Sampling rate problem in multi channel data acquisition FPGA with the myRIO-1900.

[Gigalacticus]

Hi, it's a pleasure to be here and work with NI tools !!
My goal is to acquire data from all the analog accelerometers that I can connect to the myRIO-1900 so I realized the following FPGA programs. The first project was done as a test and is able to sample data from a single analogue signal at the desired 300Hz frequency. The second reads 8 accelerometers connected to analogue ports A and B, but even if with the same settings it has a much lower sampling frequency.
The accelerometers are GY-61 ADXL335 which are described in the annex with the technical data sheet. I have also attached both the projects and the two samplings in .tdms format written in the case of 1ch and 8ch. I tried to look for different guides but I can't explain this collapse in the sampling rate
Waiting for your reply, I thank you in advance for your support !!

[alamanna]

Hi,

searching the keywords related to your issue in the NI forum, I found this thread opened about a problem that seems a little different, but I hope you will find there some useful insights anyway.

Regards,

Alessia

[Gigalacticus]

Hi Alamanna

unfortunately I had also tried to double the buffer and nothing changed.

[alamanna]

Hi,

just a couple of suggestions:

• Have you tried to increase the buffer size even more?
• What happens if you try to acquire, instead of all 8 analog inputs, only 4 from the same connector (A or B)?

Please let me know!

Regards,

Alessia

[Gigalacticus · Accepted solution]

Hi Alessia after several tests I found the cause of the problem.

In fact, replacing the index array and the merge signal in the FIFO read output with Decimate 1D Array and Build Array the problems magically disappeared !!! 

[alamanna]

Hi,

I'm glad you solved it. Thank you for sharing the solution you've found!

Regards

Alessia