ATmega16 ADC learning

[imranahmed]

Please let me know how to understand following lines:

ADMUX=(1<<REFS0); // AVcc with external capacitor at AREF
ADCSRA=(1<<ADEN)|(1<<ADPS2)|(1<<ADPS1)|(1<<ADPS0);

unsigned int ADC_read(unsigned char ch)
{
ch= ch & 0b00000111; // channel must be b/w 0 to 7
ADMUX |= ch; // selecting channel

ADCSRA|=(1<<ADSC); // start conversion
while(!(ADCSRA & (1<<ADIF))); // waiting for ADIF, conversion complete
ADCSRA|=(1<<ADIF); // clearing of ADIF, it is done by writing 1 to it

return (ADC);
}

 

[FvM]

What's your particular question about the code?

Do you understand the WinAVR way of representing register bits, e.g. 1<<REFS0 ?
REFS0 is a bit number (between 0 and 7), 1<<REFS0 is a bit mask.

REFS0 is defined as 6, according to the bit position in ADMUX register, review the ATmega datasheet in case of doubt.

1 << 6 equals 0x40, the bitmask to access the REFS0 bit.

 

[imranahmed]

Understanding of masking and i am not use WinAVR.

 

[FvM]

Understanding of masking and i am not use WinAVR.

In fact it's just plain C. But you need to know how the register bits are defined in the processor specific header files.