MCP9808 Temperature Sensor
This sample application periodically (0.5 Hz) measures the ambient temperature. The result is written to the console.
If triggered measurements are enabled the sample initializes and maintains a ±2° C window around the current temperature. When the temperature moves outside the window an alert is given, and the window is moved to center on the new temperature.
The MCP9808 digital temperature sensor converts temperatures between -20° C and +100° C to a digital word with ±0.5° C (max.) accuracy. It is I2C compatible and supports up to 16 devices on the bus.
The MCP9808 is available in a discrete component form but it is much easier to use it mounted on a breakout board. We used the Adafruit MCP9808 Sensor breakout board.
Building and Running
After providing a devicetree overlay that specifies the sensor I2C bus and alert GPIO, build this sample app using:
# From the root of the zephyr repository west build -b particle_xenon samples/sensor/mcp9808 west flash
Note that in the capture below output from the trigger callback and the main thread are interleaved.
*** Booting Zephyr OS build zephyr-v2.1.0-537-gbbdeaa1ae5bb *** Alert on temp outside [24500, 25500] milli-Celsius Trtrigger fired 1, temp 15.9375 C iggAlert on temp outside [15437, 16437] milli-Celsius er set got 0 0:00:00.017: 15.9375 C 0:00:02.020: 16 C 0:00:04.022: 16.125 C 0:00:06.024: 16.1875 C trigger fired 2, temp 16.3125 C Alert on temp outside [15812, 16812] milli-Celsius 0:00:08.027: 16.3125 C 0:00:10.029: 16.375 C 0:00:12.032: 16.5 C 0:00:14.034: 16.5625 C 0:00:16.037: 16.5625 C 0:00:18.039: 16.625 C 0:00:20.042: 16.6875 C trigger fired 3, temp 16.8125 C Alert on temp outside [16312, 17312] milli-Celsius 0:00:22.044: 16.8125 C 0:00:24.047: 16.875 C