how to control stepper motor speed via USB port

i really need some help over here..i have connected and run my stepper motor but how come i cannot control the speed of my motor?..can someone give me some hints?

below are my coding:

    function text_speed_m1_Callback(hObject, eventdata, handles)
  sliderValue = get(handles.text_speed_m1,'String');
%convert from string to number if possible, otherwise returns empty
sliderValue = str2nm(sliderValue);

%if user inputs something is not a number, or if the input is less than 0
%or greater than 100, then the slider value defaults to 0
if (isempty(sliderValue) || sliderValue < 0 || sliderValue > 256)
    set(handles.slider_speed_m1,'Value',0);
    set(handles.text_speed_m1,'String','0');
else
    set(handles.slider_speed_m1,'Value',sliderValue);
end

% --- Executes during object creation, after setting all properties.
function text_speed_m1_CreateFcn(hObject, eventdata, handles)
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))
    set(hObject,'BackgroundColor','white');
end

% --- Executes on slider movement.
function slider_speed_m1_Callback(hObject, eventdata, handles)
sliderValue = get(handles.slider_speed_m1,'Value');

%puts the slider value into the edit text component
set(handles.text_speed_m1,'String', num2str(sliderValue));
% Update handles structure
guidata(hObject, handles);

% --- Executes on button press in pushbutton_speed_m1.
function pushbutton_speed_m1_Callback(hObject, eventdata, handles)
obj1 = instrfind('Type','serial','Port','COM8','Tag','');  

if isempty(obj1)
    obj1 = serial('COM8');
else
    fclose(obj1);
    obj1 = obj1(1)
end

fopen(obj1);
sv2 = get(handles.text_speed_m1,'String');
fprintf(obj1,'%s','rs')
fprintf(obj1,int2str(get(hObject,'Value')));

please give me some hints on what i do wrong..really need help now..thanks

[Walter Roberson]

Please reformat your code to be more readable. If you go in to the editor and select the code and press the '{} Code' button then it will be reformatted.

Please also check that the code output is what you wanted. For example one of your lines shows up as "if (isempty(sliderValue) sliderValue < 0 sliderValue > 256)" which is invalid syntax. I suspect that you had or-bar there but that your or-bar was interpreted by the forum as formatting instructions.

Answer 1

[Walter Roberson]

We can't tell why you cannot control the speed of the motor. You have not described what happens when you try.

Closing and reopening the serial port each time is not advisable. If you find a serial port and it is open, then you should use it.

In your code, if obj1 is empty after the instrfind, then when you associate the serial port with obj1, you have omitted setting anything like port speed. The default probably is not what you want; even if it happens to be, other people reading your code are going to be left wondering and the defaults might change in other versions, so it is better to set port characteristics explicitly.

Answer 2

[fremond khoo]

thanks walter for the advice, i have altered my coding but the error is still there..

function text_speed_m1_Callback(hObject, eventdata, handles) 
val = str2num (get(handles.text_speed_m1,'String')); 
set(handles.slider_speed_m1,'Value',val);
%convert from string to number if possible, otherwise returns empty 
sliderValue = str2num(sliderValue); 

%if user inputs something is not a number, or if the input is less than 0 
%or greater than 100, then the slider value defaults to 0 
if (isempty(sliderValue) || sliderValue < 0 || sliderValue > 256) 
set(handles.slider_speed_m1,'Value',0); 
set(handles.text_speed_m1,'String','0'); 
else 
set(handles.slider_speed_m1,'Value',sliderValue); 
end
% --- Executes during object creation, after setting all properties. 
function text_speed_m1_CreateFcn(hObject, eventdata, handles) 
if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor')) 
set(hObject,'BackgroundColor','white'); 
end
% --- Executes on slider movement. 
function slider_speed_m1_Callback(hObject, eventdata, handles) 
val = get(handles.slider_speed_m1,'Value'); 
set(handles.text_speed_m1,'String',num2str(val));
obj1 = instrfind('Type','serial','Port','COM9','Tag','');
if isempty(obj1) 
obj1 = serial('COM8');
fopen(obj1); 
fprintf(obj1,'%s\n','S');
end 
fclose(obj1); 

%puts the slider value into the edit text component 
set(handles.text_speed_m1,'String', num2str(sliderValue));
% Update handles structure 
guidata(hObject, handles);

the error shown when i move the slider is:

??? Error using ==> serial.fopen at 72 
Port: COM8 is not available. Available ports: COM3. 
Use INSTRFIND to determine if other instrument objects 
are connected to the requested device.
Error in ==> GUI_xyplotter>slider_speed_m1_Callback at 
479 
fopen(obj1);
Error in ==> gui_mainfcn at 96 
feval(varargin{:});
Error in ==> GUI_xyplotter at 16 
gui_mainfcn(gui_State, varargin{:});
Error in ==> 
@(hObject,eventdata)GUI_xyplotter('slider_speed_m1_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

and can i ask what do you mean by "invalid syntax"?

