Instructions

229 C-Control Pro IDE

5.4 Analog-Digital-Converter

5.4.1 Mega

The Micro Controller has an Analog Digital Converter with a resolution of 10 Bit. I. e. measured

voltages can be displayed as integral numbers from 0 through 1023. Reference voltage for the lower

limit is GND level (0V). The reference voltage for the upper limit can be selected at will.

External Reference Voltage

AVCC with capacitor on AREF

Internal Reference Voltage 2.56V with capacitor on AREF

Analog Inputs ADC0 ... ADC7, ADC_BG, ADC_GND

For the ADC the Inputs ADC0 ... ADC7 (Port A.0 to A.7 with Mega32, Port F.0 to F.7 with

Mega128), an internal Band Gap (1.22V) or GND (0V) are available. ADC_BG and ADC_GND can

be used for review of the ADC.

If x is a digital measuring value then the corresponding voltage value u is calculated as follows:

u = x * Reference V oltage / 1024

If the external reference voltage e. g. produced by a reference voltage IC is 4.096V, then the differ-

ence of one bit of the digitized measuring value corresponds to a voltage difference of 4mV, or:

u = x * 0,004V

The result of an A/D conversion can be influenced, if any Port Bit (configured for output) on the same

Port as the A/D channel, is changed during the measurement.

Differential Inputs

ADC22x10 Differential Inputs ADC2, ADC2, Gain 10 ; Offset Measurement

ADC23x10 Differential Inputs ADC2, ADC3, Gain 10

ADC22x200 Differential Inputs ADC2, ADC2, Gain 200 ; Offset Measurement

ADC23x200 Differential Inputs ADC2, ADC3, Gain 200

ADC20x1 Differential Inputs ADC2, ADC0, Gain 1

ADC21x1 Differential Inputs ADC2, ADC1, Gain 1

ADC22x1 Differential Inputs ADC2, ADC2, Gain 1 ; Offset Measurement

ADC23x1 Differential Inputs ADC2, ADC3, Gain 1

ADC24x1 Differential Inputs ADC2, ADC4, Gain 1

ADC25x1 Differential Inputs ADC2, ADC5, Gain 1

ADC2 is the negative input.

The ADC can also perform differential measurements. The result can either be positive or negative.

The resolution during differential operation amounts to +/- 9 bit and is displayed in Two's Comple-

ment format. For differential operation an amplifier with gains of V: x1, x10, x200 is available. If x is a

digital measuring value then the corresponding voltage value u is calculated as follows: