Siemens Logo is a moderately priced PLC solution that can be expected
to work over decades (my initial installation worked for 20 years).
I do not expect most Zigbee devices to live that long. So my interest
in combining Logo and HA/Zigbee is huge. And it works fine. But on both
sides there are some shortcomings that lead to unwanted complexity…
HA and Logo have great support for modbus. But the real problems are:
-
In a Logo world you would use buttons e.g. ‘click’ events to
control your lights. -
In HA your would use switches e.g. ‘states’.
-
On the Logo side your ‘click’ events will toggle flip-flops or
trigger more complicated things (multiple lights by a single
button, e.g. double click and hold down). -
On HA the switches have an on/off state which is visualized
on dashboards. -
Both sides must be synchronized, a state changed inside Logo
must get known by HA and toggling a HA switch must generate a
state change inside Logo. -
On the Logo side you will use custom logic blocks, at the HA
side automations. -
HA Modbus support cannot use ‘verify’, which provides a one
way synchronization only because Logo is a bit limited … -
Supporting many switches and their automation becomes a pain.
In Logo some modbus bits (coils) can only be read and some can
only be written. In general you cannot reset a flag that HA has
set from inside Logo. In other words: HA must do so via automation.
As said before this works fine but adds unwanted complexity …
This leaves some questions:
(1) Could there be some ‘writeback’ functionality added to the
modbus switch ‘verify’? So that after a state change detected
by ‘verify’ the state can be written back to the Logo side?
(2) Is anyone interested in this topic at all? I could publish
my solution (custom logic blocks for Logo and a tool to
generate HA entities and automations) and some documentation.
(3) Should I dare to make this text an ‘issue’ at github as a
‘feature request’?
Jürgen