[SOLVED] Stepper motor with Arduino and Matlab

[GuilTy]

Hello,

I have a 28byj-48 stepper motor and the shiel uln2003. I want to program the arduino to control the stepper using Matlab.

Code:

clear all; close all; clc;
a=arduino()
configurePin(a,'D2','DigitalOutput');
configurePin(a,'D3','DigitalOutput');
configurePin(a,'D4','DigitalOutput');
configurePin(a,'D5','DigitalOutput');



pins={'D2', 'D3', 'D4', 'D5'};
steps={'1100', '0110', '0011','1001'};


steps_size=size(steps,2);                        %steps = 4

for i = 1:100

    step = steps{mod(i,steps_size)+1};      % step=1,2,3,4

    for j=1:4
        writeDigitalPin(a, pins{j}, str2double(step(j)));
    end

    %pause(0.01);

end


It works, but the speed at which the motor is turning around is very very slow. Does anyone knows how to increase the speed between Matlab and Arduino. I think that is something that has to do with the BaudRate.

Thank you,
GuilTy

[donotdespisethesnake]

I doubt that increasing the baud rate will make much difference, you will never get this to run at an adequate speed with this method.

You are using the wrong tool for the job, you should be programming the Arduino directly.

[Lovely_Santa]

It works, but the speed at which the motor is turning around is very very slow. Does anyone knows how to increase the speed between Matlab and Arduino. I think that is something that has to do with the BaudRate.

Let me explain BaudRate first: BaudRate is the speed you send data over, this is equal to your clock rate that you have on your bus. This is not equal to the amout of data you send over! (=bitrate)
When you send serial data, you send normaly 1 bit (0V or 5V => low or high => '0' or '1') every clock pulse, in this case your baudrate equals your bitrate (bitrate is number of bits you send from your PC to the arduino)
Now, we increase our detection voltages to 0, 1.5, 3, 5V => we have 4 logic levels '00', '01', '10', '11' , so in this case your baudrate isn't changing, but your bitrate has doubled.
If you can implement this in your design, this might be a sollution, but it will probably still be slow.

Your serial communication will always be your bottleneck. A way to solve this problem is to send the configuration data over to your arduino (with interrupt maybe) and then re-confugure the arduino with the received data. So even when it's not communicating, the arduino will drive the motor on it's own depending on your configuration.

So Mathlab -> Arduino sends speed & direction, or maybe number of degrees to turn (?)
Arduino driving the motor on it's own depending on configured variable speed and direction etc...

[GuilTy]

Thank you, you are right.
Now, I am using Matlab to send commands to Arduino. Arduiono has a program implemented in it and when the data is send from Matlab the motor is moved. But I can only send data from the command line in matlab, I want to build a function which sends the same data when I call it without typing the data in the command line.
Here is the code:
 function []=send_comm()
delete(instrfindall);

s=serial('COM8','BAUD', 9600); % Make sure the baud rate and COM port is
%                               % same as in Arduino IDE
fopen(s);
%
%                   
%
servalue= input('Enter the value 100 to turn ON LED & 101 to turn OFF LED :');
fprintf(s,servalue);          %This command will send entered value to Arduino
end

the "servalue" is taken with input but I have to write it in the command line. Do you know how to write a function that sends automatically the data without typing it in the command line?
If I take out "input" it doesn't work.

Best,
GuilTy

[mbless]

Change the function call to

Code: [Select]

function send_comm(servalue)and remove the input line. This programmatically inputs the value instead of requiring user intervention.

You can then call the function like

Code: [Select]

send_comm(100);
pause(1);
send_comm(101);

[GuilTy]

Thank you for your reply

Change the function call to

Code: [Select]

function send_comm(servalue)and remove the input line. This programmatically inputs the value instead of requiring user intervention.

You can then call the function like

Code: [Select]

send_comm(100);
pause(1);
send_comm(101);

It still doesn't work.

