how to control stepper motor speed via USB port
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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
1 Comment
Walter Roberson
on 27 Mar 2011
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.
Accepted Answer
Walter Roberson
on 27 Mar 2011
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.
0 Comments
More Answers (17)
fremond khoo
on 27 Mar 2011
6 Comments
Walter Roberson
on 28 Mar 2011
Doesn't this case correspond to you closing the existing port and opening it again? Or did you remove that code?
fremond khoo
on 29 Mar 2011
3 Comments
Walter Roberson
on 31 Mar 2011
Is there a reference document that discusses the command format expected by the motor?
fremond khoo
on 31 Mar 2011
4 Comments
Walter Roberson
on 1 Apr 2011
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()
fremond khoo
on 2 Apr 2011
5 Comments
Walter Roberson
on 7 Apr 2011
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()
fremond khoo
on 6 Apr 2011
3 Comments
Walter Roberson
on 7 Apr 2011
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
fremond khoo
on 7 Apr 2011
4 Comments
Walter Roberson
on 8 Apr 2011
Insufficient information. No correspondence has been documented between angles and the values sent for the 'T' command.
fremond khoo
on 8 Apr 2011
6 Comments
Walter Roberson
on 10 Apr 2011
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
on 11 Apr 2011
8 Comments
Walter Roberson
on 11 Apr 2011
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.
fremond khoo
on 12 Apr 2011
5 Comments
Walter Roberson
on 12 Apr 2011
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
fremond khoo
on 12 Apr 2011
1 Comment
Walter Roberson
on 12 Apr 2011
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
keycamel villegas
on 16 Apr 2011
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. :)
keycamel villegas
on 19 Apr 2011
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?
2 Comments
keycamel villegas
on 19 Apr 2011
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 :)
keycamel villegas
on 19 Apr 2011
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 :)
6 Comments
keycamel villegas
on 6 May 2011
can i asked you a question? how uart of a microcontroller communicate with the uart of matlab?.thank you
Walter Roberson
on 6 May 2011
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.
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