[Walter Roberson]

Ummm, so you don't have a COM8. Is it a USB based port? If so, then you have to have it connected _before_ you start Matlab.

I am not sure why you are restricting your instrfind to the case where the Tag is the empty string? If you are not using the Tag for some purpose then it just confuses the readers. If you _are_ using the Tag for some purpose, then a comment in the code would be appreciated.

[fremond khoo]

oic..ok..i will change the tag function later^^

i have COM8 and i tried running the system but still the same error comes out..is there something wrong with my code?

[Walter Roberson]

The obvious thing to try is to close matlab and start it up again, and then without executing anything else, command,

obj1 = instrfind('Type','serial','Port','COM8')

If it cannot find COM8 then you know it isn't a problem with the rest of your code.

[fremond khoo]

i tried..i can connect to COM8..i connected and run my motor in clockwise and anticlockwise direction but when i want to change the speed of the motor by changing the slider value, the same error occured..i think there is a problem with my speed control coding but i don't know where the problem lies..

i am using stepper motor..is there a special way for stepper motor coding?

[fremond khoo]

can someone teach me how to solve this problem?..im really short of time..really hope to get some advices and help..

[Walter Roberson]

Doesn't this case correspond to you closing the existing port and opening it again? Or did you remove that code?

Answer 3

[fremond khoo]

Mr walter, my senior give me another different code to control the speed by using decimal to binary code such as this:

% --- Executes on button press in pushbutton_speed_m1.
function pushbutton_speed_m1_Callback(hObject, eventdata, handles)
sv2 = get(handles.text_speed_m1,'String');
a = dec2bin(83,8);

b = dec2bin(sv2);
c = [a b];
fwrite(obj1,c,'int16')

but when i try to execute the pushbutton to set the speed, a different error occur:

??? Error using ==> horzcat
CAT arguments dimensions are not consistent.

Error in ==> GUI_xyplotter>pushbutton_speed_m1_Callback
at 614
c = [a b];

Error in ==> gui_mainfcn at 96
        feval(varargin{:});

Error in ==> GUI_xyplotter at 16
    gui_mainfcn(gui_State, varargin{:});

Error in ==>
@(hObject,eventdata)GUI_xyplotter('pushbutton_speed_m1_Callback',hObject,eventdata,guidata(hObject))

i dun quite understand the function of dec2bin(83,8) means and what is the error of this codes..can you help me?..thanks

[Walter Roberson]

That code seems highly unlikely to work, but here is the code you would need to change:

b = dec2bin(sv2,8);

c = reshape([a;b] .', 1, []);

I would be startled fwrite(obj1,c,'int16') produces the result you are hoping for. Please re-check to see whether your senior had a bin2dec() call after c was created. Please also recheck to see if your senior converted a 10 (linefeed) or 13 (carriage return)

Your senior's code seems to be created with the idea that you send 'S' followed by a _single_ character to indicate the speed, except that the code doesn't actually do that.

Are you aware that in your original code, you do not send any value derived from the slider after the 'S'? You carefully build "val" but do not sent it to the COM port.

Please cross-check exactly what format of numbers the motor control expects. I do not see anything in your code that would restrict val to being an integer. With the range of values you are restricting to, and the code your senior provides, I wonder whether what the motor control is expecting is 'S' followed by a single byte whose decimal equivalent is the number of 1/255 of full speed -- e.g., byte value 0 for stop, byte value 128 for half speed, byte value 255 for full speed. If so then your senior's code starts to hint at some sense (but would still not be correct in the form posted.)

[fremond khoo]

im sorry walter for the late reply..i have been busying with the assembly and modifications of my robot arm..

i have checked my senior code..he does not have a bin2dec() call after c was created..his code is simply based on what i have shown above..btw i have changed the

b = dec2bin(sv2,8);

c = reshape([a;b] .', 1, []);

but still nothing happens..can you enlighten me more? and about the 'S' to control motor speed..my senior said he took from a VB source code saying the command 'S' is supposed to control the speed of the motor. Like command 'B' is the command for brake..How should i write my coding to make sure i can control my motor speed based on my senior code?..i have altered some parts of my senior code but still no luck..once again, really hope can get some help from you..

thanks a lot for your time

[Walter Roberson]

Is there a reference document that discusses the command format expected by the motor?