This is my arduino code:

Code: [Select]

#include <Stepper.h>

const int stepsPerRevolution = 300;  // change this to fit the number of steps per revolution
// for your motor

// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 2, 3, 4, 5);

int recValue;

void setup()
{
Serial.begin(9600);
  myStepper.setSpeed(60);
}

void loop()
{
  if(Serial.available()>0)
  {
    recValue=Serial.read();

    if  (recValue == 100)            // If use will send value 100 from MATLAB                                           then LED will turn ON
     {   Serial.begin(38400);

       myStepper.step(stepsPerRevolution);
       }
     
      }
    }

This is the Matlab code with input from the command line:

Code: [Select]


function send_comm()
delete(instrfindall);
s=serial('COM8','BAUD', 9600); % Make sure the baud rate and COM port is
%                               % same as in Arduino IDE
fopen(s);
%
%                   
%
servalue= input('Send 100 for the motor to rotate:');
fprintf(s,servalue);          %This command will send entered value to Arduino
end
This works perfectly. When I type from command line "100" the motor works perfect.

But when I write this function and only call it from the command line it doesn't do anything.

Code: [Select]

function send_comm(servalue)
delete(instrfindall);

s=serial('COM8','BAUD', 9600); % Make sure the baud rate and COM port is
%                               % same as in Arduino IDE
fopen(s);
%
%                   
%
fprintf(s,servalue);          %This command will send entered value to Arduino
end

I used HyperTerminal to monitor the transmission. Both functions send the same thing, but the motor is turnning only when I use the first function.

Regards,
GuilTy

[mbless]

Can you see if the Arduino gets the serial command? If so, what is recValue?

How are you calling the Matlab function? The only thing I can think of is if it's sending a string vs. integer. You can try

Code: [Select]

send_comm(100);or

Code: [Select]

send_comm('100');

[GuilTy]

I think that arduino gets the serial command, because when I use the first function, the one in which I have to type in the command line the value "100", it works.
And when I watched the serial connection with HperTerminal both functions have sent the same thing.


I tried using in the second function :

Code: [Select]

fprintf(s,'%d',servalue);          %This command will send entered value to Arduino
but still nothing.

And also, I tried to call the function the way you said, still doesn't work.
I don't know what else to do.

Thank you,
GuilTy

[mbless]

I think that arduino gets the serial command, because when I use the first function, the one in which I have to type in the command line the value "100", it works.
And when I watched the serial connection with HperTerminal both functions have sent the same thing.

It'd really help if you can see what the recValue is then. It should give insight as to whether there is a translation error somewhere.

[GuilTy]

It'd really help if you can see what the recValue is then. It should give insight as to whether there is a translation error somewhere.

I think you are right, but how do I see what the recValue is? Do I have to search for it in the memory of Arduino?

[FrankBuss]

Serial.begin(38400) in your loop function doesn't look good, because in Matlab you are using 9600 baud, and you need it only once in your setup function anyway. BTW, you can use 115200, too.

But Windows/Mac/Linux is not a realtime operating system. If you do a wait for 10 milliseconds, you can get anything from 10 milliseconds to 100 milliseconds if you are unlucky and e.g. Windows decides it wants to download an update in the background. Also note the USB latency, if you don't use a real built-in serial port, which can be several milliseconds as well for each communication call from Matlab. Better idea to send the whole stepper motor instructions as one block, e.g. with G code, and do all the delays and timing critical things on the Arduino side.

[GuilTy]

I solved it!
It looks like Arduino and Matlab need a short time to establish communication. Using the function in Matlab that sends the data automatically, the data didn't wait for the establishment. I had to use the command "pause" in Matlab, so the program won't send the data until the connection have been established.
This is how the code looks now.

Code: [Select]

function commanda(servalue)
delete(instrfindall);

s=serial('COM8','BAUD', 9600); % Make sure the baud rate and COM port is
                              % same as in Arduino IDE
fopen(s);

    pause(3);

fprintf(s,servalue);          %This command will send entered value to Arduino
end
Thank you all for your responses and for your interest in helping me.

GuilTy