Hi,
(Yet Another Wimborne Model Town Question) :-)
The system design for the WMT River System Water Sustainability Programme
(that really is its name) is progressing slowly and we have tentatively agreed
on a number of things.
The control system will be a distributed network of Raspberry Pis,
interconnected by Ethernet cable (we are trialling Power over Ethernet to see
if we can power the remote devices without needing mains local to them).
Each device will be responsible for taking one or more measurements of water
depth, flow, etc and, in certain locations, for controlling pumps. My question
is about distributing data (eg measurements and speed demands). There will be
a master controller orchestrating everything, so we need to get measurement
data from the Remote Pis to the Master Pi and possibly pump speed demands the
other way.
As a systems engineer my instinct is to use a central database which each of
the Pis can write to or read from. So for example, a level measurement value
gets written to a record and the Master Pi reads that record to use when
determining if a pump speed needs to be changed. The Master Pi then writes
the speed demand to another record, which the Remote Pi reads and acts upon.
My reasoning for selecting a database is that there won't be problems if a
Remote Pi is trying to write to a record at the same time as the master is
tring to read it, plus, I believe that it should be possible to do all these
transactions over the Ethernet link.
However, my knowledge of database functionality is very much at the systems
level, so before I embark on a programme of research, does anyone have any
comments on this approach? If there is a better way, I'd like to hear about
it.
--
Terry Coles
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