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Improve reading ADC result #345

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Merged
merged 1 commit into from
Nov 2, 2020
Merged

Improve reading ADC result #345

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18 changes: 5 additions & 13 deletions cores/arduino/wiring_analog.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,6 @@ void analogReference(uint8_t mode)

int analogRead(uint8_t pin)
{
uint8_t low, high;

#if defined(analogPinToChannel)
#if defined(__AVR_ATmega32U4__)
Expand Down Expand Up @@ -74,27 +73,20 @@ int analogRead(uint8_t pin)
// without a delay, we seem to read from the wrong channel
//delay(1);

#if defined(ADCSRA) && defined(ADCL)
#if defined(ADCSRA) && defined(ADC)
// start the conversion
sbi(ADCSRA, ADSC);

// ADSC is cleared when the conversion finishes
while (bit_is_set(ADCSRA, ADSC));

// we have to read ADCL first; doing so locks both ADCL
// and ADCH until ADCH is read. reading ADCL second would
// cause the results of each conversion to be discarded,
// as ADCL and ADCH would be locked when it completed.
low = ADCL;
high = ADCH;
// ADC macro takes care of reading ADC register.
// avr-gcc implements the proper reading order: ADCL is read first.
return ADC;
#else
// we dont have an ADC, return 0
low = 0;
high = 0;
return 0;
#endif

// combine the two bytes
return (high << 8) | low;
}

// Right now, PWM output only works on the pins with
Expand Down