Answer 4

[fremond khoo]

actually i dont have any reference document that discusses the command format expected by the motor..but i have the coding of visual basic which i got from my senior..he said he refer to that code to run his motor..

the code is:

Private Sub hsbSPEED_scroll( _ 
ByVal sender As Object, ByVal e As System.EventArgs) _ 
Handles hsbSpeed.Scroll
txtSpeed.Text = CStr(hsbSpeed.Value) 
data(0) = CByte(hsbSpeed.Value)
SerialPort.Write("S") 
SerialPort.Write(data, 0, 1)
End Sub

i used the visual basic code to control my stepper motor speed and it work well..so, walter does this code means anything?

[Walter Roberson]

fwrite(obj1, [uint8('S') uint8(str2num(sv2))], '*uint8');

Or you might need 'uint8' instead of '*uint8'

Note that with this formula, the string sv2 that you get, the slider value, will be clamped to 0 if it is below 0 and will be clamped to 255 if it is above 255. You should arrange your slider to have a top value of 255.

[fremond khoo]

thanks once again walter:)..i have set my slider value to a top value of 255..and i have successfully control my motor speed..thanks once again walter..u have been a great help..cheers!!..now i can move on to the next step..thanks

[fremond khoo]

walter..i want to ask how do you know what code to write after looking at the visual basic coding which i paste above?..how do you convert them into matlab coding?..can you teach me about that?..

[Walter Roberson]

It was through experience, Fremond. Without looking it up, I could see that CByte was obviously a "convert to byte" call, and the matlab equivalent of converting to byte is uint8()

Answer 5

[fremond khoo]

oh..i understand now..so if i want to track my encoder value is also the same right?..the visual basic code is around the same with controlling the speed..

    Private Sub btnTrack_Click( _
        ByVal sender As System.Object, ByVal e As System.EventArgs) _
        Handles btnTrack.Click
        data(0) = CByte((CLng(nudTrack.Value) >> 8) And &HFF)   'High byte
        data(1) = CByte(CLng(nudTrack.Value) And &HFF)          'Low byte
        SerialPort.Write("T")
        SerialPort.Write(data, 0, 2)
    End Sub

[Walter Roberson]

It isn't obvious to me what "tracking" does for you, but according to that code, it takes as input a 16 bit integer (0 to 65535) and has no output.

tval16 = uint16(Tval);

tval16H = tval16 / 256;

tval16L = tval16 - tval16H * 256;

fwrite(s, [uint8('T') uint8(tval16H) uint8(tval16L)])

[fremond khoo]

the track function is to stop the motor when a certain value is inserted into a textbox

for example:

if i insert 3400 encoder value into the textbox then the stepper motor will receive the signal and stop exactly at 3400..

walter, can i ask lets say:

obj1 = serial('COM8');

t1 = num2str(get(handles.text_track_m1,'String'));

then i should write:

fwrite(obj1,[uint8('T') uint8(t1) uint8(tval16L)])

is it correct?

[Walter Roberson]

No, after you have obtained t1,

tval16 = uint16(t1);

tval16H = tval16 / 256;

tval16L = tval16 - tval16H * 256;

fwrite(obj1, [uint8('T'), uint8(tval16H), uint8(tval16L)])

In particular uint8(t1) is _not_ right for extracting the top 16 bits from t1: uint8(t1) when t1 is more than 255 would result in the 8 bit value 255.

[fremond khoo]

thanks walter..really thanks a lot..cheers!!

[Walter Roberson]

In the above,

t1 = num2str(get(handles.text_track_m1,'String'));

should instead be

t1 = str2num(get(handles.text_track_m1,'String'));

or one of its equivalents. str2double() is better than str2num()

Answer 6

[fremond khoo]

im sorry walter..i got another thing to ask you..i have asked my senior and he also dun knw how to program for this..I dun knw how to write the condition for this microstepping process..i need to change the microstep to 1/10 means 0.18 degree per step for my motor..can u help me?..thanks

here is the code:

Private Sub btnMstep_Click( _
        ByVal sender As System.Object, ByVal e As System.EventArgs) _
        Handles btnMstep.Click

          If cbbMicroStep.Text = "None (1 / 1)" Then
              data(0) = CByte(1)
          ElseIf cbbMicroStep.Text = "1 / 2" Then
              data(0) = CByte(2)
          ElseIf cbbMicroStep.Text = "1 / 5" Then
              data(0) = CByte(5)
          ElseIf cbbMicroStep.Text = "1 / 10" Then
              data(0) = CByte(10)
          End If
          SerialPort.Write("M")
          SerialPort.Write(data, 0, 1)
      End Sub
End Class

[Walter Roberson]

stepfactors = [1 2 5 10];

t1 = get(handles.WHATEVER, 'String');

[tf, idx] = strcmp(t1, {'None (1 / 1)', '1 / 2', '1 / 5', '1 / 10'});

if tf

stepfactor = stepfactors(idx);

fwrite(obj1, [uint8('M') uint8(stepfactor)];

else

%warn about the text not being what was expected

end

This code gets even easier if the text such as 'None (1 / 1)' are the entries for a listbox: in such a case, just get the 'Value' parameter from the handle, and as long as it is non-zero, it will be the index into the stepfactors array.

