NI cDAQ 9171 + NI 9403 for Data Streaming

[NatineInsula]

Dear all, 

It is there any contraindication for using both the NI cDAQ 9171 Chassis with the NI 9403 DIO Module?,

The application is reading digital data from 32 ch, +-5V, 20kbps per channel, 640kbps (80kB/s) total and writing it into a TDMS stream. 

As controller I intend to use some compatible i7 barebone or a small form factor PC.

Main Specs

• NI cDAQ 9171
  • 1 slot, USB 2.0 communication, 
  • 127 samples DI FIFO.
• NI 9403
  
  • 32ch DIO, +-5V,
  • 7us | 142.9kHz clock | sampling rate.
• Controller
  • Intel Pentium i7 (3rd gen or best LabVIEW compatible),
  • 2GB RAM, 1TB HDD.

Q1: Is cDAQ enough for TDMS streaming at 320kB/s for digital serial data?

I've tested TDMS AI streaming with cRIO without trouble, but in a cDAQ i am not sure. In a cRIO 9067 i can have 4095 AI FIFO samples at the FPGA target, which in this case would be at the PC.

Q2: Is the 142.9kHz the clock rate the sampling rate?

In a previous question, some users confirmed me this for the NI 9411, which i think is also the case for the NI 9403. 

Q3: Is the sampling rate simultaneous?

I was unable to find it in the specs. 

Q4: Is the clock rate enough?

If the acquisition is indeed at 142.9kHz simultaneous, that should not have any problem for streaming 20kbps/ch simultaneous. It should sample about 7.14 clocks/sample, enough for sampling every bit. Sounds ok in theory. Am i missing something?

Q5: Should i require a cRIO instead of a cDAQ? 

If so, that would mean the NI 9403 and others DIO modules would be not compatible with the cDAQ architecture. So i am surely assuming i would not. 

Thanks for all. 

[nanocyte]

Your sales guy should be able to answer that question if someone else doesn't. I went to the example finder and selected the 9403 and the only example it selected was the SW-Timed Input example which tells me that you won't be able to sample very quickly with the 9171.

Have you thought about using an SBRIO? You'll get plenty of IO with the 9694 though you might need a bunch of resistor dividers or level shifters to bring the voltage down to 3.3V.

https://www.ni.com/en/shop/compactrio/single-board-rio/controllers-modules.html

You'd probably be fine sampling even at 1MHz for 32mbps of data

Or, you could go for a multifunction DAQ 

[dracokev]

Hey hypfco!

Are you still looking for the answers to these questions, or have you contacted your sales person like nanocyte suggested?

Let me know, and I will look into this for you!

[NatineInsula]

Sales guys in here normally dont go so deep into specific technical issues. And they want to sell services and applications to final customers too. Money rules.

[dracokev · Accepted solution]

Hey hypfco,

Sorry about the delayed response.

Here are the answers to your questions:

Q1: Is cDAQ enough for TDMS streaming at 320kB/s for digital serial data?

Yes. As I understand this question, you are asking if the USB data transfer rate is more than 320kB/s. For USB 2.0 the max transfer rate is 480 Mbit/s, so more than enough.

Q2: Is the 142.9kHz the clock rate the sampling rate?

Yes, because of the 7us rate.

Q3: Is the sampling rate simultaneous?

Yes. As this is a digital device that does not use an ADC, it is simultaneous sampling.

Q4: Is the clock rate enough?

Yes. As the sampling rate of the device is capable of 142.9kHz or 142.9kb/s and you are streaming at 20 kb/s, this is more than enough.

Q5: Should i require a cRIO instead of a cDAQ?

Nope. The system you are currently using seems fast enough for your needs.

Let me know if this helps!

[nanocyte]

Sure the bus is fast enough but I didn't see a compatible example that would allow streaming digital data. The only examples I saw were acquiring single points and for sure you couldn't run that at the full rate. If anyone's actually streamed the digital data with a cDAQ, I'd be interested i knowing that it was possible.