NEX ROBOTICS Fire Bird V ATMEGA2560 Software Manual page 97

7.2.2 ADCSRB – ADC Control and Status Register B
Bit 7
-
Read / Write R
Initial Value 0
Bit 3 – MUX5: Analog Channel and Gain Selection Bit
This bit is used together with MUX4:0 in ADMUX to select which combination in of analog
inputs are connected to the ADC. If this bit is changed during a conversion, the change will not
go in effect until this conversion is complete. For more details refer to table 26.4 in the
ATMEGA2560 datasheet.
7.2.3 ADMUX– ADC Multiplexer Selection Register
Bit 7
REFS1
Read / Write R/W
Initial Value 0
Bit 7:6 – REFS1:0: Reference Selection Bits
As shown in Table 7.2, these bits select the voltage reference for the ADC. 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.
REFS1 REFS0
0
0
1
1
Note:
If 10x or 200x gain is selected, only 2.56 V should be used as Internal Voltage Reference. For
differential conversion, only 1.1V cannot be used as internal voltage reference.
© NEX Robotics Pvt. Ltd. and ERTS Lab IIT Bombay, INDIA
ADPS2 ADPS1
0 0
0 0
0 1
0 1
1 0
1 0
1 1
1 1
Table 7.1 ADC prescaler selections
6 5
ACME -
R/W R
0 0
6 5
REFS0 ADLAR
R/W R/W
0 0
0 AREF, Internal VREF turned off
1 AVCC with external capacitor at AREF pin
0 Internal 1.1V Voltage Reference with external capacitor at AREF pin
1 Internal 2.56V Voltage Reference with external capacitor at AREF pin
Table 7.2: Voltage reference selection for ADC
Fire Bird V ATMEGA2560 Software Manual
ADPS0 Division Factor
0 2
1 2
0 4
1 8
0 16
1 32
0 64
1 128
4 3
- MUX5 ADTS2
R R/W R/W
0 0
4 3
MUX4 MUX3 MUX2
R/W R/W R/W
0 0
Voltage Reference Selection
2 1 0
ADTS1 ADTS0
R/W R/W
0 0 0
2 1 0
MUX1 MUX0
R/W R/W
0 0 0
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