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When running the BACnet Proxy and MasterDriver agents, I receive the following error message:

master_driver.driver ERROR: Failed to scrape Device Name: RuntimeError('Device communication aborted: segmentationNotSupported')

Could anyone help me to resolve this error?

Psidom
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Sen
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1 Answers1

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BACnet has a size limit for the size of a message. The message size has several different valid values based on the BACnet specification. If a device wants to send a message that exceeds the supported size of either device it may segment the message into smaller pieces. Both devices must support segmentation for this to work, otherwise you get the error you are seeing.

The cause of this error is the device being scraped does not support segmentation and the number of points being scraped by the driver at once (by default, all of them) creates a message too big to avoid segmentation either sending or receiving.

The BACnet driver currently supports manual segmentation to overcome this device limitation without reducing the number of points configured in the driver. You can set the max_per_request setting in the driver_config section of a BACnet device configuration. The setting is per device so you must include max_per_request in every device affected. A typical value is 20. If the error persists try lower values.

A planned future enhancement for the BACnet driver is to auto detect this case and automatically set an ideal max_per_request value.

EDIT

I should also mention that the max_per_request argument was added after VOLTTRON 3.0. You need to be running either 3.5RC1 or the develop branch.

Kyle Monson
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  • Hey Kyle. Thank you so much for your explanation. I reduced the max_per_request value to 1 but the error was not eliminated. – Sen Aug 15 '16 at 23:35
  • How many BACnet drivers are you running? It needs to go into every configuration for every device affected. I'll edit my response to make that clear. Could you add one of your config files to your question so we can make sure you are doing it correctly. – Kyle Monson Aug 17 '16 at 16:18
  • Also, which version of VOLTTRON are you using? I don't think this feature is in the 3.0 stable version. – Kyle Monson Aug 17 '16 at 16:21