readpacketheader.m

基于串行接口的GPS驱动程序

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);