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Version 0.92 release notes

Summary

This is an evolutionary release that introduces modifications to the way the node works to accommodate changes to the sensor hardware in the middle and bottom layers of the GrowCube. It also introduces some new features as described below.

  • Local log files: The node now stores a local record of its operation in a sequential series of files in a directory called logs on the SD card. These can be examined by removing the SD card and viewing the files with a text editor.
  • Options menu: This release includes features that require user interaction. These can be selected using a menu that appears on startup.
  • Manual pH readings: After testing, it was found that the pH sensors interfered with the readings from the other sensors when powered. This particularly affected the EC sensors. This has been resolved in hardware by introducing a switch to select between the pH and EC sensors in the lower two layers of the GrowCube. This was not possible for the top layer because the hardware had already been sent out. PH readings now have to be taken manually (see the sensor documentation pages). It was also found that the best results were obtained when calibration was carried out before every pH reading. The procedure for this has now been built into the firmware.
  • Temperature probe identification: The way in which the substrate temperature probes work means that they were not always recognised in the correct order (i.e. top, middle, bottom). To mitigate this, a local identification procedure has been introduced (see the sensor documentation pages for guidance).
  • Configuration mode: The introduction of the options menu provided an opportunity to make getting into configuration mode easier. This is now possible by choosing the appropriate option on the menu. The previous method of pressing the control button three times still works.

Known issues/limitations

  • Date and time: The node currently attempts to obtain the date and time from the wifi network. Setting the date and time in configuration mode therefore has no effect.
  • Battery indicator: The battery indicator has been disabled. The plan is to reinstate it in a later release.
  • Top-layer sensor readings: Because it was not possible to modify the top-layer sensor unit to add a switch, the sensitivity of the pH and EC sensors at that layer is reduced compared to the other layers.
  • EC sensor calibration: Currently, only generic calibration factors are applied to the EC readings. Local calibration is required before the data can be relied upon. This will be introduced in the next release.
  • Temperature compensation: PH and EC sensor readings are affected by changes in temperature. The current code does not apply temperature compensation. This will be included in a later release; however, the adjustments will be small within the temperature range expected in the GrowCubes. Any gains in accuracy with temperature compensation are likely to be negligible.
  • Log files: Although log files are now created, they are difficult to access. In a later release, the code will be modified so tht the log files are automatically uploaded to the server so that they can ve viewed in the Dandelion app.
  • Options menu: The options menu appears on startup regardless of whether that is the result of a manual reset or waking up automatically from deep sleep. It will be suppressed in the deep sleep case in a future release.
  • WPA2 wifi support: Some local authorities employ the WPA2 Enterprise wifi authentication method which requires a username and password to join the network. This is not currently supported but will be investigated for a future release. In the meantime, the workaround is to use a mifi device or a mobile hotspot as suggested on the Configuration page.
  • Removal of moisture sensor: Support for the moisture sensor has been removed in this version to avoid further interference with other analogue sensors. If it would be convenient, the sensor itself can be removed from the top layer unit by cutting the wires or by opening the enclosure and unplugging the sensor from the circuit board.