Datasheet

Figure 22-14. Differential Measurement Range
0
Output Code
0x1FF
0x000
V
REF
/GAIN
Differential Input
Volta ge (Volts )
0x3FF
0x200
- V
REF
/GAIN
The table below shows the resulting output codes if the differential input channel pair (ADCn - ADCm) is
selected with a gain of GAIN and a reference voltage of VREF.
Table 22-2. Correlation between Input Voltage and Output Codes
V
ADCn
Read code Corresponding Decimal Value
V
ADCm
+ V
REF
/GAIN 0x1FF 511
V
ADCm
+ 0.999 V
REF
/GAIN 0x1FF 511
V
ADCm
+ 0.998 V
REF
/GAIN 0x1FE 510
... ... ...
V
ADCm
+ 0.001 V
REF
/GAIN 0x001 1
V
ADCm
0x000 0
V
ADCm
- 0.001 V
REF
/GAIN 0x3FF -1
... ... ...
V
ADCm
- 0.999 V
REF
/GAIN 0x201 -511
V
ADCm
- V
REF
/GAIN 0x200 -512
Example:
ADMUX = 0xED (ADC3 - ADC2, 10× gain, 2.56V reference, left adjusted result)
Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
ADCR = 512 × 10 × (300 - 500) / 2560 = -400 = 0x270
ADCL will thus read 0x00, and ADCH will read 0x9C.
Atmel ATmega16M1/32M1/64M1 [DATASHEET]
Atmel-8209F-ATmega16M1/32M1/64M1_Datasheet_Complete-10/2016
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