184 lines
8.9 KiB
ReStructuredText
184 lines
8.9 KiB
ReStructuredText
.. _functionality:
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Functionality
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==============
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The main features
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-----------------
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* **Operates in two modes gravity monitoring and configuration mode**
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In ``gravity monitoring`` mode it behaves just like the iSpindle, it wakes up at regular intervals, measures
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angle/tile, temperature, calculates gravity and pushes the data to defined endpoints.
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In ``configuration mode`` the device is always active and the webserver is active. Here you can view the
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angle/tilt values, change configuration, update the gravity formula. When in this mode you can also interact
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with the device via an REST API so data can be pushed to the device via scripts (see API section for more information).
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.. image:: images/index.png
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:width: 700
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:alt: UI example
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You can force the device into ``configuration mode`` while measuring gravity. This is useful when calibrating
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the device so you don't needs to wait for the device to wake up and push the data. The entire calibration
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sequence can be handled via the web interface without need for additional software tools.
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See the :ref:`setting-up-device` section for more information on how to trigger the configuration mode.
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* **Can send data to multiple endpoints**
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The original iSpindle can only have one destination, this software will push data to all defined endpoints so
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in theory you can use them all. However this will consume more battery power so use only as many as needed. Its much
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more efficient to have the endpoints on your local network than on the internet.
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Currently the device supports the following endpoints.
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* http (ssl optional)
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* influxdb v2 (ssl optional)
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* MQTT (ssl optional)
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* Brewfather
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* Home Assistant
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* Brew Spy
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* Brewers Friend
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* Fermentrack
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* Ubidots
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* Thingsspeak
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Under the :ref:`services` section you can find guides for how to connect GravityMon to these services. For a
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description of what data is transmitted you can see :ref:`data-formats`.
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The software support SSL endpoints but currently without CA validation, this means that the data is encrypted
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but it does not validate if the remote endpoint is who it claims to be.
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if you require CA validation please leave a comment on GitHub and I will make that a priority. Adding this function
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will dramatically reduce the battery life of the device.
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.. note::
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Using SSL on a small device such as the esp8266 can be unstable since it requires a lot of RAM to work. And running out
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of RAM will cause the device to crash. So enable SSL with caution and only when you really need it. GravityMon will try
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to minimize the needed RAM but the remote service might not support that feature.
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* **Create gravity formulas on the device**
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Another big difference is that this software can create the gravity formula in the device, just enter the
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angle/gravity data that you have collected. You will also see a graph simulating how the formula would work.
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Currently the device can handle 10 data points which should be enough to get a accurate formula. At least 3 data points
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is needed to get an accurate formula.
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* **Customize the data format being sent to push targets**
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In order to make it easier to support more targets there is a built in format editor that can be used to
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customize the data that is to be sent. This way you can easily adapt the software to new targets without coding.
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If you have a good template please share it on the github repository and I will add it to the documentation
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for other users to enjoy. See the :ref:`format-editor` for more information. See :ref:`services` for a list of
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services currently validated.
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* **Automatic temperature adjustment of gravity reading**
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If you want to correct gravity based on beer temperature you can do this in the formula but here is a nice
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feature that can correct the gravity as a second step making this independent of the formula.
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* **OTA support from webserver**
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When starting up in configuration mode the device will check for a software update from a webserver. This is an easily
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way to keep the software up to date. In the future I might add a hosted endpoint for providing updates. OTA can also be
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done over a SSL connection.
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* **DS18B20 temperature adjustments**
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You can adjust the temperature reading of the temperature sensor. In normal cases this should not be needed since
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the sensors should be calibrated.
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* **Gyro Movement**
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The software will detect if the gyro is moving and if this is the case it will go back to sleep for 60 seconds.
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This way we should avoid faulty measurements and peaks in the graphs.
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* **WIFI connection issues**
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The software will not wait indefinitely for a wifi connection. If it takes longer than 20 seconds to connect then
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the device will try the secondary wifi configuration, and that also fails it will go into deep sleep for 60 seconds and then
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retry later. This to conserve batter as much as possible.
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* **Use gyro temperature sensor**
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This works fine when the device has time to cool down between measurements and it saves up to 400 ms.
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My testing shows that this is quite accurate with a deviation of less than 0.3C. This
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reduces the run time by 20% (with optimal wifi connection).
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The graph below compares from the temp from two different devices in the same bucket of water. One with
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gyro temp enabled and one with the DS18B20 sensor. The blue line is the gyro temperature and this clear
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that the temperature will be higher after it has been running but cools down when in sleep mode. The interval
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has been set to 300s. A low delay of 30s will not allow the gyro to cool down and the temperature will
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be 0.5-1.0C higher.
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.. image:: images/temp1.png
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:width: 800
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:alt: Gyro temp vs DS18B20
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* **Celsius or Fahrenheit**
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You can switch between different temperature formats. GravityMon will always use C for it's internal calculations and
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convert to F when displayed.
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* **SG or Plato**
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You can switch between different gravity formats. GravityMon will always use SG for it's internal calculations and
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convert to Plato when displayed.
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* **Stable gyro data**
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The device will read the gyro 50 times to get an accurate reading. If the standard deviation is to high it will not
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use the data since this is inaccurate and the device is probably moving, probably do to active fermentation or movement of
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fermentation vessel. This sequence takes 900 ms seconds to execute and besides wifi connection this is what consumes the most
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battery. With more testing this might be changes to either speed up or provide more stable readings.
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* **Performance measurements**
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I've also create a small library to measure execution code in some areas of the code that i know is time consuming. This
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way I can find a good balance between performance and quality. This is a lot of help trying to figure out where bottlenecks
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are in the code and where to put optimization efforts. Examples of real measurements:
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* Reading the gyro: 885 ms
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* Reading DS18B20 temperature sensor: 546 ms
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* Connect to WIFI: 408 ms
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* Send data to local influxdb v2: 25 ms
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* Send data to local mqtt server: 35 ms
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* Send data to local http server: 40 ms
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* Send data to http server on internet: 0.2 - 5 seconds
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See the :ref:`compiling-the-software` for more information.
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* **Power measurements**
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I've also create a project to measure the power consumption of the device, but more on this later.
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Battery life
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------------
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The long term battery test has now been completed. Using a 2200 mA battery and sending data every 5 minutes to a local server on my network. The battery lasted 47 days which is excellent battery life.
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In another test I had a device running with an sleep interval of only 30s with ok wifi connection. The device lasted 12 days which i think is excellent considering the short sleep interval.
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From what I have discovered it's the WIFI connection or latency to internet hosted that has the most impact on the battery life. The typical runtime in the tests above was around 2 seconds.
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Performance
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-----------
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Since I have the possibility to measure the performance of different function in the code this is what I have been able to gather.
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The typical runtime in a measurement cycle is approx 2 seconds and in some cases it can take up to 6-8 seconds but this is mainly related to establishing the WIFI connection. So stable wifi is
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essential for long battery life. Out of the 2 seconds of run-time the major time is spent on gyro readings (1.3s) and temperature measurements of (0.6s) so using the gyro sensor for measuring
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temperature would reduce the total runtime with 25%. Sending data over http takes less than 100ms (on my local network) so this is not drawing much power.
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The image below shows how the run-time varies over time. The pink line is the wifi connection time and this is why the time varies. The orange is the total runtime for the awake period.
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.. image:: images/perf1.png
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:width: 800
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:alt: Performance view
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