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Writing to SD card on 9802 from FPGA vi

Exactly.  In fact, this Knowledge Base will work our great for you : How Can I Transfer My Fixed-Point Data Using a FIFO or Memory in LabVIEW 8.5.x? however, instead of the DMA FIFO you'll be using the Write and Read Methods of the NI 9802 to get the data back into Fixed Point or later on reading the data on a Host machine from the SD card.  That combined with the modfied loops in your application should allow you to get the rates you wanted on the FPGA.


Glad to see your on the right track now.

Message Edited by Bassett Hound on 12-08-2008 07:08 PM
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Message 11 of 14

Basset Hound,

You mention below that you have a VI for converting the binary data to fixed point data. Would it be possible to get a copy of this?

My application is recording FXP data in FPGA on the SD card and then retrieving it from the real-time controller.


As a simple test in the PC host domain I have tried to convert a fixed point variable from a front panel control to a boolean array, and then U32, and finally a fixed point variable in an indicator with the expectation of seeing the same value in the control and indicator. But alas no! The blocks I am using are:


- Fixed Point Control

- Number To Boolean Array

- Boolean Array To Number (U32)

- To Fixed-Point

- Fixed Point Indicator


The indicator shows the saturated value of the Fixed Point range which is 0.03125.

For the FXP data type encoding I'm using:

- Signed

- Word Length: 21 bits

- Integer Word Length: -4 bits


This results in a range of -/+0.0312 in the range section of the control properties dialog.

Due to the conversion I'm doing binary 1 ends up being larger than 0.0312 which is why I'm getting the saturated value of the fixed point range.

Possibly your VI will shed some light on this.




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Message 12 of 14

Bassett Hound wrote:


How Can I Transfer My Fixed-Point Data Using a FIFO or Memory in LabVIEW 8.5.x? 


Hi cdsi385,

the linked KB shows how you can do what you need and it works.



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Message 13 of 14


I want my analog data to be written to an SD card using a single channel, as I am new
to Labview I am first using a single analog input channel of NI9215 using FPGA mode.
As I am interseted in using the DMA FIFO(Target to Host) and the analog data which I
am using is taken from a sound source.
I have gone through various discussions some say DMA only takes U32 format data so to
use DMA whether I have to convert the data to U32 format or what? some say that I have
to convert the FXP point data to binary values while writing it to SD card and now I
am confused about how to write the data to SD card.
Once the data is written to the SD card I want to read that data in a way that I want
to play as a recorded sound(audio)
Which FILE I/O method shall I use to record my data and retrieve that data as

I am attaching my VI for review. Kindly help me as I have spent much time on it and
could not find the solution to it.

Best Regards,

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Message 14 of 14