From 05717a198cecd8dbc239d31a8537d990f41abe66 Mon Sep 17 00:00:00 2001
From: "David A. Mellis" <d.mellis@arduino.cc>
Date: Fri, 14 Dec 2007 04:21:59 +0000
Subject: [PATCH] Adding analogReference() function - needs testing on an
 ATmega8 (but works on the ATmega 168).

---
 build/macosx/Arduino.xcodeproj/project.pbxproj |  3 +--
 build/shared/lib/keywords.txt                  |  4 ++++
 hardware/cores/arduino/wiring.c                |  4 ----
 hardware/cores/arduino/wiring.h                |  5 +++++
 hardware/cores/arduino/wiring_analog.c         | 16 ++++++++++++++--
 5 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/build/macosx/Arduino.xcodeproj/project.pbxproj b/build/macosx/Arduino.xcodeproj/project.pbxproj
index 93167b34e..32724f892 100644
--- a/build/macosx/Arduino.xcodeproj/project.pbxproj
+++ b/build/macosx/Arduino.xcodeproj/project.pbxproj
@@ -116,7 +116,7 @@
 			productName = App;
 			productReference = 33DD8FB6096AC8DA0013AF8F /* Arduino.app */;
 			productSettingsXML = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>
-<!DOCTYPE plist PUBLIC \"-//Apple//DTD PLIST 1.0//EN\" \"http://www.apple.com/DTDs/PropertyList-1.0.dtd\">
+<!DOCTYPE plist PUBLIC \"-//Apple Computer//DTD PLIST 1.0//EN\" \"http://www.apple.com/DTDs/PropertyList-1.0.dtd\">
 <plist version=\"1.0\">
 <dict>
 	<key>CFBundleDevelopmentRegion</key>
@@ -903,7 +903,6 @@
 		33FFFD3F0965B1E40016AC38 /* Project object */ = {
 			isa = PBXProject;
 			buildConfigurationList = 33FFFD400965B1E40016AC38 /* Build configuration list for PBXProject "Arduino" */;
-			compatibilityVersion = "Xcode 2.4";
 			hasScannedForEncodings = 0;
 			mainGroup = 33FFFD3D0965B1E40016AC38;
 			productRefGroup = 33FFFD3D0965B1E40016AC38;
diff --git a/build/shared/lib/keywords.txt b/build/shared/lib/keywords.txt
index 160d236f4..098b79d15 100644
--- a/build/shared/lib/keywords.txt
+++ b/build/shared/lib/keywords.txt
@@ -79,6 +79,7 @@ constrain	KEYWORD2	constrain_
 cos	KEYWORD2	cos_
 {}		curlybraces
 --		decrement
+DEFAULT	KEYWORD1	DEFAULT
 default	KEYWORD1	default
 delay	KEYWORD2	delay_
 delayMicroseconds	KEYWORD2
@@ -88,6 +89,7 @@ delayMicroseconds	KEYWORD2
 else	KEYWORD1	else
 ==		equality
 exp	KEYWORD2	exp_
+EXTERNAL	KEYWORD1	EXTERNAL
 false	KEYWORD1	false
 float	KEYWORD1	float
 float	KEYWORD2	float_
@@ -101,6 +103,7 @@ if	KEYWORD1	if_
 !=		inequality
 int	KEYWORD1	int
 int	KEYWORD2	int_
+INTERNAL	KEYWORD1	INTERNAL
 <<		leftshift
 <		lessthan
 <=		lessthanorequalto
@@ -148,6 +151,7 @@ flush	KEYWORD2
 digitalWrite	KEYWORD2
 digitalRead	KEYWORD2
 pinMode	KEYWORD2
+analogReference	KEYWORD2
 analogRead	KEYWORD2
 analogWrite	KEYWORD2
 attachInterrupt	KEYWORD2
diff --git a/hardware/cores/arduino/wiring.c b/hardware/cores/arduino/wiring.c
index 5dda822d3..ae8fcdd16 100755
--- a/hardware/cores/arduino/wiring.c
+++ b/hardware/cores/arduino/wiring.c
@@ -170,10 +170,6 @@ void init()
 	sbi(TCCR2, WGM20);
 #endif
 
-	// set a2d reference to AVCC (5 volts)
-	cbi(ADMUX, REFS1);
-	sbi(ADMUX, REFS0);
-
 	// set a2d prescale factor to 128
 	// 16 MHz / 128 = 125 KHz, inside the desired 50-200 KHz range.
 	// XXX: this will not work properly for other clock speeds, and
diff --git a/hardware/cores/arduino/wiring.h b/hardware/cores/arduino/wiring.h
index e0c53156f..df43e6c67 100755
--- a/hardware/cores/arduino/wiring.h
+++ b/hardware/cores/arduino/wiring.h
@@ -57,6 +57,10 @@ extern "C"{
 #define FALLING 2
 #define RISING 3
 
+#define INTERNAL 3
+#define DEFAULT 1
+#define EXTERNAL 0
+
 // undefine stdlib's abs if encountered
 #ifdef abs
 #undef abs
@@ -93,6 +97,7 @@ void pinMode(uint8_t, uint8_t);
 void digitalWrite(uint8_t, uint8_t);
 int digitalRead(uint8_t);
 int analogRead(uint8_t);
+void analogReference(uint8_t mode);
 void analogWrite(uint8_t, int);
 
 void beginSerial(long);
diff --git a/hardware/cores/arduino/wiring_analog.c b/hardware/cores/arduino/wiring_analog.c
index 0ab32ebb6..30c5642cc 100755
--- a/hardware/cores/arduino/wiring_analog.c
+++ b/hardware/cores/arduino/wiring_analog.c
@@ -25,12 +25,24 @@
 #include "wiring_private.h"
 #include "pins_arduino.h"
 
+uint8_t analog_reference = DEFAULT;
+
+void analogReference(uint8_t mode)
+{
+	// can't actually set the register here because the default setting
+	// will connect AVCC and the AREF pin, which would cause a short if
+	// there's something connected to AREF.
+	analog_reference = mode;
+}
+
 int analogRead(uint8_t pin)
 {
 	uint8_t low, high, ch = analogInPinToBit(pin);
 
-	// the low 4 bits of ADMUX select the ADC channel
-	ADMUX = (ADMUX & (unsigned int) 0xf0) | (ch & (unsigned int) 0x0f);
+	// set the analog reference (high two bits of ADMUX) and select the
+	// channel (low 4 bits).  this also sets ADLAR (left-adjust result)
+	// to 0 (the default).
+	ADMUX = (analog_reference << 6) | (pin & 0x0f);
 
 	// without a delay, we seem to read from the wrong channel
 	//delay(1);