www.pudn.com > SerialGPS.zip > ReadPacketHeader.m

function [id, sz] = ReadPacketHeader(gps); 
    dle = 16; 
    etx = 3; 
    nak = 21; 
    ack = 6; 
     
    % Three byte header: (DLE, id, size) 
    byte = fread(gps, 1); 
    if (byte ~= dle)  
        WritePacket(gps, nak, 0); % Send NAK, packet not received 
        error(['Expecting DLE at head of incoming packet, received ASCII ', num2str(byte)]); 
    end 
     
    id = fread(gps, 1); 
    sz = fread(gps, 1);