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Monitoring and controlling Easy Controls KWL (air exchanger)devices via Modbus/TCP.

Project description

Python module and command line tool to monitor and control the air exchangers of Helios (KWL EasyControls) via their Modbus/TCP interface. It allows for an easy command line handling of the devices and for a smooth integration of those into smart home systems (e.g. Home Assistant).

Important note: The module and the command line tool were created based on the publicly accessible documentation for the EasyControls Modbus/TCP interface and for the Modbus/TCP protocol. They were only tested with a Helios KWL EC 300 W air exchanger. Use them on your own risk.

The tools are distributed under the terms of the 2-clause BSD License.

Installing

EazyCtrl should work with any recent Python 3 interpreters. (It has been tested with Python 3.6).

Use Pythons command line installer pip to install it:

pip install eazyctrl

This installs both, the single file command line tool eazyctrl and the single file Python module eazyctrl.py. Latter you can import if you want to access the functionality from within your Python scripts.

Using as command line tool

All functionality can be accessed through the command line script eazyctrl. In order to get information about the possible command line options, issue

eazyctrl -h

If you want help about a given subcommand, add the subcommand name before the -h option, e.g.

eazyctrl set -h

will list the available options for the set subcommand.

Obtaining the feature list

In order to list the features which you can access through eazyctrl, use the list subcommand:

eazyctrl list

This would return a table containing the feature names, their access flag (read-only or read-write) and the corresponding variable, e.g.:

Feature name                   Access Variable
----------------------------------------------
fan_stage                      rw     v00102
temp_outside_air               r      v00104
temp_supply_air                r      v00105
temp_outgoing_air              r      v00106
temp_extract_air               r      v00107

Note, that not all variables have been mapped to features yet. Those, not in the table can be queried and set by the low-level variable access methods (see below). But whenever a named feature is available for a given variable, it is recommended to use the more convenient and more robust access via the feature.

Getting the value of a feature

Use the get subcommand to query the value of a given feature.

For example, to query the temperature of the outside air, issue:

eazyctrl get helios-kwl.fritz.box temp_outside_air

The first argument is the host name of the remote device (or its IP-address), followed by the feature name. The result is printed on the console, like:

23.3

Setting the value of a feature

Use the set subcommand to set the value of a given feature.

For example, in order to set the fan stage to level 2, issue:

eazyctrl set helios-kwl.fritz.box fan_stage 2

If the script returns without error message, the communication with the device was successful.

Getting the value of a variable

The command line tool allows to query a variable directly by using its name. This direct variable accesss should only be used, if the given variable has not been mapped to a feature yet.

Additionally to the name of the variable, you also have to provide the maximal length of the expected answer (which can be looked up in the EasyControls manual).

For example, to query the fan stage by reading the variable v00102, issue

eazyctrl getvar helios-kwl.fritz.box v00102 1

Setting the value of a variable

The command line tool allows to set a variable directly by using its name. This direct variable accesss should only be used, if the given variable has not been mapped to a feature yet.

Note, that the value you provide for the variable must be exactly in the right format since it is passed unaltered to the remote device. Consult the EasyControls manual about the expected format for each variable.

For example, to set the fan stage directly via the v00102 variable, issue

eazyctrl setvar helios-kwl.fritz.box v00102 1

Using as a Python module

The functionality of EazyCtrl can be accessed using the eazyctrl Python module. The module can be imported in the usual way

import eazyctrl

The high level class EazyController provides an access similar to the command line tool.

Obtaining the feature list

The static method get_feature_list() returns the available features. It returns a list of tuples, each one containing the name of the feature and a dictionary with various parameters of that feature.

For example the snippet

host = 'helios-kwl.fritz.box'   # replace with the IP-address of your device
ftrlist = eazyctrl.EazyController.get_feature_list()
print(ftrlist)

results in

[('fan_stage', {'rw': True, 'varname': 'v00102'}),
 ('temp_outside_air', {'rw': False, 'varname': 'v00104'}),
 ('temp_supply_air', {'rw': False, 'varname': 'v00105'}),
 ('temp_outgoing_air', {'rw': False, 'varname': 'v00106'}),
 ('temp_extract_air', {'rw': False, 'varname': 'v00107'})]

Getting the value of a feature

The method get_feature() returns the value of a given feature. The value is converted to an appropriate Python type (e.g. integer, float, etc.).

The following example queries the value of the outside air temperature sensor

host = 'helios-kwl.fritz.box'   # replace with the IP-address of your device
ctrl = eazyctrl.EazyController(host)
temp_out = ctrl.get_feature('temp_outside_air')
print(temp_out, type(temp_out))

This results in

24.4 <class 'float'>

Setting the value of a feature

You can use the set_feature() method to set a value for a given feature. You should provide the value as a Python type (e.g. integer, float, etc.) and it will be automatically converted to the right text representation before being passed to the device.

For example, you can set the fan stage to level 3 by the following snippet:

host = 'helios-kwl.fritz.box'   # replace with the IP-address of your device
ctrl = eazyctrl.EazyController(host)

# Setting the fan stage
success = ctrl.set_feature('fan_stage', 3)
print(success)

# Querying the fan stage to check, whether it has the desired value now
fan_stage = ctrl.get_feature('fan_stage')
print(fan_stage)

The set_feature() method returns True or False indicating whether the communication with the device was successful or not. So, for the snippet above, you should get the output

True
3

and of course, the fan should have been switched to stage 3.

Getting the value of a variable

Similar to the command line tool, the EazyController object allows direct variable access as well. This low-level function returns the response of the server unaltered as a string, unless you specify a conversion function. Beyond the variable name, you also have to pass the length of the expected answer (to be found in the EasyConfigs manual).

Let’s query the outside air temperature via the v00104 variable and convert it to a float value

host = 'helios-kwl.fritz.box'   # replace with the IP-address of your device
ctrl = eazyctrl.EazyController(host)
temp_out = ctrl.get_variable('v00104', 7, conversion=float)

Setting the value of a variable

Via the set_variable() method you can set the value of a given variable.

The example below, sets the fan stage using the variable v00102. It also demonstrates, that you can use a formatting string instead of a conversion function for the conversion argument:

host = 'helios-kwl.fritz.box'   # replace with the IP-address of your device
ctrl = eazyctrl.EazyController(host)

# Setting the variable
ctrl.set_variable('v00102', 3, conversion="{:d}")

# Check, whether the variable contains the right value
fan_stage = ctrl.get_variable('v00102', 1, conversion=int)

print("Expected: {:d}, obtained {:d}".format(3, fan_stage))

If everything went well, you should obtain

Expected: 3, obtained 3

Notes on concurrent access conflicts

Due to its design, the EasyControls protocol can not deal well with concurrent accesses of multiple clients. Especially, reading out a variable/feature is very error-prone as it needs two communications. The first communication tells the server, which variable should be queried, while the corresponding variable value is returned during the second communication. If between the first and second communication a second client starts a query for a different variable, the first client may get back the value for the wrong variable (namely the one the second client asked for).

When EazyCtrl detects, that the wrong variable was returned, it will repeat the given query again after a short random time delay (maximally 3 times). While this strategy should be enough to resolve concurrent access conflicts in typical use cases, it may fail if too many clients / threads are accessing the device at the same time.

Therefore, always try to make sure, that only a single client is accessing the device at a time.

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