[fremond khoo]

walter..i changed into using listbox but got error:

??? Error using ==> strcmp

Too many output arguments.

Error in ==> GUI_xyplotter>pushbutton_ms_m2_Callback at

641

[tf,idx]=strcmp(M2,{'None(1/1)','1/2','1/5','1/10'});

Error in ==> gui_mainfcn at 96

feval(varargin{:});

Error in ==> GUI_xyplotter at 16

gui_mainfcn(gui_State, varargin{:});

Error in ==>

@(hObject,eventdata)GUI_xyplotter('pushbutton_ms_m2_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

what it means?..too much output argument?

[Walter Roberson]

Sorry, I misused strcmp. I should have written

tf = strcmp(t1, {'None (1 / 1)', '1 / 2', '1 / 5', '1 / 10'});

if any(tf)

stepfactor = stepfactors(idx);

fwrite(obj1, [uint8('M') uint8(stepfactor)];

else

%warn about the text not being what was expected

end

With a listbox, you would use this as the body of the callback:

stepfactors = [1 2 5 10];

idx = get(hObject,'Value');

if ~isempty(idx)

stepfactor = stepfactors(idx);

fwrite(obj1, [uint8('M') uint8(stepfactor)];

end

Answer 7

[fremond khoo]

did i write the wrong code?..

fopen(obj2);
L2 = [1 2 5 1 0];
M2=get(handles.listbox2,'String');
[tf,idx]=strcmp(M2,{'None(1/1)','1/2','1/5','1/10'});
if tf
    stepfactor=L2(idx);
    fwrite(obj1,[uint('M') uint8(L2)]);
else
fprintf('Sorry,unable to microstep');
end

[Walter Roberson]

See above, I gave you the wrong information about strcmp.

Beyond that, though, remember that the String property of a listbox is all of the configured entries for the list, not the one that is currently selected. The index of the one that is currently selected can be retrieved by getting the Value property. If you happen to want the string that corresponded to that, you can get the String property and index that by the Value; a lot of the time, though, it is better to use just the value to make it easier to change the wording of the strings (e.g., if you wanted to translate to a different language.)

[fremond khoo]

thanks walter..i have gotten the hang of it thanks to you^^..i finally be able to control the microstepping of motor..walter..can i ask u something..is it possible for me to control both motor to move to a desired position at the same time without using microcontroller?..because my supervisor asked me to do inverse kinematics on the robot arm..

is it possible for me to control only one of my motor to a desired angle through serial communication?..or is it impossible without using microcontroller?

i really would like an advice from that^^

[Walter Roberson]

I don't see any reason why you couldn't send Track commands to two different ports.

[fremond khoo]

i know why already..because i do not know the encoder value so i could not track the movement of the motor..i used the C++ code to find the encoder value but the value comes out to be a very large number..something like 2000 then to 8000..When i put the track value to be 3500 the motor will stop exactly at that number..

i have converted the 'receive encoder' code to matlab code..i try to run it..matlab shows no error but unfortunately there is no value comes out from my textbox..did i set the wrong code?

[fremond khoo]

erm..wait for a while walter..i try to edit the code again first^^

Answer 8

[fremond khoo]

Im sorry walter..in the end..i still cant change the code from C++ to matlab form..i try the same way like tracking command..but i used fscanf to get the data and want to put the value in the edit textbox..the code is around the same like track function:

   Private Sub btnAcquire_Click( _
          ByVal sender As System.Object, ByVal e As System.EventArgs) _
          Handles btnAcquire.Click
          SerialPort.Write("E")
          Dim recH As Integer = ((SerialPort.ReadByte() << 8) And &HFF00) 'High byte
          Dim recL As Integer = (SerialPort.ReadByte() And &HFF)          'Low byte
          txtEncoder.Text = CStr(recH Xor recL)                           'Combined to a 16 bits value
      End Sub

can i again ask too much of your help walter?

