In this article we look at the TMP102 digital sensor and we will connect it up to a Raspberry Pi
The TMP102 device is a digital temperature sensor ideal for NTC/PTC thermistor replacement where high accuracy is required. The device offers an accuracy of ±0.5°C without requiring calibration or external component signal conditioning. Device temperature sensors are highly linear and do not require complex calculations or lookup tables to derive the temperature. The on-chip 12-bit ADC offers resolutions down to 0.0625°C.
The TMP102 device features SMBus™, two-wire and I2C interface compatibility, and allows up to four devices on one bus. The device also features an SMBus alert function. The device is specified to operate over supply voltages from 1.4 to 3.6 V with the maximum quiescent current of 10 µA over the full operating range.
The TMP102 device is ideal for extended temperature measurement in a variety of communication, computer, consumer, environmental, industrial, and instrumentation applications. The device is specified for operation over a temperature range of –40°C to 125°C.
Download this and rename as .py file extension – tmp102
import time import smbus i2c_ch = 1 # TMP102 address on the I2C bus i2c_address = 0x48 # Register addresses reg_temp = 0x00 reg_config = 0x01 # Calculate the 2's complement of a number def twos_comp(val, bits): if (val & (1 << (bits - 1))) != 0: val = val - (1 << bits) return val # Read temperature registers and calculate Celsius def read_temp(): # Read temperature registers val = bus.read_i2c_block_data(i2c_address, reg_temp, 2) temp_c = (val << 4) | (val >> 5) # Convert to 2s complement (temperatures can be negative) temp_c = twos_comp(temp_c, 12) # Convert registers value to temperature (C) temp_c = temp_c * 0.0625 return temp_c # Initialize I2C (SMBus) bus = smbus.SMBus(i2c_ch) # Read the CONFIG register (2 bytes) val = bus.read_i2c_block_data(i2c_address, reg_config, 2) print("Old CONFIG:", val) # Set to 4 Hz sampling (CR1, CR0 = 0b10) val = val & 0b00111111 val = val | (0b10 << 6) # Write 4 Hz sampling back to CONFIG bus.write_i2c_block_data(i2c_address, reg_config, val) # Read CONFIG to verify that we changed it val = bus.read_i2c_block_data(i2c_address, reg_config, 2) print("New CONFIG:", val) # Print out temperature every second while True: temperature = read_temp() print(round(temperature, 2), "C") time.sleep(1)
Run the above code by typing in sudo python tmp102.py. You should see something like this