increrasing maximum rate of reading quadrature encoder on myRIO

[farshid_asadi]

Hi

As stated in the specs, max rate for reading quadrature encoders with myRIO default functions is 100kHZ.

Since the FPGA runs at 40MHz, so I think there is a good probability that we can increase the rate at which we can read quadrature encoders (I need something about 4 MHz).

Since I am new to myRIO, so I decided to consult about this before going further.

If I modify FPGA personality and delete unneeded features (and probably write my own quadrature encoder reading algorithm), is it possible to increase the maximum rate that I can read quad encoder?
If yes, how much this increase will be? 40MHz (since FPGA it acts as a gate)?

Best

Farshid

[Chuan19]

Hi farshid, you can use the FPGA inputs to receive tha signals and decode them for the information you need. The KB below might yield helpful.

NI 9411 Quadrature Encoder LabVIEW FPGA Example Code
https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000kEpeSAE&l=en-US

[farshid_asadi]

Hi

Thanks for your response.

I had seen these code before. But my question is how fast I can get if I modify the FPGA and get rid of other things that I do not need.

I also need to keep three pwm channel.

Best

Farshid

[Chuan19]

Checking at the manual, it seems that the data speed is restricted due to the bus switch speed. 

myRIO-1900 User Guide and Specifications
http://www.ni.com/pdf/manuals/376047c.pdf#page=11

[farshid_asadi]

Since for bus switch no rate limit explicitly stated and since default SPI interface works up to 4MHz, so I think we can assume that digital inputs can work at 4MHz. Therefor I think we can conclude that we can increase quadrature encoder max reading rate.