MCP9808 Temperature Sensor on Adafruit breakout board

Microchip's I²C High Accuracy Digital Temperature Sensor



Some quick specs

  • Cheap ($4.95 for complete breakout board)
  • Simple I²C control
  • Up to eight MCP9808 on a single I²C bus with adjustable address pins (see I²C Addressing)
  • 0.25°C typical precision over -40°C to 125°C range (0.5°C guaranteed max from -20°C to 100°C)
  • 0.0625°C resolution
  • 2.7V to 5.5V power and logic voltage range (3.3V typical)
  • Operating Current: 200 µA (typical)
  • Uses any I²C address from 0x18 thru 0x1F
  • Datasheet


Breakout board pinout

    Power pins
  • Vdd - This is the positive power and logic level pin. It can be 2.7-5.5VDC, so fine for use with 3 or 5V logic. Power Vdd with whatever logic level you plan to use on the i²c lines
  • GND - this is the ground power and logic reference pin

    • I²C Data pins
  • SCL - this is the I²C clock pin. There's a 10K pull-up already on the board, so connect this directly to the i²c master clock pin on your microcontroller
  • SDA - this is the I²C data pin. There's a 10K pull-up already on the board, so connect this directly to the i²c master data pin on your microcontroller

    • Optional pins
  • Alert - This is the interrupt/alert pin from the MCP9808. The chip has some capability to 'alert' you if the chip temperature goes above or below a set amount. This output can trigger to let you know. It is open collector so you need to use a pull-up resistor if you want to read signal from this pin
  • A0, A1, A2 - These are the address select pins. Since you can only have one device with a given address on an i²c bus, there must be a way to adjust the address if you want to put more than one MCP9808 on a shared i²c bus. The A0/A1/A2 pins correspond to the Least Significant Bits (LSBs) of the address bits of the i²c address. There are pull-down resistors on the board so connect them to Vdd to set the bits to '1'. They are read on power up, so de-power and re-power to reset the address


I²C Addressing

The default address is 0x18, no address select pin is connected to Vdd.
The address can be calculated by 'adding' the A0/A1/A2 to the base of 0x18
  • A0 sets the lowest bit with a value of 1
  • A1 sets the middle bit with a value of 2
  • A2 sets the high bit with a value of 4
The final address is: 0x18 + A2 + A1 + A0

  Connect pins to Vdd to set the bits to '1'
HEX / Decimal A0 (1) A1 (2) A2 (4)
0x18 (24)      
0x19 (25) 1    
0x1A (26)   1  
0x1B (27) 1 1  
0x1C (28)     1
0x1D (29) 1   1
0x1E (30)   1 1
0x1F (31) 1 1 1


Python

External addresses to Adafruit:
Python & CircuitPython
Python Docs (Adafruit MCP9808 Python Library)


Schematic