How to interface touch screen with simulink to determine the position of a moving ball on a plate

Hi, Im attempting to use a 4 wire resistive touch screen to determine the position of a ball on a given plate. The idea is that the error from the reference point will be calculated and then using a state space regulator servo motors will adjust the plate to return the ball to its reference position. I'm having trouble with the touch screen. I am trying to run it through an Arduino mega 2560. Essentially voltage is applied to X+ while X- and Y- are tied to ground and voltage read from Y+ and vice versa. This isn't working out too well for me. Is there a better way of doing this in particular to have it working in simulink. I have completed a lot of searches but can only find references to touch screens and Arduino boards but nothing discussing how it was completed. Any help would be very more appreciated. Even been pointed in the right direction would be great. Thanks peter

[Jordan Ross]

Can you please elaborate what is wrong with the touch screen? I.e. are you not seeing the data in Simulink? Also can yo explain how you have the touch screen connected to your Arduino?

[peter bennett]

Hi Jordon, I have written a .m file which displays the required information perfectly. I dont know how best to go about importing this data into simulink. I have tried to import as a variable and using the likes of sigdata and the from workspace function. None of these seem to be able to import the information i require. Bearing in mind that the info is stored in a 2x1 matrix which is been continually updated. Essentially how can i create a simulink block from a .m file to run continuously for an analog input from an arduino board

[Jordan Ross]

Hello Peter,

You are correct, those blocks will only read the the workspace values once at the simulation start. What you can do is use a MATLAB Function block. In that function block you can have the following code:

function y = fcn
    coder.extrinsic('evalin');
    y = zeros(2,1);
    y = evalin('base','x');
end

This assumes that the value you want to read is a "2x1" and is stored in a variable "x". You can also configure the MATLAB Function block to have a sample time that meets your design specification.

As an example I tested using this simple model:

Then, from the MATLAB Command Window I just manually changed the value of "x".

[peter bennett]

Thanks a million for your help. I'll try that out this evening and let you know how I get on. Here's hoping it works. Thanks again

[peter bennett]

Hi Jordon, Sorry to trouble you again and thanks so much for all the help. So I did as you suggested and yeah I got a result into Simulink. The only thing is that it only takes the initial position of the ball. I have the code attached below maybe you can spot my error. Any help would be really appreciated.

    % 
clc
clear
a = arduino('com5','mega2560');
for i = 1:500
configurePin(a,'A1','AnalogInput'); 
configurePin(a,'A3','AnalogInput'); 
configurePin(a,'A0','Digitaloutput');
writeDigitalPin(a,'A0',0);
configurePin(a,'A2','Digitaloutput');
writeDigitalPin(a,'A2',1);
x =readVoltage(a,'A1')/1;
configurePin(a,'A0','AnalogInput'); 
configurePin(a,'A2','AnalogInput'); 
configurePin(a,'A1','Digitaloutput');
writeDigitalPin(a,'A1',0);
configurePin(a,'A3','Digitaloutput');
writeDigitalPin(a,'A3',1);
y =readVoltage(a,'A0')/1; 
Position =[x y]
%
%
% separate block 
function y = fcn
coder.extrinsic('evalin');
y=zeros(2,1);
y=evalin('base','Position');

end

[Cheung Ka Sin]

Hello Peter,

Have you got any solution about your problem?

It's because I am facing the same question about the MATLAB function input to the Simulink.

I am already write the function in MATLAB for getting the position of touch screen position.

But it cannot input to the Simulink/ run MATLAB and Simulink at the same time.

[Jorge Bravo]

Could you solve the problem? I'm doing the same project and I can not export the position to the workspace, to send it to simulink

[peter bennett]

Hi so in short no I never managed to resolve the issue with Matlab. After multiple attempts, I switched to Labview. The system was a lot slower but did the job. Heres a video of the final project https://www.youtube.com/watch?v=BBnsqx9affk

[Jorge Bravo]

it is a requirement to use matlab for the project, and your command line is the only thing that has worked for me ... thanks for the help, I will continue investigating

[William Jara Loaiza]

Hello everyone, I share my little experience in this same project since like all of us here I have researched a lot of this.

I have not yet been able to solve Peter's problem because as mentioned, with MatLab it is very complicated to communicate the touch screen and send the data to simulink in real time. For all this I found a way in which the programming similar to the one mentioned in matlab is loaded in arduino, then arduino sends the values of the position through the serial port where now we can read them in real time from simulink.

Here I share a link that explains a bit how to do the serial communication that I am referring to.

https://wechoosethemoon.es/2011/07/21/arduino-matlab-simulink-controlador-pid/

[Ahmet Ünser]

Hello everyone,

I'm working on the same project "Ball on Plate" right now. Does anyone have a solution for this problem?

I want to see the output of the touchscreen via simulink.

Would be grateful, if anyone could help me further.

Thank you in advance !