80 lines
2.4 KiB
ReStructuredText
80 lines
2.4 KiB
ReStructuredText
.. zephyr:code-sample:: jc42
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:name: JEDEC JC 42.4 compliant Temperature Sensor
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:relevant-api: sensor_interface
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Get ambient temperature from a JEDEC JC 42.4 compliant temperature sensor (polling & trigger
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mode).
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Overview
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********
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This sample application periodically (0.5 Hz) measures the ambient
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temperature. The result is written to the console.
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If triggered measurements are enabled the sample initializes and
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maintains a |plusminus| 2 |deg| C window around the current temperature.
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When the temperature moves outside the window an alert is given, and the
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window is moved to center on the new temperature.
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Requirements
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************
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The sample requires a JEDEC JC 42.4 compliant temperature sensor. The
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sample is configured to use the MCP9808 sensor.
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The MCP9808 digital temperature sensor converts temperatures between -20 |deg|
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C and +100 |deg| C to a digital word with |plusminus| 0.5 |deg| C (max.)
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accuracy. It is I2C compatible and supports up to 16 devices on the bus.
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Wiring
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*******
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The MCP9808, which is a JEDEC JC 42.4 compliant temperature sensor, is
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available in a discrete component form but it is much easier to
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use it mounted on a breakout board. We used the Adafruit `MCP9808
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Sensor`_ breakout board.
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.. _`MCP9808 Sensor`: https://www.adafruit.com/product/1782
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Building and Running
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********************
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After providing a devicetree overlay that specifies the sensor I2C bus
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and alert GPIO, build this sample app using:
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.. zephyr-app-commands::
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:zephyr-app: samples/sensor/jc42
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:board: particle_xenon
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:goals: build flash
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Sample Output
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=============
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Note that in the capture below output from the trigger callback and the
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main thread are interleaved.
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.. code-block:: console
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*** Booting Zephyr OS build zephyr-v2.1.0-537-gbbdeaa1ae5bb ***
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Alert on temp outside [24500, 25500] milli-Celsius
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Trtrigger fired 1, temp 15.9375 C
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iggAlert on temp outside [15437, 16437] milli-Celsius
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er set got 0
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0:00:00.017: 15.9375 C
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0:00:02.020: 16 C
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0:00:04.022: 16.125 C
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0:00:06.024: 16.1875 C
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trigger fired 2, temp 16.3125 C
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Alert on temp outside [15812, 16812] milli-Celsius
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0:00:08.027: 16.3125 C
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0:00:10.029: 16.375 C
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0:00:12.032: 16.5 C
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0:00:14.034: 16.5625 C
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0:00:16.037: 16.5625 C
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0:00:18.039: 16.625 C
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0:00:20.042: 16.6875 C
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trigger fired 3, temp 16.8125 C
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Alert on temp outside [16312, 17312] milli-Celsius
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0:00:22.044: 16.8125 C
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0:00:24.047: 16.875 C
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