the public section
 	uint8_t deviceAddress; // I2C Address of SX1509
+
+        unsigned int pinData; // used for the keyboardio hacks to do fewer i2c calls
+
 // Pin definitions:
 	byte pinInterrupt;
 	byte pinOscillator;
@@ -134,7 +137,11 @@ public:
 // -----------------------------------------------------------------------------
 	byte readPin(byte pin);
 	byte rawReadPin(byte pin);
-	
+	void fetchPinStates(void);
+        void sendPinStates(void);
+        byte readPrefetchedPin(byte pin);
+        void updatePinState(byte pin, byte highLow);
+
 // -----------------------------------------------------------------------------
 // ledDriverInit(byte pin, byte freq, bool log): This function initializes LED 
 //		driving on a pin. It must be called if you want to use the pwm or blink