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Transfer FPGA clock value to Host

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Good morning to everyone,

I have a simple question, that is however quite annoying for me.

In brief, there is a way to transfer the value of the FPGA clock to the host, in order to do some calculation on the host itself? Actually i tried with read/write control but it seems not working.

Thanks!

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Hi ALST,

 

In brief, there is a way to transfer the value of the FPGA clock to the host, in order to do some calculation on the host itself?

You can transfer any data from FPGA to host…

What exactly is that "value of the clock"?

 

Actually i tried with read/write control but it seems not working.

What have you tried?

What does not work? In which way does your code not execute as expected?

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Hi GerdW,

So, I should detail better my question, I'm sorry that I wasn't clear.

I am trying to transfer the Clock frequency of the FPGA, so for example 40 Mhz. This value appears in the fpga block diagram as a I/O source control that I connect to the Single Cycle Timed Loop input source.

Usually, when I want to read a variable on the Host side, I put an indicator on it on the FPGA side, and then I use read/write on Host. Well, in this case, the read/write doesn't find this indicator (as it doesn't exist) and I'm not able to read it.

Thanks again,

ALST

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Hi ALST,

 

I put an indicator on it on the FPGA side, and then I use read/write on Host. Well, in this case, the read/write doesn't find this indicator (as it doesn't exist) and I'm not able to read it.

Either there is an indicator and you can read it from the host - or there isn't an indicator.

When the indicator doesn't exist then you need to create it!

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Well,

I have an indicator indeed on the FPGA clock, but on the host side it doesn't appear.

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Attach a simplified version of  your project zipped up in a .zip file.

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Message 7 of 13
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Hi ALST,

 

why do you need the clock rate explicitely as indicator in your FPGA?

It's a setting done at edit time, so you KNOW how long each iteration takes…

 

Your problem (probably) comes from the fact you try to transfer a reference from FPGA to RT host, but that reference becomes pointless in the host…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Hi GerdW,

I need the valuea of the clock because I had two or three derivated clocks, and when I choose among them I want the Host to be ware of this change, since it has to do some calculation with that value.

The point is that I don't understand why every other indicator (on FPGA) can be seen from the read/write control (on Host) while the clock doesn't appear (so I cannnot work with it).

Thanks,

ALST

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Hi ALST,

 

because I had two or three derivated clocks, and when I choose among them I want the Host to be ware of this change

Two options:

1. The selection of the clock is done at edit time of the FPGA VI: then you KNOW the clock speed and can adapt your host too.

2. The clock selection is done at runtime: then you can also select a different value for a simple numeric/enum indicator. Read this indicator from your host…

 

while the clock doesn't appear (so I cannnot work with it).

I guess it's because it is an FPGA-internal reference…

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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