The PmodTMP2 is an ambient temperature sensor powered by the Analog Devices ADT7420. Through the I²C interface, users may appreciate a resolution of 0.0078°C through 16 bits of data.
 

Interfacing with the Pmod

The PmodTMP2 communicates with the host board via the I²C protocol. Users may select one of the four I²C addresses based on the status of the JP1 and JP2 jumper blocks. A table listing the various settings and resulting address is provided below.
 

I²C Address Selection

 

I2C Addresses
JP2	JP1	Device Address
Open	Open	0x4B (0b10001011)
Open	Shorted	0x4A (0b1001010)
Shorted	Open	0x49 (0b1001001)
Shorted	Shorted	0x48 (0b1001000)

To read the temperature data from the PmodTMP2, users must first call the Analog Devices chip by whichever slave address you have set with the jumper blocks and then write the register address of the most significant byte of the temperature data (0x00).

Then, issue a restart condition and perform a read for two bytes of data (the register address is auto-incremented). Users may also notice that because the register address for the temperature data is 0x00, they may read the two data registers upon power-up without having to write to the address register because it is already in the correct location. The address register will need to be written to for subsequent readings.

The PmodTMP2 can also be set up to trigger two external output pins, CT (critical temperature) and INT (overtemperature or undertemperature interrupt). The CT pin is triggered whenever the critical temperature is reached which starts out at a default temperature of 147 °C. The INT pin by default triggers whenever the high temperature defined by the THIGH or the low temperature defined by TLOW is detected. Users may also enable a comparator mode so that status of each of the pins will not change until the hysteresis value has been passed.
 

Pinout Description Table

 

Header J1
Pin	Signal	Description
1 & 5	SCL	Serial Clock
2 & 6	SDA	Serial Data
3 & 7	GND	Power Supply Ground
4 & 8	VCC	Positive Power Supply

 

Jumper Blocks
Jumper Block	State	Description
JP1	Open/Shorted	Address bit 0 high/low
JP2	Open/Shorted	Address bit 1 high/low

 

User Outputs
Header Name	Pin Name	Description
J2	CT	Critical Threshold Output
J3	INT	Interrupt Output

By default, the PmodTMP2 collects data with 13 bits of resolution including the sign bit. Users may calculate the corresponding decimal temperature by reading the 13 bits (with the most significant bit as the sign bit) in a two's complement format and dividing by 16 (for 13-bit resolution). Thus, one equation that could be used to determine the measured temperature could be:
  * The 2¹² comes from the fact that there are 12 bits of integer data in the 13-bits of resolution.

Any external power applied to the PmodTMP2 must be within 2.7V and 5.5V; however, it is recommended that Pmod is operated at 3.3V.
 

Physical Dimensions
 

The pins on the pin header are spaced 100 mil apart. The PCB is 1 inch long on the sides parallel to the pins on the pin header and 0.8 inches long on the sides perpendicular to the pin header.