Matlab GUI: How to use fprintf function by writing a value between two chars

Main objective:

I want to write a GUI MATLAB code that will allow me to send commands to an instrument and receive information from instrument.

Introduction:

First of all, I wish to thank Roger Yeh for sharing his serial_GUI matlab code. I took his simple application and tried to implement for my purposes. I have a specific command set that I can use to communicate with the instrument. For example when setting fine values I need to use the following command: SF z0 40<cr> , where z0 is a variable; 40 is the set value and<cr> is carriage return.

Problem description:

When I wish to define my command within fprinf I don't seem to get the string/value/string format. Here is the code I use for sending information to the instrument:

z0valf=str2double(get(handles.z0f,'String'));
  %fprintf(handles.serConn,'SF z0 %d<cr>\n',z0valf); %serConn - holds information about serial port
  currList = get(handles.history_box, 'String');
  set(handles.history_box, 'String', ...[currList ; ['Sent @ ' datestr(now) ': SF z0 ' z0valf '<cr>']]);
  set(handles.history_box, 'Value', length(currList) + 1 );

Getting information from the instrument:

try 
    RxText = fscanf(handles.serConn)
    currList = get(handles.history_box, 'String');
    if length(RxText) < 1
        RxText = 'Timeout @ ';
        set(handles.history_box, 'String', ...
            [currList ; [RxText datestr(now)] ]);
    else
        set(handles.history_box, 'String', ...
            [currList ; ['Received @ ' datestr(now) ': ' RxText ] ]);
    end
    set(handles.history_box, 'Value', length(currList) + 1 );
catch e
  disp(e)
end

Output in the history_box:

    Sent @ 05-Mar-2018 19:25:19: SF z0 □<cr>
    Received @ 05-Mar-2018 19:25:29: SF z0 5<cr>

The □ should be 5, how could I change this?

What I also tried is to input everything in a editable box and just use that within the fprintf function.

My second problem is that I seem to experience a lag when I read data from the serial COM port. The reason I know this is that when let's say I set the fine value writing in the full command line within a textbox and send that to the instrument. When I try to read the data using the get fine value( GF z0<sp>) it does not give me the same information as when I write it in Putty.

Can anyone give any help on this? Thank you in advance. In case I did not give enough information/details please let me know.

Answer 1

[Walter Roberson]

   set(handles.history_box, 'String', ...[currList ; ['Sent @ ' datestr(now) ': SF z0 ' str2num(z0valf) '<cr>']]);

[Örs Istok]

Thank you for your answer, however it did not seem to work. It gave me this error: 'Error using str2num (line 31) Requires character vector or array input.'

[Walter Roberson]

Sorry I keep confusing str2num() and num2str()

[Stephen23]

str2double(z0valf)

Answer 2

[Örs Istok]

Meanwhile I also figured out how to solve the lag between the instrument and computer. If any of you is interested, then I can shortly summarise it.