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## Copyright (C) 2022 John Donoghue <john.donoghue@ieee.org>
##
## This program is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
## -*- texinfo -*-
## @deftypefn {} {@var{data} =} read (@var{dev}, @var{target}, @var{address})
## @deftypefnx {} {@var{data} =} read (@var{dev}, @var{target}, @var{address}, @var{count})
## @deftypefnx {} {@var{data} =} read (@var{dev}, @var{target}, @var{address}, @var{count}, @var{serverId}, @var{precision})
## Read data from modbus device @var{dev} target @var{target} starting at address @var{address}.
##
## @subsubheading Inputs
## @var{dev} - connected modbus device
##
## @var{target} - target type to read. One of 'coils', 'inputs', 'inputregs' or 'holdingregs'
##
## @var{address} - address to start reading from.
##
## @var{count} - number of elements to read. If not provided, count is 1.
##
## @var{serverId} - address to send to (0-247). Default of 1 is used if not specified.
##
## @var{precision} - Optional precision for how to interpret the read data.
## Currently known precision values are uint16 (default), int16, uint32, int32, uint64, uint64, single, double.
##
## @subsubheading Outputs
## @var{data} - data read from the device
##
## @seealso{modbus}
## @end deftypefn
function data = read (dev, target, address, count, serverid, precision)
if nargin < 3
print_usage();
endif
if nargin < 4
count = 1;
endif
if nargin < 5
serverid = 1;
endif
if nargin < 6
precision = "uint16";
endif
if ! isnumeric(address) || address < 0
error ("Expected address to be a number.");
endif
if ! isnumeric(count) || count < 1
error ("Expected count to be a positive number.");
endif
if ! isnumeric(serverid) || serverid < 0 || serverid > 247
error ("Expected serverId to be a number between 0 .. 247");
endif
if !ischar(precision)
error ("Expected precision to be a character type");
endif
# precision only used for inputregs and holdingregs
switch (precision)
case {"int16" "short"}
toclass = "int16";
tosize = 1;
case {"uint16" "ushort"}
toclass = "uint16";
tosize = 1;
case {"int32" "int"}
toclass = "int32";
tosize = 2;
case {"uint32" "uint"}
toclass = "uint32";
tosize = 2;
case {"long" "int64"}
toclass = "int64";
tosize = 4;
case {"ulong" "uint64"}
toclass = "uint64";
tosize = 4;
case {"single" "float" "float32"}
toclass = "single";
tosize = 2;
case {"double" "float64"}
toclass = "double";
tosize = 4;
otherwise
error ("precision not supported");
endswitch
switch (target)
case "coils"
# single bit output bits (count = 1 .. 2000)
case "inputs"
# single bit input regs
case "inputregs"
# 16 bit input read regs (count = 1 ... 125)
case "holdingregs"
# 16 bit read/write reg
otherwise
error ("Invalid target type");
endswitch
# number of actual regs to read
toread = count * tosize;
data = __modbus_read__(dev, target, address, toread, serverid);
# Check Word Endian settings, swap word order if required
mbwordendian = get(dev,"WordOrder"); # Modbus word endian
[a,b,cowordendian] = computer(); # machine endian
if ( tosize>1 && (
strcmp(mbwordendian,"big-endian") && strcmp(cowordendian,"L") || ...
strcmp(mbwordendian,"littler-endian") && strcmp(cowordendian,"B") ) )
# swap word order
data = reshape( flip( reshape( data, tosize, count ) ), 1, toread )
end
# type conversion
data = typecast( data, toclass );
endfunction
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