How can i multiplex sensors using the FPGA

[milo_unlimited]

Hi,

Im using a Robotics starter kit, and the FPGA chip is too small for the code i try to put in there, so i am trying to make several functions smaller.

I am using 8 identical sensors and i have a subVI which returns the distance measured and wheather the sensor timed out or not, but i dont know how to re-use the same function for every sensor.

Can somebody help me?

[srm@viewpointusa.com]

not enough information to help you yet.  what is the code within the measurement function?

if it has memory like a shift register, you either need to code it as an array or use memory to implement a piece of code that be iterated on within a loop.

[milo_unlimited]

Thats a good point. I added the entire code, so maybe you can take a look?

I cant seem to put the IOadresses into an array... Maybe it is possible and maybe its the solution to my problem 🙂

tnx in advance

[milo_unlimited]

Maybe this will help 🙂

Total subVI:

Pieces of the subVI(enlarged):

[milo_unlimited]

I tried to make an array of the 8 IOpins, but when I try to make a for-loop to use them all i get multiple error messages:

"Possibility of Dynamic Refnum not supported for current target"

When I make it a fixed-array I get the same error message

[CMal]

The best solution would be to create a separate while loop for each of the sensors (see attached image).  I tried this with the sensor loop, and it compiled fine for an sbRIO-9631.

You should avoid calling the Measure Distance sub VI sequentially in a For Loop because the VI takes up to ~20 ms to run.  This is how long it takes for the ultrasonic sensor to receive a response pulse at maximum range.  Running the VI in an 8-iteration For Loop would result in 1/8th the sensor frequency for each sensor.  Using parallel loops will avoid this problem.

Chris M

[srm@viewpointusa.com]

are all of these events synchronized?  as in they are all initiated at the same time and should complete within the same timeout?

How often is the sequence repeated?

I understand that you are trying to fit onto the FPGA and are looking to reduce the code footprint by multiplexing the code.  I also assume that you need the digital input response to be as fast as possible to provide the best resolution.

[milo_unlimited]

For some reason I can only fit 2 sensors into my FPGA module...

I need a minimum of 4 sensors...

[CMal]

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@milo_unlimited wrote:

For some reason I can only fit 2 sensors into my FPGA module...

I need a minimum of 4 sensors...

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Have you made any other modifications to the FPGA code, other than adding extra sensor loops?  Can you attach the modified example you are trying to compile?

Chris M

[milo_unlimited]

The project contains 2x  dualmotordrive units, 8 simple digital sensor connectors, SPI-communication, a custom serial comunication for a linescan module and hopefully 4 ultrasonic sensors

Attached the entire project(.7z file in a .zip file because 7z is not supported on this forum). Hope somebody can help :-S