[Walter Roberson]

fwrite(obj1,uint8('E'));

t = fread(obj1,2,'uint8');

output = uint16(t(1)) * 256 + uint16(t(2));

A literal translation of the original code would require using char(output) instead of output as a 16 bit integer, but I suspect that the numeric form is what you want.

[fremond khoo]

can i ask what does it mean by

t=fread(obj1,2,'uint8');

what does the number '2' define?

[Walter Roberson]

The 2 means to read two items; each item will be of type uint8.

Answer 9

[fremond khoo]

thanks a lot Mr walter..i can acquire encoder value already but how to track the encoder value to stop the motor..the code is:

 function text_track_m2_Callback(hObject, eventdata, handles)
% --- Executes on button press in track_m2.
function track_m2_Callback(hObject, eventdata, handles)
obj2 = instrfind('Type','serial','Port','COM9','Tag','');  

if isempty(obj2)
    obj2 = serial('COM9');
end
fopen(obj2);
t2 = get(handles.text_track_m2,'String');
tval16 =uint16(t2);
tval16H = tval16/256;
tval16L = tval16-tval16H*256;
fwrite(obj2,[uint8('T'),uint8(tval16H),uint8(tval16L)]);

did i define something wrong?

[Walter Roberson]

You missed the str2num() or str2double() around t2

t2 = str2double(get(handles.text_track_m2,'String'));

Anything that needs to be displayed as text to the user needs to be converted to a numeric value with str2double() or str2num() or sscanf() or textscan() before it can be used for computation.

[fremond khoo]

yeah..you are right walter..i missed the str2double part..thanks a lot for your help walter^^..Walter..now that im able to track my encoder value but will i be able to change the encoder value to theta value?

i mean how can i change the encoder value to theta value (0-180 degree)?..i mean if i press a theta value in the edit textbox (text_track_m2) will the motor be able to read the theta value and stop moving?..

[Walter Roberson]

Insufficient information. No correspondence has been documented between angles and the values sent for the 'T' command.

[fremond khoo]

ic..ok..thanks a lot walter for your help..i will try to find out more info in the mean time..thanks^^..

Answer 10

[fremond khoo]

im sorry walter..i face some sort of malfunction when trying to receive the encoder value for motor 2..my coding format follows exactly like motor 1 but somehow it comes out this error:

Warning: The specified amount of data was not returned
within the Timeout period. 
??? Attempted to access t(1); index out of bounds
because numel(t)=0.

Error in ==> GUI_xyplotter>request_m2_Callback at 569
output=uint16(t(1))*256+uint16(t(2));

Error in ==> gui_mainfcn at 96
        feval(varargin{:});

Error in ==> GUI_xyplotter at 16
    gui_mainfcn(gui_State, varargin{:});

Error in ==>
@(hObject,eventdata)GUI_xyplotter('request_m2_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

motor 2 code:

fopen(obj2);
fwrite(obj2,uint8('E'));
t=fread(obj2,2,'uint8');
output=uint16(t(1))*256+uint16(t(2));
set(handles.text_request_m2,'String',output)

[Walter Roberson]

I don't see anything obviously wrong with that, but I continue to say that it is a distinct tactical error to keep opening and closing the com ports: that you should open the ports once and keep them open unless some error is encountered that forces a re-open.

[fremond khoo]

yeah..i changed the opening and closing sequence then it's working already..thanks once again walter..walter..got one part i dun understand..why is the

output = uint16(t(1))*256+uint16(t(2))

what is the meaning of this code?..i really cant understand this code..

[Walter Roberson]

t(1) is a uint8, which is an unsigned 8 bit integer. Multiplying an integer by 256 has the same effect as shifting the binary representation of the integer left by 8 bits, like (highbyte << 8) in C. Adding the 8-bit integer t(2) to the multiplied number then effectively puts t(2) in as the low-order 8 bits of the 16 bit number. The uint16() calls are there because in MATLAB when you do arithmetic operations on an 8 bit number, you get an 8 bit number out as a result but we need a 16 bit number as the result.

[fremond khoo]

thanks a lot walter..you really help me a lot this time..^^..i will try harder next time to learn more about matlab^^..thanks a lot..cheers..btw..walter..do u have any tips on learning more about matlab?..i mean do u know any links to learn other than the tutorials?..i would like to have more experience like you^^

[Walter Roberson]

There are some suggestions about learning MATLAB in a previous Question, http://www.mathworks.com/matlabcentral/answers/1148-how-to-learn-matlab

It would be fairly difficult these days to get the same kind of experience that I got -- I've been programming for 35 years, from the days when I was the only person in my class who could afford to buy a computer that could fit as many as 99 instructions...

