Datasheet

ATmega164A/PA/324A/PA/644A/PA/1284/P
 2018 Microchip Technology Inc. Data Sheet Complete DS40002070A-page 256
Example:
ADMUX = 0xED (ADC3 - ADC2, 10× gain, 2.56V reference, left adjusted result)
Voltage on ADC3 is 300mV, voltage on ADC2 is 500mV.
ADCR = 512 × 10 × (300 - 500) / 2560 = -400 = 0x270
ADCL will thus read 0x00, and ADCH will read 0x9C. Writing zero to ADLAR right adjusts the result:
ADCL = 0x70, ADCH = 0x02.
Table 23-2. Correlation between input voltage and output codes
V
ADCn
Read code Corresponding decimal value
V
ADCm
+ V
REF
/GAIN 0x1FF 511
V
ADCm
+ 0.999V
REF
/GAIN 0x1FF 511
V
ADCm
+ 0.998V
REF
/GAIN 0x1FE 510
... ... ...
V
ADCm
+ 0.001V
REF
/GAIN 0x001 1
V
ADCm
0x000 0
V
ADCm
- 0.001V
REF
/GAIN 0x3FF -1
... ... ...
V
ADCm
- 0.999V
REF
/GAIN 0x201 -511
V
ADCm
- V
REF
/GAIN 0x200 -512