%% octave_vxi11_demo.m
%
% No-GUI GNU Octave demo talking to an HP 34401A (or any SCPI DMM) over
% native VXI-11 -- the same wire protocol the GPIBee itself speaks, so
% this connects directly, without needing any vendor VISA runtime
% installed at all (unlike the Codeblocks/Lazarus/Excel examples next
% door, which all go through visa32.dll).
%
% Uses the instrument-control package's built-in vxi11() interface --
% see README.md for why that's the recommended choice over Octave's
% visa() function right now, and for the one real caveat: some
% instrument-control builds are compiled WITHOUT VXI-11 support (this
% is silent and looks nothing like a network problem). Run
% check_vxi11_support.m first if you're not sure about yours.
%
% Run:  octave --no-gui octave_vxi11_demo.m
%
% Note on structure: Octave requires a script's local functions to be
% defined before the executable code that calls them (unlike MATLAB,
% which allows either order) -- that's why the helper functions come
% first here and the actual "main" logic is the block at the bottom.
% The lone "1;" right below is required too: without it, Octave sees
% the file starting with "function" and treats the whole file as a
% function definition instead of a script, silently skipping the
% executable code at the bottom.

1;

%% ---- local functions -------------------------------------------------

function pkg_load_instrument_control()
  try
    pkg load instrument-control
  catch err
    error(["Could not load the instrument-control package: %s\n" ...
           "Install it with:  pkg install -forge instrument-control"], err.message);
  end_try_catch
endfunction

function vi = open_instrument(ip, instr)
  if exist("vxi11") == 0
    error("vxi11() is not defined -- this instrument-control build has no VXI-11 support at all.");
  endif

  try
    vi = vxi11(ip, instr);
  catch err
    if !isempty(strfind(err.message, "doesn't support the VXI11 interface"))
      error(["vxi11(): this Octave/instrument-control build was compiled WITHOUT VXI-11 " ...
             "(RPC) support -- run check_vxi11_support.m and see README.md for details. " ...
             "(original error: %s)"], err.message);
    else
      error("vxi11(\"%s\", \"%s\") failed: %s", ip, instr, err.message);
    endif
  end_try_catch
  % Note: this package version has no separate "set timeout" call for
  % vxi11 objects (io_timeout_s in the main block below is informational
  % only) -- the RPC call itself blocks using the VXI-11 server's own
  % timeout handling.
endfunction

function response = query_instrument(vi, command)
  vxi11_write(vi, [command "\n"]);
  [data, count] = vxi11_read(vi, 4096);
  response = strip_termination(char(reshape(data(1:count), 1, count)));
endfunction

function s = strip_termination(s)
  while !isempty(s) && any(s(end) == sprintf("\r\n"))
    s(end) = [];
  endwhile
endfunction

%% ---- configuration -----------------------------------------------------
instrument_ip    = "192.168.3.2";  % GPIBee / instrument LAN address
instrument_name  = "inst0,4";      % VXI-11 device name (same convention as
                                    % the "TCPIP::<ip>::inst0,4::INSTR" VISA
                                    % resource used throughout the other
                                    % examples in this project)
read_count       = 10;             % number of MEAS:VOLT:DC? readings
io_timeout_s     = 3;              % informational only -- see open_instrument()

%% ---- main ----------------------------------------------------------------

pkg_load_instrument_control();

printf("Connecting to VXI-11 instrument %s at %s ...\n", instrument_name, instrument_ip);

vi = [];
unwind_protect
  vi = open_instrument(instrument_ip, instrument_name);
  printf("Connected.\n");

  idn = query_instrument(vi, "*IDN?");
  printf("*IDN?: %s\n", idn);

  printf("Reading %d DC-voltage measurement(s) via MEAS:VOLT:DC? ...\n", read_count);
  for i = 1:read_count
    response = query_instrument(vi, "MEAS:VOLT:DC?");
    value = str2double(response);
    printf("[%s] #%2d: %-18s -> %.6f Vdc\n", datestr(now(), "HH:MM:SS"), i, response, value);
  endfor

unwind_protect_cleanup
  if !isempty(vi)
    vxi11_close(vi);
    printf("Connection closed.\n");
  endif
end_unwind_protect