how to use while loop

I am using 2 variables for getting(Receiving) data from serial port. I want to use while loop to operate these two variables. I am using following two variables : 1. Rcvd_1 & 2. Rcvd_2

I want to create a code in such a way that first i will check that Rcvd_1 is null and if so then i will start filling it, and as soon as it fills data storage will start in Rcvd_2.

While Rcvd_2 is filling i want to clear variable Rcvd_1.

So please suggest me what type of looping condition should be neede to do so.

Thanks in advance

Answer 1

[Walter Roberson]

chunk_size = 8192;    %or as appropriate

while true
   this_byte = fread(s, 1);

     %check that Rcvd_1 is null and if so then i will start filling it
     if ~exist('Rcvd_1', 'var')
       Rcvd_1 = zeros(1, chunk_size, 'uint8');
       idx1 = 0;
     end

     %fills data storage 
     if idx1 < chuck_size
       idx1 = idx1 + 1;
       Rcvd_1(idx1) = this_byte;

     %as it fills data storage will start in Rcvd_2.
     else
       %check that Rcvd_2 is null and if so then i will start filling it
       if ~exist('Rcvd_2', 'var')
         Rcvd_2 = zeros(1, chunk_size, 'uint8');
         idx2 = 0;
       end
       %fills data storage
       if idx2 < chunk_size
        idx2 = idx2 + 1;
        Rcvd_2(idx2) = this_byte;

      %as it fills data storage will start in Rcvd_1
      else
        %While Rcvd_2 is filling i want to clear variable Rcvd_1
        Rcvd_1 = zeros(1, chunk_size, 'uint8');
        idx1 = 0;

        %as it fills data storage will start in Rcvd_1
        idx1 = idx1 + 1;
        Rcvd_1(idx1) = this_byte;
      end
    end

You will find that this method is not efficient. Reading one byte at a time has a lot of overhead, and making decisions on two sets of variables has more overhead than making decisions on one variable does. I posted more efficient code a few days ago; see http://www.mathworks.com/matlabcentral/answers/290111-problem-with-serial-port-communication#comment_373272