Rainbow-electronics ATmega3290P_V Manuel d'utilisateur télécharger pdf (Page 214)

100

101

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ATmega329/3290/649/6490

2552H–AVR–11/06

Figure 97. Differential Measurement Range

ADMUX = 0xFB (ADC3 - ADC2, 1.1V reference, left adjusted result)

Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.

ADCR = 512 * (300 - 500) / 1100 = -93 = 0x3A3.

ADCL will thus read 0xC0, and ADCH will read 0xD8. Writing zero to ADLAR right

adjusts the result: ADCL = 0xA3, ADCH = 0x03.

Table 94. Correlation Between Input Voltage and Output Codes

ADCn

Read Code Corresponding Decimal Value

ADCm

+ V

REF

0x1FF 511

ADCm

511

512

REF

0x1FF 511

ADCm

510

512

REF

0x1FE 510

... ... ...

ADCm

512

REF

0x001 1

ADCm

0x000 0

ADCm

512

REF

0x3FF -1

... ... ...

ADCm

511

512

REF

0x201 -511

ADCm

- V

REF

0x200 -512

Output Code

0x1FF

0x000

REF

Differential Input

Voltage (Volts)

0x3FF

0x200

- V

REF

1 2 ... 209 210 211 212 213 214 215 216 217 218 219 ... 374 375

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