Blackboard's Temperature Sensor

Background information for Blackboard's NXP LM75BDP Temperature Sensor


The Blackboard contains an NXP LM75BDP I2C temperature sensor that is connected to ZYNQ’s I2C0 controller (the I2C bus can run up to 400KHz). The temperature-to-digital sensor includes a band-gap temperature sensor, a sigma-delta analog-to-digital converter, and an I2C controller. The LM75B records an 11-bit 2’s compliment data value, giving it a resolution of .125 °C in the -55 °C to +125 °C range.

Several configuration registers are available to configure various operating modes, but on reset they default to values that configure the sensor to respond to temperature read requests at I2C address 0x1001000. The upper 11 bits of the 16-bit (2-byte) temperature value that can be read from that address contain the temperature value, and the lower 5 bits are not used. The most significant bit is the sign bit, and the remaining 10 magnitude bits must be multiplied by the resolution value (.125) to convert to a temperature value.

Refer to the BBPR or the LM75BDP data sheet for more information.