From 76c964d32b13f1fc01e3a5b07460d96f2dcaecd6 Mon Sep 17 00:00:00 2001
From: "David A. Mellis" <d.mellis@arduino.cc>
Date: Mon, 2 Jan 2012 14:20:28 -0500
Subject: [PATCH] Adding INPUT_PULLUP option pinMode(). (Paul Stoffregen).

This also changes pinMode(pin, INPUT); to explicitly disable the pull-up resistor, even if it was previously set.

http://code.google.com/p/arduino/issues/detail?id=246
---
 build/shared/lib/keywords.txt                   |  1 +
 hardware/arduino/cores/arduino/Arduino.h        |  1 +
 hardware/arduino/cores/arduino/wiring_digital.c | 10 +++++++++-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/build/shared/lib/keywords.txt b/build/shared/lib/keywords.txt
index 730de4e75..74fb064e5 100644
--- a/build/shared/lib/keywords.txt
+++ b/build/shared/lib/keywords.txt
@@ -3,6 +3,7 @@
 HIGH	LITERAL1	Constants
 LOW	LITERAL1	Constants
 INPUT	LITERAL1	Constants
+INPUT_PULLUP	LITERAL1	Constants
 OUTPUT	LITERAL1	Constants
 DEC	LITERAL1	Serial_Print
 BIN	LITERAL1	Serial_Print
diff --git a/hardware/arduino/cores/arduino/Arduino.h b/hardware/arduino/cores/arduino/Arduino.h
index bfec9437e..830c9952f 100755
--- a/hardware/arduino/cores/arduino/Arduino.h
+++ b/hardware/arduino/cores/arduino/Arduino.h
@@ -20,6 +20,7 @@ extern "C"{
 
 #define INPUT 0x0
 #define OUTPUT 0x1
+#define INPUT_PULLUP 0x2
 
 #define true 0x1
 #define false 0x0
diff --git a/hardware/arduino/cores/arduino/wiring_digital.c b/hardware/arduino/cores/arduino/wiring_digital.c
index 97ef1343d..584a28a23 100755
--- a/hardware/arduino/cores/arduino/wiring_digital.c
+++ b/hardware/arduino/cores/arduino/wiring_digital.c
@@ -32,17 +32,25 @@ void pinMode(uint8_t pin, uint8_t mode)
 {
 	uint8_t bit = digitalPinToBitMask(pin);
 	uint8_t port = digitalPinToPort(pin);
-	volatile uint8_t *reg;
+	volatile uint8_t *reg, *out;
 
 	if (port == NOT_A_PIN) return;
 
 	// JWS: can I let the optimizer do this?
 	reg = portModeRegister(port);
+	out = portOutputRegister(port);
 
 	if (mode == INPUT) { 
 		uint8_t oldSREG = SREG;
                 cli();
 		*reg &= ~bit;
+		*out &= ~bit;
+		SREG = oldSREG;
+	} else if (mode == INPUT_PULLUP) {
+		uint8_t oldSREG = SREG;
+                cli();
+		*reg &= ~bit;
+		*out |= bit;
 		SREG = oldSREG;
 	} else {
 		uint8_t oldSREG = SREG;