Bug in Defer Panel Update with Chart Value Property

[Karthik_Abiram]

Hi Guys,

When defer panel update property is set to True, and chart is updated using "Value Property" node, data is not getting updated in chart. Screen shot of block diagram and VI (2014) attached. 

Is this a known bug, and is there any fix for it?

Thanks,

Karthik

[Hooovahh]

A common problem people have is where they defer, then an error is passed into the undefer which will not perform the undefer.  This is not the case with your VI but I wanted to make you aware that this is where people usually have problems.

So I tried a few things and I'm not sure why it doesn't work.  But I know you can write to the chart terminal, or a chart local variable instead of the property node and it works as it should.

I'd say bug, but it is a strange one, NI needs to fix it.

[Karthik_Abiram]

Thanks Hooovahh for your reply. Yes, it's a strange bug indeed.

In my use case, I need to update the chart of a VI from another VI, due to which I can't use the terminal or local variable.

[tst · Accepted solution]

I haven't tried running your code, but here are some possible workarounds:

1. There's a primitive for writing a control's value by index (added in ~2013). This is designed to be used from other VIs too and should work like a local.
2. You can send the data using another way (like a queue, etc.).
3. Use the Ctl Val.Set method.
4. Don't use a chart. Use a graph and manage the buffer yourself. You can find some examples if you search for XY chart.

[Karthik_Abiram]

Thanks tst for your helpful alternative suggestions.

Your options 1 & 3 are simpler, and they work with defer panel updates. Option 1(Set Control Value by Index) actually performs better when defer panel updates is not used. VI with all 3 options attached with this mail, for anyone interested in this.

Thanks,

Karthik