Digilent 410-221P - Manual

P P m m o o d d T T M M P P 2 2 ™ ™ R R e e f f e e r r e e n n c c e e M M a a n n u u a a l l
Revision: October 11, 2011
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Overview
The PmodTMP2 is a temperature sensor and
thermostat control board built around the
Analog Devices ADT7420.
Features include:
•
Up to 16-bit resolution
•
Typical accuracy better than 0.25 °C
•
I 2 C interface with 4 selectable
addresses
•
240ms continuous conversion time
•
Support for 3.3v and 5v interfaces
•
No calibration required
•
Programmable
overtemperature/undertemperature
control pins.
Functional Description
The PmodTMP2 uses an 8-pin connector that
allows for communication via I
2
C, and provides
pins to daisy-chain the PmodTMP2 to other I 2 C
devices. The PmodTMP2 also provides two 2-
pin headers for selecting the I
2 C address of the
chip, and two 2-pin headers for controlling
external devices based upon temperature
thresholds defined by the user in software.
I
2
C Interface
The PmodTMP2’s onboard ADT7420 chip acts
as a slave device using the industry standard
I
2 C communication scheme. To communicate
with the PmodTMP2 device the I 2 C master
device must specify a slave address (0x48-
0x4B) and a flag indicating whether the
communication is a read (1) or a write (0). This
is followed by the actual data transfer. For the
ADT7420, the data transfer should consist of
the address of the desired device register
followed by the data to be written to the
specified register. To read from a register the
master must write the desired register address
to ADT7420, then send an I
2 C restart
condition, and send a new read request to the
ADT7420. If the master does not generate a
restart condition prior to attempting the read,
then the value written to the address register
will be reset to 0x00.
As some registers stored 16-bit values as 8-bit
register pairs, the ADT7420 will automatically
increment the address register of the device
when accessing certain registers such as the
temperature registers and the threshold
registers. This allows for the master to use a
single read or write request to access both the
low and high bytes of these registers. A
complete listing of registers and their behavior
can be found in the ADT7420 datasheet
available on the Analog Devices web site.
The I
2 C interface standard uses two signal
lines. These are I 2 C data and I 2 C clock. These
signals map to the serial data (SDA) and serial
clock (SCL) respectively on the ADT7420.
Connector J1 – I2C Communications
Pin
Signal Description
1, 2 SCL I2C Clock
3, 4 SDA I2C Data
5, 6 GND Power Supply Ground
7, 8 VCC Power Supply (3.3V/5V)
Interface Connector Signal Description