Using NI 9215 raw data calculate PSD of signal

[suni]

Hi

I am using C series NI 9215 module to acquire data in FPGA interface mode. In the module, calibration mode is set as raw. I am using DMA FIFO to transfer data from this module to RT host to calculate and display PSD of the signal. PSD graph is showing right frequency but incorrect amplitude because I am giving it raw values. How do i convert those raw values to calibrated values in RT host? Or should i use clibrated data in the FPGA vi ? When i changed the calibration mode of the module to calibrated type data type became fixed point type.Thanks.

[Ipshita_C]

Hi Suni,

Are you trying to caluclate the PSD in your RT VI or in your Windows Host VI? There are only 2 calibration modes available in FPGA--raw and fixed-point. I would convert the data to fixed-point in the FPGA and then transfer it to RT to perform the PSD. Please also look at this link to get a better idea of fixed-point data types in FPGA. Hope this helps.

Ipshita C.

[suni]

Hi

Thanks for the reply. If I use C series NI 9215 module using fixed point calibration then values i am getting from the module is already converted to engineering units right (i mean if module is acquiring 5v signal, digitized value of signal the is also 5v). Thanks.

[Ipshita_C]

Hi Suni,

That is right--when using the FP calibration mode the math to use the calibration information and convert the ADC data to engineering units is already done for you and available on FPGA. 

Ipshita C.

[suni]

Hi

I set my analog input and output modules to calibrated mode. After I did this fpga compilation report gave me timing violation. Does this process affect fpga timing?

[Ipshita_C]

Hi Suni,

Please have a look at the linked knowledgbase articles for switching between the two calibration modes and a better understanding of the fixed point calibration mode. This should help you--the timing error is a compile error and it does affect FPGA timing, to answer your question. 

Ipshita C.