#1040 nHaystack Point Write Fallback

Leroy Simms Mon 20 Feb

I would like to write to a Niagara proxy point at say level 9 through Haystack, but if the Haystack connection goes offline the proxy point falls back to the next higher write such as control logic in level 10.

I have no problem writing to the point; however, if I take my Haystack server offline the Niagara point stays at whatever value was last written to at level 9. Does anyone know how to make the value go stale or clear out over a period of time and revert the next available priority?

Richard McElhinney Mon 20 Feb

Hi Leroy,

This is a function of how the Niagara Control Point framework operates rather than nhaystack.

When you set a point at level 9, not only is the value set but the status of the in9 slot is set to Ok.

For the priority array to fallback to the next valid level you need to set the status of the in9 slot to null. When this happens, even if there is a value at in9, the control point will fallback to the next valid level. Obviously if you want this to happen when the connection goes down nhaystack can't do this for you, it needs to happen on the Niagara side.

I suggest that you might need some custom logic on the Niagara side to detect the status of the Haystack connection and set the status of the control point to null when the connection goes down.

Let me know if that makes sense or helps.

Cheers, Richard

Leroy Simms Tue 21 Feb

I had a feeling that might be the case, but was hopeful there was a simple way to set some tuning policies like on a field bus.


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