%% gpibee_vxi11_demo.m
%
% MATLAB demo talking to an HP 34401A (or any SCPI DMM) over VXI-11
% through a GPIBee, using the Instrument Control Toolbox's visadev()
% interface.
%
% Unlike the Octave port next door (which talks native VXI-11 with no
% VISA runtime installed at all), MATLAB's VXI-11/TCPIP support sits on
% top of VISA -- see README.md for why, and what you need installed.
% Same instrument, same GPIBee, same VXI-11 wire protocol underneath;
% just a different client-side stack.
%
% Run: open this file in MATLAB and press Run, or `run gpibee_vxi11_demo`
% Requires: MATLAB Instrument Control Toolbox, and a VISA runtime
% (NI-VISA, Keysight IO Libraries, R&S VISA, ...) installed separately.

%% ---- configuration -----------------------------------------------------

instrument_ip   = "192.168.3.2";        % GPIBee / instrument LAN address
instrument_name = "inst0,4";            % VXI-11 device name (same
                                         % "inst0,4"-style convention used
                                         % by every other example in this
                                         % project -- see the top-level
                                         % README.md)
resource        = "TCPIP0::" + instrument_ip + "::" + instrument_name + "::INSTR";
read_count      = 100;                  % number of MEAS:VOLT:DC? readings
io_timeout_s    = 3;                    % matches the 3 s timeout used
                                         % throughout this project

%% ---- connect and log -----------------------------------------------------

fprintf("Connecting to %s ...\n", resource);
v = [];
try
    v = visadev(resource);
    v.Timeout = io_timeout_s;
    % writeline()/writeread()'s default Terminator is "LF" ("\n"),
    % matching the LF write/read termination used by every other
    % example in this project.

    idn = writeread(v, "*IDN?");
    fprintf("*IDN?: %s\n", idn);

    fprintf("Reading %d DC-voltage measurement(s) via MEAS:VOLT:DC? ...\n", read_count);
    readings  = zeros(read_count, 1);
    elapsed_s = zeros(read_count, 1);
    t0 = tic;
    for i = 1:read_count
        response      = writeread(v, "MEAS:VOLT:DC?");
        readings(i)   = str2double(response);
        elapsed_s(i)  = toc(t0);
        fprintf("#%3d: %-18s -> %.6f Vdc (t = %.2f s)\n", ...
            i, strtrim(response), readings(i), elapsed_s(i));
    end

catch ME
    if ~isempty(v)
        clear v
    end
    rethrow(ME)
end

clear v   % releases the VISA session -- visadev has no explicit close();
          % the connection is closed when the object is cleared or goes
          % out of scope
fprintf("Connection closed.\n");

%% ---- plot ------------------------------------------------------------

figure;
plot(elapsed_s, readings, "-o");
grid on;
xlabel("Elapsed time (s)");
ylabel("DC Voltage (V)");
title(sprintf("HP 34401A MEAS:VOLT:DC? -- %d readings via %s", read_count, resource));