Issue
What are the data sharing differences between the Wireless Infinet and the Hard Wired Infinet?
Environment
- Wireless Infinet
- Hard Wired Infinet
Cause
Information on what is like to implement a wireless Infinet bus verse wired Infinet bus.
Resolution
Import/Export differences between a Wireless Infinet bus and a Wired Infinet Bus
Below outlines what the differences are between a Wireless Infinet bus and a Wired Infinet bus when it comes to imported and exported values.
Note: A point that is flagged as Exported will send it’s value out on any bus, wired or wireless, only when the point value changes. If the point value keeps changing rapidly, then every time the value changes it will be sent out on the bus. If the point value only changes rarely it still follows the same rule. It will only send the it’s value out on the bus when it changes no matter how often a program calls for the value.
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Programs that create an Import/Export relationship with the format PointA=ControllerB\PointA.
Wired Infinet
In a wired infinet bus when a point that is flagged to be exported changes it’s value it’s value will be broadcast as a single message on the Infinet bus. Any controller that hears that broadcast and has an Import/Export entry for that point will grab the value off the wire and update it’s Import/Export table. If a controller that needs that value does not get it due to Infinet bus problems then that controller will not update it’s Import/Export table and will miss the point value update. Again the above scenario is for a hard wired Infinet bus.
Wireless Infinet
In a wireless infinet bus when a point that is flagged to be exported changes it’s value it’s value will be sent as separate messages to each controller that has in Import/Export entry for that point. For example if a point is used on 10 different controllers and the point is flagged for export and also the point value changes then ten separate messages will be sent out, one to each controller. The for each one of those 10 messages the originating controller is expecting an acknowledgement back from the destination controller. If the sending controller does not get the “ACK” message it will retry sending the message again every 3 minutes until it does receive and “ACK”.
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Programs that cause a re-transmission of a point that is flagged as exported with the format Set PointA Refresh=True.
Wired Infinet
In a wired infinet bus when a program sets the refresh attribute of a point equal to true then it will send out a single broadcast message on the Infinet bus. Any controller that requires that point’s value will grab the message off the bus and update it’s import/export table. This will send the value of the point out onto the bus regardless or whether the point value changes or not.
Wireless Infinet
In a wireless infinet bus when a program sets the refresh attribute of a point equal to true it will send individual messages to each controller that has an Import/Export entry for that point. For example if a point is used on 10 different controllers and the point is flagged for export then 10 separate messages will be sent out on the bus to each of the controllers that require that point value. For each of those 10 messages the originating controller is expecting an acknowledgment back from each of the destination controllers. If the sending controller does not get the “ACK” message it will retry sending the message.
NOTE: In item 2 you need to be very careful if you are using a refresh program. When using refresh programs you do NOT want to make them looping. You especially do not want to make them loop through setting the refresh to true. A simple fall through program that is triggered off the Minute system variable should be fine. Also remember that a refresh program is a workaround for an underlying bus problem. This holds true whether it is a wireless bus or a wired bus. Since Wireless Infinet I/E is a guaranteed delivery, DO NOT use refresh programs in Wireless Infinet. The additional network traffic can choke the network and it is totally unnecessary.
It is also important to put thresholds on exported points to avoid overloading the wireless network. If a wireless point is exported to many other devices, especially on another network whether wired or wireless, you should mirror that point in the BCX and let the BCX distribute it to the other network, by having the other devices reference the mirrored point.
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Alarms being sent to the front end.
Wired Infinet
In a wired infinet bus when a point goes into alarm the alarm message will be broadcast as a single message to the BCX. If there is a problem with the bus, ie substandard installation, grounding problems, etc… , then there is a possibility that the alarm message does not make it to the BCX controller.
Wireless Infinet
In a wireless infinet bus when a point goes into alarm the alarm message will be sent as a point to point message to the BCX. If the sending controller does not get an “ACK” message from the BCX then the controller will retry sending the message again every 3 minutes until it does receive an “ACK” message from the BCX.
Important note: Any point that has an alarm attached is tagged for export. This means that every change of the point's value will cause an export, even if the point is not in alarm. If you have points that change their value often you need to put a threshold on these points even if they only have an alarm attached on a wireless Infinet to avoid excessive traffic.
