MATLAB: Array exceeds limits when scanning serial info

cell arraysexcelMATLABserial

I have a code that scans incoming serial information in the form of an alphanumeric tag. The program then looks through an excel sheet to find that tag, and reports the sheet and row the tag appears in:
portlist = {'COM3', 'COM4', 'COM5', 'COM6'}; % , 'COM4', 'COM5', 'COM6'
nport = length(portlist);
tags = cell(1, nport);
cleanups = cell(1, nport);
for portidx = 1 : nport
    delete(instrfind('Port', portlist{portidx})); % removes possibility for 'Port not available' error
    tags{portidx} = serial(portlist{portidx}); %initializes the port to be used
    fopen(tags{portidx}); %opens th eport
%     cleanups{portidx} = onCleanup(@() fclose(portlist{portidx}));
    cleanups{portidx} = onCleanup(@() fclose('all'));
end
addpath('C:\Users\Administrator\Dropbox (********)\******** Team Folder\Matlab\RFID chip reader\RfidChipData');
filename = 'CorrectedRFIDValues.xlsx';
[~, sheets] = xlsfinfo(filename);
in = char(zeros(1,14));
decision = fscanf(tags{portidx});   
in = decision(11:24);
rows_found = [];
sheets_found = {};
for K = 1 : length(sheets)
    this_sheet = sheets{K};
    [~, ~, raw] = xlsread(filename, this_sheet);
    [rowNum, colNum] = find( strcmp(in, raw));
    if ~isempty(rowNum)
        rows_found = [rows_found; rowNum];
        sheets_found = [sheets_found; repmat({this_sheet}, length(rowNum), 1)];
    end
end
disp(this_sheet)
disp(rowNum)
later in the code, a number of different ports are utilized for a couple other reasons. for this section, only COM3 is used. I keep getting an index out of bounds error, but I am not sure where it is coming from:
Index exceeds the number of array elements (12).
Error in Manual_auto_update2>Manual_auto_update2_OutputFcn (line 89)
in = decision(11:24);
Error in gui_mainfcn (line 264)
        feval(gui_State.gui_OutputFcn, gui_hFigure, [], gui_Handles);
Error in Manual_auto_update2 (line 42)
    gui_mainfcn(gui_State, varargin{:});
the information coming in from serial is a line, indicating a scanner number and the tag being scanned.
its looks like this:
Reader 1: 000000020F0D0%
for decision(11:24), i cut out only the tag from the entire line, as that is all I need to find in the excel sheet. I keep getting that error, however, even though I made a zeros matrix to be filled with the incoming tag. I got it to read a single time, which gave me the resulkts I was looking for. but now I have nothing. the entire code is below, which changes the color of a GUI panel based on a string comparison with the incoming serial tags, and the correct ones stored in the excel sheet. there is a number of different tags that work at different times, as well as for a number of different places.

Best Answer

I'm a bit confused by all the code you've posted. If I understood correctly the problem is with:
in = char(zeros(1,14));
decision = fscanf(tags{portidx});   
in = decision(11:24);
For a start, the first line doesn't do anything useful. Whenever you assign something to a non-indexed variable, whatever was in the variable before doesn't matter it's completely wiped out when doing the assigment:
in = something;  %doesn't matter what in was before the line. The content is completely replaced
Now, the error is Index exceeds the number of array elements (12), on the line:
in = decision(11:24);
The variable that is being indexed here is not in, it's decision. So the error tells you that the indices 11 to 24 exceed the number of elemens in |decisions. It also tells you tall number of elements is 12. So, the problem is clear, your fscanf only returned 12 characters. You'll have to figure out why. Perhaps it's a problem with your instrument. Looking at the content at what you received may give you a clue. Maybe it's an error code.
When dealing with IO, I would certainly never assume that you get what you wanted without checking that it is actually the case, so changing your code to:
[decision, receivedcount] = fscanf(tags{portidx});
if receivedcount < 24
    error('Received less data than expected. Received data was: %s', decision)
end
%now we know we've got at least 24 characters. 
%You may still want to check that the characters you receive conform to the pattern you expect. This is left as an exercise to the reader.
in = decision(11:24);
%...
Related Question