MATLAB Serial driver testing

The TCP/UDP/IP Toolbox can also be used to interact directly with SITL serial ports. This allows MATLAB to be used to replicate a sensor protocol fore testing and debugging ArduPilot drivers. Unlike previous examples TCP is used and two way communication is possible. By default SITL uses ports 5760 to 5763 for serial ports 0 to 3. The appropriate SERIALx_PROTOCOL parameter should be set to the driver being tested, baud rate is not used. Such a MATLAB tool greatly speeds up development of drivers removing the need to flash and test on real hardware.

This is a example used to send a NMEA string from simulated water speed sensor:

clc
clear

% This is a example of using MATLAB to test a sensor drive using TCP
% we send a NMEA messages at 1hz, note that this assumes that SITL is
% running at real time.

% NMEA is a basic one way protocol but more complex protocols can be
% implemented in the same way

% Use the same TCP/UDP libbary that is used for MALTAB SITL
addpath(genpath('../../SITL/examples/JSON/MATLAB/tcp_udp_ip_2.0.6'))

% if this dosn't work try the MALTAB SITL example first
pnet('closeall')

% Init the TCP port, 5763 is serial 2
u = pnet('tcpconnect','127.0.0.1',5763);

flipflop = true;
while(true)

    if flipflop
        % send MTW temp message
        water_temp = 10 + randn();
        NMEA_string = sprintf('$YXMTW,%0.1f,C',water_temp);
    else
        % send VHW speed message
        water_speed_knots = 5 + randn()*2;
        water_speed_kph = water_speed_knots * 1.852;
        NMEA_string = sprintf('$VWVHW,,T,,M,%0.1f,N,%0.1f,F',water_speed_knots,water_speed_kph);
    end
    flipflop = ~flipflop;

    % Calculate the correct checksum
    NMEA_string = add_checksum(NMEA_string);

    % send to ap
    pnet(u,'printf',sprintf('%s\r\n',NMEA_string));
    pnet(u,'writepacket');

    % also print to MATLAB console
    fprintf("%s\n",NMEA_string);

    % 1hz (ish)
    pause(1);
end

function NMEA_string_out = add_checksum(NMEA_string_in)
    checksum = uint8(0);
    for i = 2:numel(NMEA_string_in)
        checksum = bitxor(checksum,uint8(NMEA_string_in(i)),'uint8');
    end
    NMEA_string_out = sprintf('%s*%s',NMEA_string_in,dec2hex(checksum));
end