Sample rate in Analog Input/Output blocks in Simulink

I am preparing a class assignment with NI myDAQ where the sample rate should be a variable to be defined by the students.

Sample rate should be a variable in the workspace so students can change it according to results from previous computations on the system itself.

If I try to insert a variable, defined in the workspace as a positive number, I get error. Is there a workarounf for it?

[Manikanta Aditya]

What is the error you encountered?

[Anna]

If I try to enter N as Sample rate in the block parameters (N exists in the workspace and N=50) I get the message that: "Sample rate must be specified as a positive real number".

Answer 1

[Avni Agrawal]

Hi Anne,

I understand that you are trying to use NI myDAQ with Simulink, setting the sample rate as a variable from the MATLAB workspace can sometimes cause issues. Here's how you can work around this:

1. Define the Variable Before running your model, ensure the variable is defined in the workspace. For example:

N = 50; % Sample rate, can be changed by students

2. Use a Constant Block: Instead of directly entering the variable into block parameters, use a Constant block:

• Drag a Constant block into your model.
• Set its value to `N`.
• Connect it to the block where the sample rate is needed.

3. MATLAB Function Block: If you need more flexibility, use a MATLAB Function block:

• Add a MATLAB Function block to your model.
• Inside the function, use `N` to set the sample rate.

function y = setSampleRate(N)

y = N; % Use N as the sample rate

end

4. Parameterize the Model: Ensure your model is set up to use workspace variables:

• Go to `Simulation` > `Model Configuration Parameters`.
• Check the `Data Import/Export` settings to allow workspace variables.

By following these steps, you can successfully use a workspace variable as the sample rate in your Simulink model with NI myDAQ.

I hope this helps!