FPGA Timekeeper 1.1b0.zip

[TylerK]

Known Issue - FPGA Timekeeper 1.1b0

The "LabVIEW Time to FPGA Time.vi" casts LabVIEW time to double precision floating point. This results in loss of precision when converting to FPGA time: NI TimeSync: FPGA Timekeeper 1.1b0 library precision error - NI Community

Attached "FPGA Timekeeper 1.1b1.zip" resolves this issue by using extended precision floating point numbers.

Note: The updated version of "LabVIEW Time to FPGA Time.vi" is saved in LabVIEW 2021.

[Michele__]

Hello Drich,

I have this topic to understand

I have 1 crio chassis (9045) and I want to manage acquisition of channels by this way

1)  fixed crio module channels acquired using DMA FPGA. channels read using FPGA IO node under FPGA target

2)  variable module channels acquired using DAQmx (temperatures, flow meters, force sensors). channels data read from DAQmxunder RealTime side

i'm able to manage acquisition from DMA and DAQmx in the same timed loop, but i need to understand how to synch timestamp information: I want to provide timestamp t0 that comes from DAQmx (DAQmx read waveform array n channels n samples) to samples of FPGA Channels

can I do it using FPGA Time keeper API to synch FPGA time to Realtime time?

best regards

Michele

[CyGa]

Hi Mchele,

The timekeeper won't really help you to sync your FPGA on the DAQmx clock.

However, what the FPGA timekeepr does is to get its original time from the RT controller. Then it keeps it and update it on the FPGA side.
Compared to the clock on the RT side, the clock on the FPGA side is way better and is less prone to shift.

So what you could do is get the time on the FPGA side and associated a FPGA timestamp to the FPGA data that you push inside your DMA.

You would then be able to align your DAQmx samples with your FPGA samples.
I've never used DAQmx on RT, so i don't know where the tiemstamp of the data comes from though. So there is a risk taht you might comapred time coming from 2 clocks that are shifting one from the other...

Maybe taking a look at TSN would help a bit better ?

TSN time is accessible from the FPGA. And I wonder if DAQmx on RT side is also disciplined by the TSN clock...

However with TSN you'd need a reference time clock (another cRIO for example or a master clock).

[Michele__]

Hi Cyril,

Do you know if there is a way to synch the clock of DAQmx and the clock of FPGA? 

I know something about TSN (used for PXI + cDAQs + NI PXI-6683H ) but now my sistem is only 1 chassis, I would like to setup an Hybrid acquisition DAQmx+FPGA 

thank you a lot

Best regards

Michele

[CyGa]

Hi Michele,

Nope I don't know.
I actually never used DAQmx on RT. I always go the FPGA route for all my signals.

[Michele__]

Hi Cyril,

this is what I want to do! Now is clear

It is not timestamp synch what I need. I need DAQmx provide data only when FPGA provide data, so clock syncronization.

It solved  my request:

Solved: FPGA and DAQ card synchronization - NI Community

thank you!