Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI Data Sheet

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ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]

Atmel-8271H-AVR- ATmega-Datasheet_08/2014

temperature measurement can be calibrated in the application software. The software calibration requires that a 
calibration value is measured and stored in a register or EEPROM for each chip, as a part of the production test. 
The software calibration can be done utilizing the formula:

T = { [(ADCH << 8) | ADCL] - T

OS

} / k

where ADCn are the ADC data registers, k is a fixed coefficient and T

OS

 is the temperature sensor offset value 

determined and stored into EEPROM as a part of the production test.

These bits select the voltage reference for the ADC, as shown in 

. If these bits are changed during a 

conversion, the change will not go in effect until this conversion is complete (ADIF in ADCSRA is set). The 
internal voltage reference options may not be used if an external reference voltage is being applied to the AREF 
pin.

The ADLAR bit affects the presentation of the ADC conversion result in the ADC Data Register. Write one to 
ADLAR to left adjust the result. Otherwise, the result is right adjusted. Changing the ADLAR bit will affect the 
ADC Data Register immediately, regardless of any ongoing conversions. For a complete description of this bit, 
see 

This bit is an unused bit in the ATmega48A/PA/88A/PA/168A/PA/328/P, and will always read as zero.

The value of these bits selects which analog inputs are connected to the ADC. See 

 for details.

 

If 

these bits are changed during a conversion, the change will not go in effect until this conversion is complete 
(ADIF in ADCSRA is set).

Bit

7

6

5

4

3

2

1

0

Read/Write

R/W

R/W

R/W

R

R/W

R/W

R/W

R/W

Initial  Value

0

0

0

0

0

0

0

0

0

0

AREF, Internal V

ref

 turned off

0

1

AV

CC

 with external capacitor at AREF pin

1

0

Reserved

1

1

Internal 1.1V Voltage Reference with external capacitor at AREF pin