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Analog-Digital Example

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Code

Here we read out an analog voltage and get a 10 bit result according to AREF. In other words the result in volts will be . This function will do one conversion, then shut down the AD-module completely, saving precious power. This code is written for Atmega48/88/168 but can easily be ported to other AVR-devices.

//Read a single-ADC-value according to AREF
uint16_t ReadADC(){
        //Temporary variable
	uint16_t result = 0;
	PRR ^= (1<<PRADC);//Set the Power Reduction ADC-bit to 0
	//Set the adc-channel in use, and the reference voltage
	ADMUX = (0<<MUX3)|(1<<MUX2)|(0<<MUX1)|(0<<MUX0);//ADC4 and AREF voltage-reference
	DIDR0 = (1<<ADC4D);//Disable the digital buffer at this pin
 
	ADCSRA = (1<<ADEN)|(1<<ADSC);//Start conversion
	while(ADCSRA & (1<<ADSC))//Wait until the conversion is finished
		;
        //Get the result, first get the 8 lower bits
	result = (uint16_t)ADCL;
        //Then the 2 higher bits(since this is a 10 bit conversion, only the two lowest bits will ever be set)
	result += (((uint16_t)ADCH)<<8);
 
	ADCSRA = 0x00;//Turn off the ADC-module
	PRR |= (1<<PRADC);
 
	return result;//Return
}

--Oybo 06:06, 31 October 2007 (CET)