Problem with continuous timer object in Guide GUI

I am having trouble making a timer that runs continuously to communicate with a relay controller to check the status of one of the analog outputs. When I run the GUI I get the error:

Error while evaluating TimerFcn for timer 'timer-1' 

Object must be a figure or one of its child objects.

Here is my code for the opening of the GUI and the separate callback function for the timer:

% --- Executes just before pipeline_draft2 is made visible.
function pipeline_draft2_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject    handle to figure
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% varargin   command line arguments to pipeline_draft2 (see VARARGIN)

% Choose default command line output for pipeline_draft2
handles.output = hObject;

% Reading the gate valve to check status
echotcpip('on', 2101);
relay = tcpip('169.254.241.77', 2101);
relay.Timeout = 1;
fopen(relay);
handles.relay = relay;

% writing to relay 1
hex = ['0xAA'; '0x02'; '0xFE'; '0xA6'; '0x50'];
data = hex2dec(hex);
fwrite(relay, data)
response = fread(relay);

% Interpreting response from gate valve and setting relay buttons
if length(response) == 11
    if response(3) == 0
        set(handles.gate_valve_off,'enable','off')
    else
        set(handles.gate_valve_on,'enable','off')
    end
else
    if response(7) == 0
        set(handles.gate_valve_off,'enable','off')
    else
        set(handles.gate_valve_on,'enable','off')
    end
end

% Setting status of gate valve
if length(response) == 11
    if response(3) == 0
        set(handles.gate_valve_status, 'BackgroundColor', 'red')
    else
        set(handles.gate_valve_status, 'BackgroundColor', 'green')
    end
else
    if response(7) == 0
        set(handles.gate_valve_status, 'BackgroundColor', 'red')
    else
        set(handles.gate_valve_status, 'BackgroundColor', 'green')
    end
end

% writing to relay 1
hex = ['0xAA'; '0x03'; '0xFE'; '0x74'; '0x01'; '0x20'];
data = hex2dec(hex);
fwrite(relay, data)
solenoid_status = fread(relay);

% Setting status of solenoid
if length(solenoid_status) == 8
    if solenoid_status(7) == 0
        set(handles.solenoid_status, 'BackgroundColor', 'red')
    else
        set(handles.solenoid_status, 'BackgroundColor', 'green')
    end
else
    if solenoid_status(3) == 0
        set(handles.solenoid_status, 'BackgroundColor', 'red')
    else
        set(handles.solenoid_status, 'BackgroundColor', 'green')
    end
end

% Creating timer to update gate valve status at a rate of 20 Hz
t = timer();
t.Period = 2;
t.ExecutionMode = 'fixedRate';
t.TimerFcn = {@gate_valve_status, handles};
handles.timer = t;
start(t)

% Update handles structure
guidata(hObject, handles);

% Separate callback function for the timer object
function gate_valve_status(~, ~, handles)
    % importing info from gui
    guidata(handles.gate_valve_status, handles)
    guidata(handles.relay, handles)
    guidata(hObject, handles)
    
    % Reading the gate valve to check status
    % writing to relay 1
    hex = ['0xAA'; '0x02'; '0xFE'; '0xA6'; '0x50'];
    data = hex2dec(hex);
    fwrite(handles.relay, data)
    response = fread(handles.relay);
    
    % Setting status of gate valve
    if length(response) == 11
        if response(3) == 0
            set(handles.gate_valve_status, 'BackgroundColor', 'red')
        else
            set(handles.gate_valve_status, 'BackgroundColor', 'green')
        end
    else
        if response(7) == 0
            set(handles.gate_valve_status, 'BackgroundColor', 'red')
        else
            set(handles.gate_valve_status, 'BackgroundColor', 'green')
        end
    end
end

Any help would be appreciated.

Thanks!

Answer 1

[Image Analyst]

Look at this code:

% Separate callback function for the timer object
function gate_valve_status(~, ~, handles)
    % importing info from gui
    guidata(handles.gate_valve_status, handles)
    guidata(handles.relay, handles)
    guidata(hObject, handles)

You replaced hObject by ~ so it does not see it. But you don't even need to call guidata() at all. Just get the info from the handles structure if you need to. But I think you can probably just delete those 3 lines.

[Keir Hunter]

I am not getting an error with the timer anymore (thank you ver much) however, the GUI is not updating. The function is not in the GUI code itself, it is in a separate .m file. Will this affect anything?

[Image Analyst]

No, that's normal, at least for GUIDE. Attach both your .m and .fig files and tell me what you did.

[Keir Hunter]

Here is my .m and .fig files. I am trying to update the gate_valve_status color from red to green based on the status of a relay controller. When I open the code it works but I believe this is because I have a separate check before the timer object starts. When the timer object starts I have it call a separate function, that I have also attached, to check the relay controller. When the timer object is called the gate valve status does not updated when changed. Let me know if this helps thanks!