[fremond khoo]

woa..35 years??..think i can never get the same kind of experience like you..but anyhow..i will try my best to understand more..thanks..^^

Answer 11

[fremond khoo]

Walter..i have a question for you..do you still remember the first time you help me in the connection of the motor?..

you gave me this code:

function obj=find_and_open(port,wantbaud)
obj = instrfind('Type','serial','Port',port);

if isempty(obj);
    obj = serial(port);
end

if get(obj,'BaudRate')~=wantbaud
    if strcmpi(get(obj,'Status'),'open');
        fclose(obj);
    end

      set(obj,'BaudRate',wantbaud);
  end
if ~strcmpi(get(obj,'Status'),'open');
    fopen(obj);
end

i want to ask this code should be place first before any pushbutton is callback right?..after i have define the obj, i should be able to connect to the COM by writing code like this right?

% --- Executes on button press in connect_m1.
function connect_m1_Callback(hObject, eventdata, handles)
%Create a serial port object
obj1 = find_and_open('COM8',9600);

handles.obj1=obj1
guidata(hObject,handles)

thereafter..if i want to control other buttons..can i just write like this?

     % --- Executes on button press in on_m1.
  function on_m1_Callback(hObject, eventdata, handles)
  obj1 = instrfind('Type','serial','Port','COM8','Tag','');  
fprintf(obj1,'%s\n','O');

[Walter Roberson]

For the other buttons, you should probably use find_and_open() as well.

[fremond khoo]

oh..then i will just include obj1 = find_and_open('COM',9600) at the initialization for every push button?..then fopen() is not require anymore until we close the port at the end?

[fremond khoo]

walter..way to go..i have already altered all my pushbutton to find_and_open format..^^..now no need to fopen() anymore..thanks once again

[Walter Roberson]

I suspect that if you put disp() in to appropriate places in find_and_open() that you will discover that opening only once at the beginning is enough. Still, there is always the possibility of the port getting closed somehow, so it's worth testing a while first.

[fremond khoo]

somehow..there is an error when i excuted for my 2nd motor using other com port..

??? Error while evaluating uicontrol Callback

??? Error using ==> serial.fprintf at 144

An error occurred during writing.

Error in ==> GUI_xyplotter>on_m2_Callback at 150

fprintf(obj2,'%s\n','O');

Error in ==> gui_mainfcn at 96

feval(varargin{:});

Error in ==> GUI_xyplotter at 16

gui_mainfcn(gui_State, varargin{:});

Error in ==>

@(hObject,eventdata)GUI_xyplotter('on_m2_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

why does it work for motor 1 but nor for motor 2??

i really am confuse now..@.@

[Walter Roberson]

I don't have any particular ideas. At that point, what does get(obj2) say about the object properties?

[fremond khoo]

obj2 = find_and_open('COM9',9600)

im also confuse what went wrong..what about the object properties?..do i need to change anything about that?

[Walter Roberson]

Put that fprintf() statement in a try/catch block, and when the exception occurs, display the output of get(obj2) in order to see what the internal status of the object was.

Answer 12

[fremond khoo]

before that, walter..can i arrange my code like that?..or the arrangement is totally wrong?

%find and open serial port
function obj=find_and_open(port,wantbaud)
obj = instrfind('Type','serial','Port',port);

if isempty(obj);
    obj = serial(port);
end

if get(obj,'BaudRate')~=wantbaud
    if strcmpi(get(obj,'Status'),'open');
        fclose(obj);
    end

      set(obj,'BaudRate',wantbaud);
  end

if ~strcmpi(get(obj,'Status'),'open');
    fopen(obj);
end

% --- Executes on button press in connect_m1.
function connect_m1_Callback(hObject, eventdata, handles)
%Create a serial port object
obj1 = find_and_open('COM8',9600);

% --- Executes on button press in connect_m2.
function connect_m2_Callback(hObject, eventdata, handles)
%Create a serial port object
obj2 = find_and_open('COM9',9600);

[Walter Roberson]

That looks okay.

[fremond khoo]

ok^^..then about the try/catch bracket..i never learn the function yet..izzit i arrange my code to be like this:

obj2=find_and_open('COM9',9600)

try

fprintf(obj2,'%s\n','O');

catch

end

sorry i am not very sure about the usage of try and catch..

[Walter Roberson]

obj2=find_and_open('COM9',9600)

try

fprintf(obj2,'%s\n','O');

catch

disp('It blew up real good!')

get(obj2) %no semi-colon

end

[fremond khoo]

walter..i use ur way of using try and catch function and it work..now i can control two motor at the same time^^..cheers!!..the only prob left is still the receive encoder..always comes out the same error:

??? Attempted to access t(1); index out of bounds

because numel(t)=0.

