Generating square wave using an embeded matlab function

Hi,

I intend to generate a square wave which is applied on a DSP.

I have written these codes and put them in an embeded Matlab function.

function y = fcn(u)

%#eml

t=0:0.001:1

h = sign(sin(125600*t+u));

y= (h+1)/2

where, u is a constant value of 0.582 which is used for shifting the square wave.

The problem is at the out put in the simulation, instead of getting a square wave, I see only two straight lines of y=o and y=1.

Please let me know where is the problem that I can not get the square wave?

Note that the frequency of square wave must be 20 kHz. Therefore, I adjust the sampling time as 1e-7 s. And also its amplitude is between 0 and 1 In addition, due to this signal must be transferred to a DSP board, in the "solver option" I chose the type: " Fixed-step" and for the Solver: "Discrete (no continues state)".

Thanks a lot.

[Azzi Abdelmalek]

Sayedfoad, I suppose that you are accepting answers randomly.

Answer 1

[Walter Roberson]

Your function is fine. You are not zoomed in enough to see the wave transitions.

[Seyedfoad Taghizadeh]

Thanks a lot for your reply, Actually, when I zoom in I can not see the output. Even when I convert this system using a compiler on a DSP board, it is compiled completely, but I can not see the waveform on Oscilloscope as well.

Please let me know if there is a solution.

Answer 2

[Azzi Abdelmalek]

Seyedfoad, You can't define the time inside the Embedded function, you can notice that your output y is not a scalar, but a vector with length equal to numel(0:0.001:1). The two lines you are seeing, are the 51 output of your embedded function that are equal to 1 for some of them and 0 for the others, you can check this by using a [to workspace] block.

But the question is, why not to just use a pulse generator block?

You can use an embedded function with an input signal t coming from a clock block. and the code is the same as yours without the vector time

function y = fcn(t)
u=0.582;
h = sign(sin(125600*t+u));
y= (h+1)/2;

[Seyedfoad Taghizadeh]

Highly appreciated for your useful answer. You opened my eyes. I tried it on simulation and it worked. As I mentioned, I must transfer this system on a DSP board and the DSP board accepts only discrete time blocks. I do not know the "clk" can be accepted by DSP or no. I have to test it.

Thanks again for your useful answer.

Regards Foad

[Seyedfoad Taghizadeh]

Dear Mr. Azzi Abdelmalek

I tried the "clock" block in the simulation and could get the square wave signal as an output. In the simulation, it is fine. But when I try to transfer it on DSP the compiler reports this error:

---------

Block 'Final2/Clock' uses continuous time, which is not supported with the current configuration. Consider selecting the support 'continuous time' option on the Configuration Parameters > Real-Time Workshop > Interface page.

---------

Then I followed the error and I went to Configuration Parameters > Real-Time Workshop > Interface page and ticked the "continuous time". But after doing this, when I tried again, I received this new error:

--------------

The Embedded-C code format does not support continuous sample time blocks.

--------------

Please let me know if you have any idea. Certainly, it would be very effective to solve my problem.

Regards

Foad

[Azzi Abdelmalek]

I suppose you are working with a fixed-step, Try a digital clock block instead of a clock

[Seyedfoad Taghizadeh]

Thanks alot, I used the block and it worked.

Regards Foad

[huynh quyen]

dear Foad, I want to generate 40khz pulse wave on raspberry pi , I used your block as the figure following but not accurately, simulation is display precisely but when I measure on ocsiloscope is wrong display. Please, help me.