error = Index exceeds matrix dimension

Question

fremond khoo 2011-3-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2889-error-index-exceeds-matrix-dimension

good day to all matlab users and experts here,

i face some problems at work and hope to have some guidance from you all. i am working on my robotic arm project and i have develop a GUI programme to connect and run two stepper motor (motor 1 and motor 2)

i have succeeded in running motor 1 but motor 2 is not working. When i click the button CONNECT, this error came out:

??? Error using ==> serial.subsref at 137 Index exceeds matrix dimensions.

Error in ==> GUI_xyplotter>connect_m2_Callback at 129 obj2 = obj2(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('connect_m2_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

can i know what is the problem and how to solve it?..thanks a lot in advance:)

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Walter Roberson 2011-3-10

We need the code for connect_m2_Callback

fremond khoo 2011-3-10

the code for connect_m2_Callback:

% --- Executes on button press in connect_m2.

function connect_m2_Callback(hObject, eventdata, handles)

obj2 = instrfind('Type','serial','Port','COM9','Tag','');

if isempty(obj2)

obj2 = serial('COM9');

else

fclose(obj2);

obj2 = obj2(2)

end

fopen(obj2);

(my COM port is COM9)

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Answer 1

Walter Roberson 2011-3-10

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https://ww2.mathworks.cn/matlabcentral/answers/2889-error-index-exceeds-matrix-dimension#answer_4476

instrfind used with a property-value pair returns an array of objects with the desired properties. As one of the properties is the port, in order for the array to have more than one element, there would have to be more than one serial object with that exact port. That seems an unlikely situation, so I do not see why your code assumes that there will be at least two objects returned when you go ahead and access obj2(2) ?

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fremond khoo 2011-3-14

now i face another problem..first motor has no problem but the second one still got problem..when i choose COM9 from the popupmenu, this problem came:

??? Error while evaluating uicontrol Callback

??? Undefined function or variable 'obj2'.

Error in ==> GUI_xyplotter>popupmenu_com_m2_Callback at 98

a = fprintf(obj2,'%s\n','U1');

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('popupmenu_com_m2_Callback',hObject,eventdata,guidata(hObject))

??? Error while evaluating uicontrol Callback

did i type something wrong?..my coding for motor two is like this:

% --- Executes on selection change in popupmenu_br_m2.

function popupmenu_br_m2_Callback(hObject, eventdata, handles)

a = fprintf(obj2,'%s\n','U1');

b = fprintf(obj2,'%s\n','U2');

c = fprintf(obj2,'%s\n','U4');

d = fprintf(obj2,'%s\n','U6');

switch get(handles.popupmenu_br_m2,'Value')

case 1

get(a);

case 2

get(b);

case 3

get(c);

case 4

get(d);

end

% --- Executes during object creation, after setting all properties.

function popupmenu_com_m2_CreateFcn(hObject, eventdata, handles)

if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))

set(hObject,'BackgroundColor','white');

end

% --- Executes on selection change in popupmenu_br_m2.

function popupmenu_br_m2_Callback(hObject, eventdata, handles)

% --- Executes during object creation, after setting all properties.

function popupmenu_br_m2_CreateFcn(hObject, eventdata, handles)

if ispc && isequal(get(hObject,'BackgroundColor'), get(0,'defaultUicontrolBackgroundColor'))

set(hObject,'BackgroundColor','white');

end

% --- Executes on button press in connect_m2.

function connect_m2_Callback(hObject, eventdata, handles)

obj2 = find_and_open('COM9',9600);

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

fremond khoo 2011-3-15

i had successfully run both of my motor^^..thanks a lot walter^^

fremond khoo 2011-3-15

good day walter,

can i ask now that i have successfully run both of my motor using MATLAB GUI, is it possible for me to program my two-link robotic arm to draw a straight line?..

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