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Adding analogReference() function - needs testing on an ATmega8 (but works on the ATmega 168).

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This commit is contained in:
David A. Mellis
2007-12-14 04:21:59 +00:00
parent 444c2dee32
commit 05717a198c
5 changed files with 24 additions and 8 deletions
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4
hardware/cores/arduino/wiring.c
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@ -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

5
hardware/cores/arduino/wiring.h
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@ -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);

16
hardware/cores/arduino/wiring_analog.c
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@ -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);