Error in ==> GUI_xyplotter>request_m2_Callback at 280

output=uint16(t(1))*256+uint16(t(2));

Error in ==> gui_mainfcn at 96

feval(varargin{:});

Error in ==> GUI_xyplotter at 16

gui_mainfcn(gui_State, varargin{:});

Error in ==>

@(hObject,eventdata)GUI_xyplotter('request_m2_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

[Walter Roberson]

Where you have the

t = fread(obj2, 2, 'uint8');

change that to

[t,count,msg] = fread(obj2, 2, 'uint8');

if count < 2

if ischar(msg)

fprintf(1,'request_m2 obj2 read returned only %d bytes, saying that %s\n', count, msg);

else

fprintf(1,'request_m2 obj2 read returned only %d bytes for an unknown reason);

end

return

end

Answer 13

[fremond khoo]

i am sorry walter..but it seems that the code is unstable..sometimes can sometimes cant..now it shows me this object properties:

It blew up real good!
    ByteOrder = littleEndian
    BytesAvailable = 26
    BytesAvailableFcn = 
    BytesAvailableFcnCount = 48
    BytesAvailableFcnMode = terminator
    BytesToOutput = 0
    ErrorFcn = 
    InputBufferSize = 512
    Name = Serial-COM9
    ObjectVisibility = on
    OutputBufferSize = 512
    OutputEmptyFcn = 
    RecordDetail = compact
    RecordMode = overwrite
    RecordName = record.txt
    RecordStatus = off
    Status = open
    Tag = 
    Timeout = 10
    TimerFcn = 
    TimerPeriod = 1
    TransferStatus = idle
    Type = serial
    UserData = []
    ValuesReceived = 0
    ValuesSent = 35

      SERIAL specific properties:
      BaudRate = 9600
      BreakInterruptFcn = 
      DataBits = 8
      DataTerminalReady = off
      FlowControl = none
      Parity = none
      PinStatus = [1x1 struct]
      PinStatusFcn = 
      Port = COM9
      ReadAsyncMode = continuous
      RequestToSend = off
      StopBits = 1
      Terminator = LF

[Walter Roberson]

Change the find_and_open function as follows and try again:

function obj=ODF_plot(port,wantbaud)

needed_open = true;

obj = instrfind('Type','serial','Port',port);

if isempty(obj);

fprintf(1,'find_and_open: note that instrfind did not find port %s\n', port);

obj = serial(port);

end

curspeed = get(obj,'BaudRate');

if curspeed ~= wantbaud

if strcmpi(get(obj,'Status'),'open');

fclose(obj);

needed_open = false;

fprintf(1,'find_and_open: note that port %s was already open but had the wrong speed, %d\n', port, curspeed)

end

set(obj,'BaudRate',wantbaud);

end

curmode = get(obj,'BytesAvailabelFcnMode');

if ~strcmpi(curmode, 'byte')

if strcmpi(get(obj,'Status'),'open');

fclose(obj);

needed_open = false;

fprintf(1,'find_and_open: note that port %s was already open but had the wrong mode, %s\n', port, curmode)

end

set(obj,'BytesAvailabelFcnMode', 'byte');

end

if ~strcmpi(get(obj,'Status'),'open');

fopen(obj);

if needed_open

fprintf(1,'find_and_open: needed to open port %s\n', port);

end

end

Answer 14

[fremond khoo]

Walter..it come out this error:

??? Undefined function or method 'find_and_open' for
input arguments of type 'char'.

Error in ==> GUI_xyplotter>on_m1_Callback at 106
obj1 = find_and_open('COM8',9600);

Error in ==> gui_mainfcn at 96
        feval(varargin{:});

Error in ==> GUI_xyplotter at 16
    gui_mainfcn(gui_State, varargin{:});

Error in ==>
@(hObject,eventdata)GUI_xyplotter('on_m1_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

it seems it cannot read the find_and_open function when i executed the buttons..

[Walter Roberson]

Sorry, where I wrote ODF_plot change that to find_and_open .

Answer 15

[fremond khoo]

yeah..i changed the code into find_and_open and try it out..but the error is something i never seen before..

??? Error using ==> serial.get at 71
There is no 'BytesAvailabelFcnMode' property for serial
port objects.

Error in ==> GUI_xyplotter>find_and_open at 63
curmode = get(obj,'BytesAvailabelFcnMode');

Error in ==> GUI_xyplotter>connect_m1_Callback at 84
obj1 = find_and_open('COM8',9600);

Error in ==> gui_mainfcn at 96
        feval(varargin{:});

Error in ==> GUI_xyplotter at 16
    gui_mainfcn(gui_State, varargin{:});

Error in ==>
@(hObject,eventdata)GUI_xyplotter('connect_m1_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

[Walter Roberson]

Typo, should have been BytesAvailableFcnMode

[fremond khoo]

yup..that's the prob^^..changed already..now is functioning..but for the receive encoder part..it still came out the same error eventhough i din open and close my port the whole time..

same error..

