9
3.1.1.1.5 Reading
Note: after initialization is complete, reading the Configuration and Mode Registers is
recommended to ensure they have been set as desired. See the AD7799
manufacturer’s
datasheet for information regarding reads of the Configuration and Mode registers.
3.1.1.2 Temperature Channel
The temperature channel ADC is controlled and configured via a number of on-chip registers.
ALL communication to the temperature channel ADC starts with a write operation to the 8-bit
write-only Communication register.
Initializing the temperature channel ADC requires writing data to a sequence of four registers;
the Communication register, the Mode register, the Communication register, and the Filter
register.
3.1.1.2.1 Communication Register
Sending
0x20
to the communication register tells the ADC the following write will be to
the 8-bit Filter register.
3.1.1.2.2 Filter Register
Sending
0x03
to the Filter register sets the ADC’s update rate (f
ADC
) to 20 Hz.
3.1.1.2.3 Communication Register
Sending
0x10
to the Communication register tells the ADC the following write will be to
the 8-bit Mode register.
3.1.1.2.4 Mode Register
Sending
0x80
to the Mode register places the ADC into a single conversion mode.
From the AD7790 manufacturer’s datasheet:
“When single conversion mode is selected, the ADC powers up and performs a single
conversion, which occurs after a period 2/f
ADC
[100 ms]
. The conversion result in placed
in the data register, RDY goes low, and the ADC returns to power-down mode. The
conversion remains in the data register and RDY remains active (low) until the data is
read or another conversion is performed
.”
3.1.1.2.5 Reading
Note: after initialization is complete, reading the Filter and Mode registers is
recommended to ensure they have been set as desired. See the AD7790
manufacturer’s
datasheet for information regarding reads of the Filter and Mode registers.