Issue
A program in bCX or b3 is writing/reading to/from a second device, the write/read operation is not working and the second device is not listed on the list of known devices in the bCX/b3 that has the program.
Product Line
Andover Continuum
Environment
- CyberStation
- BACnet bCX
- b3
Cause
Device is not answering to WHO-IS message.
When a reference is made in a device (A) to a second device (B) a WHO-IS message is sent from A to B, when the I-AM is received the devices is added to the list of known devices.
If no I-AM is received then the device remains unknown and cannot be listed, as a consequence write/read messages (among other things) will fail.
In the screen shot below device b3.810 know about itself and one other device (b3.867).
If a program in b3.810 performs a WriteProperty operation to a third device C, the WriteProperty operation can not succeed until C has been added to the list of known devices via the internal mechanism explained above.
Resolution
Use Wireshark to check whether the device with the reference is sending out the WHO-IS and more importantly whether an I-AM is coming back from the destination device.
In the case that originated this ticket, the destination third party device would not consistently send an I-AM when operating at high baud rate, the MSTP baud had to be lowered to 19200 .
