Units

The communication database allows to specify units to be used in communication payloads. These units are named wrappers around a base type. They are declared in the units.csv file. The file consists of a csv table with 3 columns and a heading row, containing the names of each column:

Colum name	Column description
Name	The name of the unit type. This name can be used where a type is required.
Type	The underlying base type of this unit. Only raw types, no arrays are accepted.
Description	A human readable description of this unit.

Variants

Units can have variants, which are datatypes representing the same unit but with a different underlying data type. In the communication database, these don’t have to be a defined explicitly in the units.csv file. Whenever it is possible to use a unit, one can instead give a base type with one of the defined units in parentheses.

As an example, given the following units.csv file, which defines a unit1 unit:

Name,Type,Description
unit1,double,A demonstration unit.

One can define and use a variant, for example as a telemetry argument:

Name,Type,Description
datapoint1,float (unit1),Some datapoint for the demonstration.

These variants show up in the units dictionary of the communication database as additional units with different base types in the list after the base unit.

>>> from ecom.database import CommunicationDatabase
>>> database = CommunicationDatabase(...)
>>> database.units['volt']
[
    Unit(type=<class 'float'>, name='volt', baseTypeName='double', description='Voltage.', default=None),
    Unit(type=<class 'float'>, name='volt', baseTypeName='float', description='Voltage.', default=None),
]

On the embedded side, the two units are two different types:

volt_t baseUnitValue = volt_t(0);
voltFloat_t variantUnitValue = voltFloat_t(0);