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Do the devices support the “Read/Write Property Multiple” services or must each property be read in a separate message.
Find
the answer to this question by reading the BIBs statement for each
device or you could explore the device object of the device, find the
property called BACnetServicesSupported and then look at the 14th item
in the array to see if Read Property Multiple is supported and the 16th
for Write Property Multiple. However, we have found that a large number
of devices don’t display this information.
Obviously, if you can read a chunk of properties in one message you will be better off than if you can only read a single one.
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Can you use BACNet’s COV mechanism.
COV stands for Change of Value. When a device supports COV another device /
application can subscribe to receive notifications when an object
property changes. This means the data client doesn’t have to poll for
data continuously but can wait passively to be notified of the change.
This reduces the number of messages on a network dramatically.
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Some devices are slower than others.
BACnet
allows up to 15 msec for a device to use the token. Since most messages
on a MSTP network are token passes a device that uses the token in 5
msec will consume much less bandwidth than one that takes 15msec. (A
number of vendors relax this requirement to allow for other vendors
implementations. The more relaxed the more bandwidth is consumed doing
nothing.)
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