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FogLAMP C++ "delta" filter passes deltas of reading data, i.e. repeated values that are the same are not sent after the initial instance of the value.
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FindFogLAMP.cmake FOGL-1915 - revamp of delta filter Dec 6, 2018
LICENSE FOGL-2785 Correct company name in license file May 13, 2019
Package RPM packaging May 15, 2019
delta_filter.cpp FOGL-2297 Update DeltaMap when configuration changes Jan 11, 2019
mkversion FOGL-2338 Support external VERSION file Jan 24, 2019
plugin.cpp Merge pull request #9 from foglamp/FOGL-2338 Jan 25, 2019


FogLAMP delta Filter

FogLAMP "delta" filter passes deltas of reading data. A new reading is only sent onwards if the value of one or more data points in the new reading differs from the previous reading sent by the specified tolerance percentage.

By defining a minimum rate it is possible to force readings to be sent at that defined rate when there is no change in the value of the reading.

Rates may be defined as per second, per minute, per hour or per day.

Configuration items

The following configuration items are supported:

The percentage tolerance when comparing reading data. Only values that differ by more than this percentage will be considered as different from each other.
The minimum rate at which readings should be sent. This is the rate at which readings will appear if there is no change in value.
The units in which minRate is define (per second, minute, hour or day)


Send only readings that differ by more than 1 percent from the the previous reading sent or at a rate of one reading every half hour if the change is less than this.

per hour


To build FogLAMP "delta" C++ filter plugin:

$ mkdir build
$ cd build
$ cmake ..
$ make
  • By default the FogLAMP develop package header files and libraries are expected to be located in /usr/include/foglamp and /usr/lib/foglamp
  • If FOGLAMP_ROOT env var is set and no -D options are set, the header files and libraries paths are pulled from the ones under the FOGLAMP_ROOT directory. Please note that you must first run 'make' in the FOGLAMP_ROOT directory.

You may also pass one or more of the following options to cmake to override this default behaviour:

  • FOGLAMP_SRC sets the path of a FogLAMP source tree
  • FOGLAMP_INCLUDE sets the path to FogLAMP header files
  • FOGLAMP_LIB sets the path to FogLAMP libraries
  • FOGLAMP_INSTALL sets the installation path of Random plugin
  • The FOGLAMP_INCLUDE option should point to a location where all the FogLAMP header files have been installed in a single directory.
  • The FOGLAMP_LIB option should point to a location where all the FogLAMP libraries have been installed in a single directory.
  • 'make install' target is defined only when FOGLAMP_INSTALL is set


  • no options

    $ cmake ..

  • no options and FOGLAMP_ROOT set

    $ export FOGLAMP_ROOT=/some_foglamp_setup

    $ cmake ..


    $ cmake -DFOGLAMP_SRC=/home/source/develop/FogLAMP ..


    $ cmake -DFOGLAMP_INCLUDE=/dev-package/include ..


    $ cmake -DFOGLAMP_LIB=/home/dev/package/lib ..


    $ cmake -DFOGLAMP_INSTALL=/home/source/develop/FogLAMP ..

    $ cmake -DFOGLAMP_INSTALL=/usr/local/foglamp ..

Packaging for 'delta' filter

This repo contains the scripts used to create a foglamp-filter-delta Debian package.

The make_deb script

Run the make_deb command:

$ ./make_deb help
make_deb [help|clean|cleanall]
This script is used to create the Debian package of FoglAMP C++ 'delta' filter plugin
 help     - Display this help text
 clean    - Remove all the old versions saved in format .XXXX
 cleanall - Remove all the versions, including the last one

Building a Package

Finally, run the make_deb command:

$ ./make_deb
The package root directory is   : /home/ubuntu/source/foglamp-filter-delta
The FogLAMP required version    : >=1.4
The package will be built in    : /home/ubuntu/source/foglamp-filter-delta/packages/build
The architecture is set as      : x86_64
The package name is             : foglamp-filter-delta-1.0.0-x86_64

Populating the package and updating version file...Done.
Building the new package...
dpkg-deb: building package 'foglamp-filter-delta' in 'foglamp-filter-delta-1.0.0-x86_64.deb'.
Building Complete.

Cleaning the Package Folder

Use the clean option to remove all the old packages and the files used to make the package.

Use the cleanall option to remove all the packages and the files used to make the package.

You can’t perform that action at this time.