METEO

TFM MSEEI Universidad de Malaga

Iván René Morales Argueta - 2018

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ToDo List

Meteo

• Connect to MQTT Broker in object constructor
  • Subscribe to each Settings sub-topic Settings/#
  • (Optional) Show performance and broker info by subscribing to special $SYS topics (https://www.hivemq.com/blog/mqtt-essentials-part-5-mqtt-topics-best-practices)
• Sample each sensor using separate threads
  • Create a generic sampling method (one-shot), which receives the sensor name as parameter
    • sampleSensor (sensorName)
    • Front-end interface variables (i.e. Air Quality, instead of Humidity+Gas_Resistance)
  • Create a thread/method to periodically launch the one-shot sampling method
  • Generate as many threads running this method as required
  • Kill sampling threads during object destruction Destructor not compatible with threaded implementation
  • Implement a mutual-exclusion mechanism to avoid access violations
• Send sensors' data via MQTT using topics to distribute data into different channels
• Each "METEO" station MUST have a vaild (integer type) identifier, starting from 0
• Topics should accomplish with the following template:
  • METEO/<stationNumber>/Data/<sensor>
  • Valid <stationNumber> (identifiers) are integers from 0 to N-1
  • Valid <sensor> values are:
    • Temperature (Environmental temperature) [temp]
    • Humidity (Relative humidity) [hum]
    • Pressure (Local atmospheric pressure) [pres]
    • Light (Incident light measurement) [light]
    • AirQuality (Air quality as pollution measurement) [airQ]
    • PPM (Raw particle count) [ppm] PPM is irrelevant. Instead, PPM field used to transmit raw gas resistance value
• A special topic may be used to set/get the sampling period dymanically
  • METEO/<stationNumber>/Settings/SamplingRate/<sensor>
  • <sensor> field (sub-topic) is the same as described before
  • Sampling rate value must be validated to remain between a valid range
    • Min sampling rate 1 minute
    • Max sampling rate 120 minutes
    • If a sampling rate (SR) out of these limits is set, a default value will be chosen if a prior valid SR wasn't set yet; otherwise, the last valid SR will remain active
• (Optional) A special topic may be used to remotely reboot the device if no Alive beacons have been received
  • METEO/<stationNumber>/Setiings/Reboot
  • A unique key must be sent as password (through Reboot topic) to force a reboot
  • Key will be stationNumber-dependent and time-dependent (unix format) hash
  • Hash must be computed by UI
• A special topic may be used to announce "I'm Alive" messages from stations to broker
  • Invoke it via a separate thread as it may behave as a locking method
  • METEO/Alive
  • Each station should publish a message containing only its <stationNumber> periodically (ie. every 1 minute)

Printed circuit board

• Design a PCB to place the sensor boards and the User-Interaction hardware (push-button + LED)
  • Design must be compatible with Raspberry PI 3 header footprint
  • Power must be supplied from Raspberry PI's 3v3/GND breakout pins
  • Manufacture PCB and test functionality

BME680_METEO

• Compute Air Quality (%) using Humidity and Gas measurements
• Compute PPM using Gas Baseline and Gas measurements Not a requirement. Discarded from further releases.

User Interaction

• Add an LED status indicator to show whether the server is running or not (using RPI-GPIO)
• Add a push-button input to hard-reset the server via a separate thread if anything fails (using RPI-GPIO)

Data management

• Grab sensors' data from MQTT broker and process it to deliver filtered information
• Store the processed data into a SQLite database
• Retreive data from Broker and append it to a table within in the DB (running in parallel thread?)
• Export table's content to a CSV when required
• If several measurements from different sensors retreived within the same MINUTE, store them in the same register row.
• If several measurements form the same sensor retreived within the same MINUTE, average grabbed values and then store the last average computation.

Reliability

• Run meteo.py as a standalone application
  • Set flag to meteo.py
    • chmod +x meteo.py
• Autorun on boot
  • sudo crontab -e
  • @reboot /home/pi/METEO/meteo.py &
• Software Watchdog Timer
  • Run a parallel process (subscribed to ALIVE topic) to check whether METEO is running or not
  • Restart METEO process after 3 consecutive ALIVE periods with no answer
  • Start WDT timer after the first ALIVE message arrives

User interface

• Node-RED User Interface