add src

src/CPUVolt.cpp

@@ -0,0 +1,41 @@
+/*\ =========================================================================
+|*|
+|*| CPUVolt.cpp
+|*|
+|*| Function to use the internal registers in the ATMega cpu to calculate
+|*| the processors AVcc:
+|*|
+|*| =========================================================================
+\*/
+
+#include <avr/io.h>
+#include <Arduino.h>
+
+#include "CPUVolt.h"
+
+signed long readVcc() {
+    // Read 1.1V reference against AVcc
+    // Set the reference to Vcc and the measurement to the internal 1.1V reference
+
+#if defined(__AVR_ATmega32U4__) || defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
+    ADMUX = _BV(REFS0) | _BV(MUX4) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
+#elif defined (__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__)
+    ADMUX = _BV(MUX5) | _BV(MUX0);
+#elif defined (__AVR_ATtiny25__) || defined(__AVR_ATtiny45__) || defined(__AVR_ATtiny85__)
+    ADMUX = _BV(MUX3) | _BV(MUX2);
+#else
+    ADMUX = _BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1);
+#endif
+
+    delay(2);                         // Wait for Vref to settle
+    ADCSRA |= _BV(ADSC);              // Start conversion
+    while (bit_is_set(ADCSRA, ADSC)); // measuring
+
+    uint8_t low  = ADCL;              // must read ADCL first - it then locks ADCH
+    uint8_t high = ADCH;              // unlocks both
+
+    long result = (high << 8) | low;  // convert to 32 bit signed value
+
+    result = 1125300L / result;       // Calculate Vcc (in mV); 1125300 = 1.1 * 1023 * 1000
+    return result;                    // Vcc in millivolts
+}

src/CPUVolt.h

@@ -0,0 +1,14 @@
+/*\ =========================================================================
+|*|
+|*| Library to use the internal registers in the ATMega cpu to calculate
+|*| the processor's Vcc voltage:
+|*|
+|*| =========================================================================
+\*/
+
+#ifndef CPUVOLT_H_INC
+#define CPUVOLT_H_INC
+
+signed long readVcc();
+
+#endif