NI USB 8451 SPI READ

[James_Creation]

I have a question about using NI 8451 USB Module for data exchange with a 16-bit ADC CS5501.

This ADC CS5501 has only CLK & DATA OUT pins. If there is no MOSI connection between the 8451 and the ADC CS5501, can we get the data out from the ADC after we send signals of chip selection, SCLK, and MOSI which is required according  to 8451’s specs (if we need to get 2 bytes from the ADC, we have to send out 2 bytes dummy data via MOSI)?

Thanks a lot,

James

[alyssa.h]

Hey James_Creation,

Would it be possible for you to attach a link to the product page or manual for the ADC CS5501?

Thanks,

Alyssa H.

National Instruments

[James_Creation]

Good Afternoon Alyssa,

Thank you so much for your attention and attached please find the datasheet of CSS5501.

By the way, we always get the 2 read data as 0xFF (256) and 0xFF when we use NI 8451 Write/Read VI to write 2 data to the slave SPI device.

Best regards,

James

[alyssa.h · Accepted solution]

Dear James_Creation,

Looking through the datasheet you attached for the CS5501, on page 36 there is a diagram of how they connected the CS5501 to the SPI port of the 68HC11. I would think that connecting to the NI-8451 would be similar since SPI is pretty standard. 

I have also attached some documents that may be useful to reference.

Understanding the SPI Bus with NI LabVIEW

Using the NI USB-8451 SPI Interface to Evaluate a Texas Instruments Analog to Digital Converter

The second link isn't exactly what you are doing, but some of the process, at least on the 8451 side should be similar.

Hope this helps!

Alyssa H.

National Instruments

[James_Creation]

Hi Alyssa,

Thank you very much for your attention and help,

James

[ASaifuddin]

Hi,

Do you know how to drive the MOSI line to idle low, and only go high on a high bit?

[francine.p]

The SPI protocol sets the MOSI and MISO lines to be high when idle, I couldn't find much information on how to drive them low (although you can set the base state of the clock to be low using the CPOL parameter). Why do you want the MOSI line to idle low?