How to make the x-axis of a graph restart from 0 again when pushing a start button after have stopped the plotting process?

I'm working in a GUI which shows current and speed vs time of a DC Motor.

When pushing the start button from the beginning both graphs start from time 0.

The problem that I have is that when pushing the stop buttton to stop the process and when I'm using the GUI to collect these signals to plot them, so I would like you to help me to make the ESP32 time set to zero when pushing the start button again to plot current and speed correctly.

I'm attaching the code as well as the video that shows the GUI working.

            % Button pushed function: StartButton
            function StartButtonPushed(app, event)
            
            clear app.current app.speed app.time
            app.current = [];
            app.speed = [];
            app.time = [];
            
            cla(app.UIAxes);
            cla(app.UIAxes2);

            set(app.StartButton,'Enable','off')
            set(app.SaveButton,'Enable','off')
            set(app.LoadButton,'Enable','off')

            if strcmpi(app.StartButton.Enable,'off')
                MQTTSignal = mqttclient('tcp://broker.hivemq.com','Port',1883);  
                Topic = "ESP32/status";
                Message = "1";
                app.SystemOffLamp.Color = 'g';
                app.SystemOffLabel.Text = 'System On';
                write(MQTTSignal,Topic,Message);
            end

            % Connection to MQTT
            MQTTSignal = mqttclient('tcp://broker.hivemq.com','Port',1883);
            Topic = "ESP32/data";
            Data = subscribe(MQTTSignal,Topic);
            
            
            pause(3);

            while strcmpi(app.StartButton.Enable,'off')  

                dataTT = read(MQTTSignal);
                str = (dataTT.Data);
                str = strrep(str, '{', ''); % remove opening bracket
                str = strrep(str, '}', ''); % remove closing bracket
                str = split(str,",");
                app.current_temp = str2double(str(:,1));
                app.speed_temp = str2double(str(:,2));
                app.time_temp = str2double(str(:,3));
                app.current = [app.current;app.current_temp];
                app.speed = [app.speed;app.speed_temp];
                app.time = [app.time;app.time_temp];
         
                plot(app.UIAxes,app.time,app.current);
                
                plot(app.UIAxes2,app.time,app.speed);
  
                drawnow
                pause(3)
  
            end
           
            % Button pushed function: StopButton
            function StopButtonPushed(app, event)
            

            if strcmpi(app.StopButton.Enable,'on')
                MQTTSignal = mqttclient('tcp://broker.hivemq.com','Port',1883); 
                Topic = "ESP32/status";
                Message = "0";
                app.SystemOffLamp.Color = 'r';
                app.SystemOffLabel.Text = 'System Off';
                write(MQTTSignal,Topic,Message);
               
            end
            set(app.StartButton,'Enable','on');
            set(app.SaveButton,'Enable','on');
            
            

GUI DC-Motor Video

[Ayush]

Hi @Luis Ricardo Rivera Goitia,

To set the ESP32 time to zero when pushing the start button again, you can use the following steps:

1. Add a variable to store the start time when the start button is pressed for the first time.
2. When the start button is pressed, check if the start time variable is null. If it is null, set the start time to the current time.
3. If the start time variable is not null, subtract it from the current time to get the elapsed time. Use this elapsed time as the x-axis value for the current and speed graphs.
4. When the stop button is pressed, set the start time variable to null.

[Luis Ricardo Rivera Goitia]

Great! Thank you @Ayush

Answer 1

[Ayush]

Hi @Luis Ricardo Rivera Goitia,

To set the ESP32 time to zero when pushing the start button again, you can use the following steps:

1. Add a variable to store the start time when the start button is pressed for the first time.
2. When the start button is pressed, check if the start time variable is null. If it is null, set the start time to the current time.
3. If the start time variable is not null, subtract it from the current time to get the elapsed time. Use this elapsed time as the x-axis value for the current and speed graphs.
4. When the stop button is pressed, set the start time variable to null.