Question

I want to make a GUI have a slider, this slider’s value will be used to transmit serial data to PIC microcontroller.

The output value of the slider must be a character or string.

1. How can I define enter code here variable in matlab gui?

2. How can I know the type of output value of slider ? (int, char, …)

code:

s=serial('COM7');
slider_value = get(handles.slider3, 'value');
fopen(s);
fprintf(s,'%s',slider_value);
fclose(s)

Answer 1

Useful information: http://www.mathworks.se/help/techdoc/ref/uicontrol_props.html.

The type of the Value property is the scalar value it currently has. This value will between Min and Max which defaults to 0 and 1, respectively. Did you set these to other values? The scalar value will likely be in double representation so you need to convert to a string:

Put this in your init-section (a slider that goes from 0 to 100):

set(handles.slider3, 'Min', 0); %set min to 0 (default)
set(handles.slider3, 'Max', 100); %set min to 100 (default)
set(handles.slider3, 'SliderStep', [1 10]);

And this in your callback routine:

s = serial('COM7');
slider_value = get(handles.slider3, 'Value');
fopen(s);
fprintf(s, '%u', uint32(slider_value));
fclose(s)

The above is just an example. You should set Min, Max, and SliderStep to what you want. Find the relevant sections in the UIcontrol properties documentation that I link to in the beginning. You should also note that I send the data as an unsigned 32-bit value (not the recast).