Real-Time Measurement and Control

cancel
Showing results for 
Search instead for 
Did you mean: 

Using SPI for samling from multiple identical SPI measuring units such as the ADXL355

I am trying to solve a problem where i need to collect the real-time sampled signal from 16 digital MEMS accelerometers called ADXL355, through the SPI communication protocol. I am looking at the NI USB-8452 for solving this problem. My question is, can i use the chip select ports along with a decoder to gain additional chip select's.
Also, the ADXL355 requires an external clock of 10 MHz constantly during sampling and there for it would be perfect if i could set the SPI clock as constant on, if this is an option with the NI USB-8452.

0 Kudos
Message 1 of 3
(2,876 Views)

Hello,

I'm Nick, Applications Engineer at NI. I have not done a lot of SPI communication, so correct me if I'm wrong. You want to use DI channels as additional SPI ports, using a decoder (SPI-digital).

 

It is possible to do this, but it will still be recognised as a digital input line, not as an SPI line. Due to that, you will need to write some code that will integrate it with the rest of SPI lines. 

 

Regarding setting the clock rate, it is possible. Have a look at this manual, chapter 12, page 24 http://www.ni.com/pdf/manuals/371746d.pdf

 

kr,

Nick



----------------------------------------------------------------------------------------
Everything has an End, and you get to it only if you keep on
-E. Nesbit
0 Kudos
Message 2 of 3
(2,838 Views)

Hi!

 

There is a way to set multiple chip selects at once meaning that you could make more output configurations than just "1 slave at the time", please see the link below.

 

http://digital.ni.com/public.nsf/allkb/5E59F2A94E1776138625753F00042A2B

 

In this case you will need an additional device such as a decoder which you purposed that could interpret this output configurations which then could single out a slave. You could also set the DIO as Nick explained but there might be some timing issues with these as I think they might not be able to have a sufficiently fast rates. You can read more about the configuration on the link below

 

http://www.ni.com/pdf/manuals/371746d.pdf

 

Does this answer your question?

 

Best regards

Gustav, NI AE

0 Kudos
Message 3 of 3
(2,830 Views)