AVR MCU bandgap reference


http://wp.me/ph3BR-1PZ

 

h_ttp://xiaolabadiy.tumblr.com/post/62501053512/bandgap-reference

 

 

抄來, 小改過

忘記出處

 


 

long detectVcc() {
// 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;

result = 1125300L / result; // Calculate Vcc (in mV); 1125300 = 1.1*1023*1000
return result; // Vcc in millivolts
}

void setup() { Serial.begin(9600);  Serial.println("bandgap measurement\n"); }

void loop() { Serial.print( detectVcc(), DEC ); Serial.println (" mV"); delay(1000); }

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