I have an FPGA VI running on a cRIO 9068 which puts samples from four channels of a 9205 ADC into a Target to Host DMA FIFO. The host VI runs on a Windows machine and (among other things) writes the samples to a TDMS file. I appear to have that working successfully at 1KHz. The host VI is also running a Modbus TCP Master VI which communicates with an Emerson VFD. Its max polling rate is about 250ms.
What I'm currently having issues with is how best to combine these two data sources (the fifo stream and one-dimentional data from the Modbus VFD) into the data array that's being fed into the TDMS write block. My current approach is to convert the fixed point data from the FIFO to doubles. This is then fed to a Decimate 1D Array block to split each channel of data from the FIFO into individiual "appended arrays". The four outputs from the Decimate 1D Array block feed directly to a Build Array block. Currently the Build Array block has 5 inputs - four from the preceeding Decimate 1D Array block, and a 5th that's from the Modbus data (happens to currently be RPM).
Here's the issues I'm having:
If I try to directly feed in the Modbus data into the Build Array block the block changes its output type from a 2D array to a 1D array. Presumably the block defaults to the "lowest common denominator", which is the single input value from the modbus data. My next attempt was to use a Type Cast block and convert the modbus value to an "appended array". This "works", in that Labview doesn't complain, but in the resulting TDMS file the modbus variable is mostly zero, and will only ocassionally be written as a (proper) non-zero value. Obviously the typecast to an array results in mostly zeros.
So my question is:
What is the proper way to combine this stream of data from the fifo with "regular" one dimentional data?
In the attached VI the TDMS Loop is the one in question.
Thanks!
Jesse Dosher
Senior Electrical Engineer
Applied Physics Lab, University of Washington
