Point libraries

A point library is the data point list of one device type, in its own file, with no connection information in it (contract §3.4, RFC 0004). Device instances reference it and supply only their own address:

[[device]]
name             = "plc-7"
protocol_address = { transport = "tcp", host = "192.168.0.17", port = 502, unit_id = 1 }
points_from      = ["demo-sim"]

This directory ships one library per demo simulator, all named demo-sim and told apart by their protocol directory:

Library	Points of
modbus/demo-sim.toml	the pymodbus simulator
opcua/demo-sim.toml	the demo OPC UA server
canbus/demo-sim.toml	the demo CAN sender (signals from test.dbc)
canopen/demo-sim.toml	the demo CANopen node
profibus/demo-sim.toml	the demo DP slave

They are what the demo configs in /usr/share/tedge-dot/demo/ reference, and the quickest way to experiment: point a [[device]] at an address, add points_from = ["demo-sim"], and you have a working configuration without typing a single point definition.

Libraries are looked up by name under <dir>/<protocol>/<name>.toml, in each directory of the search path, first match winning:

Directory	For
/etc/tedge/plugins/ot/points.d	a site’s own libraries; shadow packaged ones of the same name
/usr/share/tedge-dot/points.d	libraries shipped by a package (this directory, once installed)

Override the path with [connector] point_library_path or, when running from a source checkout, TEDGE_DOT_POINT_LIBRARY_PATH (colon-separated).

Because /etc is searched first, copying one of these libraries there to edit it means the packaged copy stops being used — deliberately, so your edits survive an upgrade. Give it a different name if you want both.

The device type

A library can name the device type its points describe:

[library]
protocol = "modbus"
type     = "acme-meter-v2"

Every device that references the library inherits it (a type on the [[device]] wins), and it is what the device’s parameter set names are derived from — acme_meter_v2_control_parameters rather than modbus_control_parameters. Those names are tenant-wide identifiers in Cumulocity, so without a type two different Modbus device types would claim the same one. It also becomes the thin-edge entity type of the registered child device.

Points choose their group with meta.parameter.group, and a point may name several:

[[point]]
id   = "coil_rw"
meta = { parameter = { group = ["control", "commissioning"] } }

gives ..._control_parameters and ..._commissioning_parameters, both carrying that point — which is how one signal appears on two operator screens without either going stale. The Modbus demo library above does exactly this. See RFC 0005.