atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 240

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

18.8
240
Temperature Measurement
ATmega32/64/M1/C1
Example 2:
The temperature measurement is based on an on-chip temperature sensor that is coupled to a
single ended ADC input. MUX[4..0] bits in ADMUX register enables the temperature sensor. The
internal 2.56V voltage reference must also be selected for the ADC voltage reference source in
the temperature sensor measurement. When the temperature sensor is enabled, the ADC con-
verter can be used in single conversion mode to measure the voltage over the temperature
sensor.
As shown
when ADMUX value selects the temperature sensor as ADC input
Selection” on page 243.
two successive conversions are required. The correct temperature measurement will be the sec-
ond one.
One can also reduce this timing to one conversion by setting the ADMUX during the previous
conversion. Indeed the ADMUX can be programmed to select the temperature sensor just after
the beginning of the previous conversion start event and then the driver will be enabled 2 µS
before sampling and hold phase of temperature sensor measurement. See “Changing Channel
or Reference Selection” on page 232.
Figure 18-15. Temperature Sensor Block Diagram
–
–
–
–
–
ADCL will thus read 0x00, and ADCH will read 0x9C.
Writing zero to ADLAR right adjusts the result: ADCL = 0x70, ADCH = 0x02.
ADMUX = 0xFB (ADC3 - ADC2, 1x gain, 2.56V reference, left adjusted result)
Voltage on ADC3 is 300 mV, voltage on ADC2 is 500 mV.
ADCR = 512 * 1 * (300 - 500) / 2560 = -41 = 0x029.
ADCL will thus read 0x40, and ADCH will read 0x0A.
Writing zero to ADLAR right adjusts the result: ADCL = 0x00, ADCH = 0x29.
Figure
Temperature
Sensor
18-15, the temperature sensor is followed by a driver. This driver is enabled
The propagation delay of this driver is approximatively 2µS. Therefore
ADMUX = Temp. Sensor input
G=1
Enable when
ADC
Input
Multiplexer
ADMUX
to sampling
and hold
See “ADC Input Channel
7647A–AVR–02/08