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FPGA Array Comparison by element wierdness

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I have an application where I am comparing limits to the input values from two strain cards (NI-9237) inside an FPGA which is doing some signal conditioning for a sub-system in a larger machine.

 

Process limits are sent from the RT as an array and compared against an input array of "raw" data-

 

Input Data-

FPGA Input.PNG

 

Limit Comparison-

FPGA Compare.PNG

 

 

I am doing a by element to "OR array" and I realize that this may or may not be more effiecient as a compare aggregates; however, the strange thing that is happening is that the sixth element in the limit array is triggering a "Load Error" for the fifth element in the input array. 

 

I am sending the limit directly from the FP of the RT-

RT Set Limit.PNG

Notice that the calculation checked by reading back the value that was set in the FPGA. This set and get seem to line up here. IE, if you set element 3 in either MaxLoad% or LCNominal(mV/V), it is validated on the FPGAMaxLoad output. I am wondering if this has anything to do with the implicit conversion between single floating point to fixed point?

 

If anyone else has experienced this, I would appreciate the feedback on what is happening.

 

I really don't want to go down the DMA route since this is a very small array of six elements an it seems over kill to use up a DMA channel just for this operation.

 

Thanks,

Drew


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