??? Attempted to access t(1); index out of bounds

because numel(t)=0.

Error in ==> GUI_xyplotter>request_m1_Callback at 249

output=uint16(t(1))*256 + uint16(t(2));

Error in ==> gui_mainfcn at 96

feval(varargin{:});

Error in ==> GUI_xyplotter at 16

gui_mainfcn(gui_State, varargin{:});

Error in ==>

@(hObject,eventdata)GUI_xyplotter('request_m1_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

is it because i use the function t(1) for both COM until COM9 cannot read t(1) function because it is open in COM8?

[Walter Roberson]

No, t is a local variable, not a function, and the value in one routine would not affect the value in another.

Did you not make the parallel change to the one I indicated earlier?

=== begin quote ===

Where you have the

t = fread(obj2, 2, 'uint8');

change that to

[t,count,msg] = fread(obj2, 2, 'uint8');

if count < 2

if ischar(msg)

fprintf(1,'request_m2 obj2 read returned only %d bytes, saying that %s\n', count, msg);

else

fprintf(1,'request_m2 obj2 read returned only %d bytes for an unknown reason);

end

return

end

=== end quote ===

Do the same thing for request_m1_Callback except changing 2 to 1 for the object number and warning messages.

[fremond khoo]

im sorry walter..i did not change to parallel before that..now that i have changed..it has no error..but it state it receive 0 bytes from my motor..

the statement:

request_m1 obj1 read returned only 0 bytes, saying that The specified amount of data was not returned within the Timeout period.

[fremond khoo]

it's working walter^^..try again and success!!..deepest gratitude towards walter~~..thanks

Answer 16

[keycamel villegas]

hi fremond khoo..did you used a motor driver for your stepper motor?and may i know what are the connections?thank you!!.. im a newbie in matlab..and my thesis project involves the movement of a bipolar stepper motor. :)

[fremond khoo]

im sorry keycamel villegas for the late reply..yup..i use SD02B motor driver(u can search from www.cytron.com)..the connection is fairly easy..just go to cytron and u will know everything^^..cheers..they even provide a manual for you..just go ahead and try it out..my project is about unipolar stepper motor^^

Answer 17

[keycamel villegas]

my project involves a bipolar stepper motor and im using L298 motor driver..would it be possible that your code above can be used in our project?

[fremond khoo]

you can try them out..u are using serial port or parallel?

[keycamel villegas]

our professor said that our connection would be:

RS232 to serial to parallel converter(using 4 bit shift register) to l298 motor driver connected to bipolar stepper motor,,

would that be possible?or can you suggest other connection for our bipolar stepper motor because i have difficulty analyzing the connections of this components,,

by the way THANK YOU for your reply :)

Answer 18

[keycamel villegas]

our professor said that our connection would be:

RS232 to serial to parallel converter(using 4 bit shift register) to l298 motor driver connected to bipolar stepper motor,,

would that be possible?or can you suggest other connection for our bipolar stepper motor because i have difficulty analyzing the connections of this components,,

by the way THANK YOU for your reply :)

[fremond khoo]

RS232 is your stepper motor model??..for my project..i use RS440-442 and RS440-420 unipolar stepper motor and connect them to two driver motor and from the driver motor connect them to laptop using UART converter (UC00A)..you are welcome..people help me then im glad i can help others back^^

[keycamel villegas]

RS232 is a usb to serial connector then it will be connected to a serial to parallel converter(using 4 bit shift register) and it will be connected to a L298 motor driver, connected to a bipolar stepper motor.

sorry for many questions im asking...it just that im a newbie in matlab..thanks for the effort answering my problems

Our goal is: Matlab controlling stepper motor

[Walter Roberson]

Please take this to a new Question, "keycamel": this one is already long enough to make it difficult to find useful information in.

[fremond khoo]

walter^^..today i finish my final presentation and my evaluator was very impressed with my project..at here i wish to say thanks again to all of your help from the bottom of my heart..^^..thanks again

[keycamel villegas]

can i asked you a question? how uart of a microcontroller communicate with the uart of matlab?.thank you

[Walter Roberson]

The program running on the microcontroller uses system-specific methods to cause the microcontroller's UART to send the bytes out.

Please start a new question for these kinds of topics; this question is very long and difficult to follow.