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## Copyright (C) 2019 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} =} readRegister (@var{dev}, @var{reg}, @var{numbytes})
## @deftypefnx {} {@var{data} =} readRegister (@var{dev}, @var{reg}, @var{numbytes}, @var{precision})
## Read a specified number of bytes from a register of an i2cdev object
## using optional precision for bytesize.
##
## @subsubheading Inputs
## @var{dev} - connected i2c device opened using device
##
## @var{reg} - registry value number
##
## @var{numbytes} - number of bytes to read.
##
## @var{precision} - Optional precision for the output data read data.
## Currently known precision values are uint8 (default), int8, uint16, int16
##
## @subsubheading Output
## @var{data} - data read from device.
##
## @seealso{arduino, device}
## @end deftypefn
function out = readRegister(dev, reg, numbytes, precision)
persistent endian;
if isempty(endian)
[~, ~, endian] = computer ();
endif
persistent ARDUINO_I2C_READREG = 9;
if nargin < 3 || nargin > 4
print_usage ();
endif
if !strcmp(dev.interface, "I2C")
error("@device.readRegister: not a I2C device");
endif
if ~isnumeric (reg)
error ("@device.readRegister: expected reg to be a number");
endif
if ~isnumeric (numbytes)
error ("@device.readRegister: expected numbytes to be a number");
endif
if nargin == 4
if !ischar (precision)
error ("@device.readRegister: expected presision to be a string");
endif
precision = tolower (precision);
if !strcmp (precision, "uint8") && !strcmp (precision, "int8") && !strcmp (precision, "uint16") && !strcmp(precision, "int16")
error ("@device.readRegister: expected pression to be (u)int8 or (u)int16 string");
endif
else
precision = 'uint8';
endif
if (strcmp (precision,'uint16'))
reg = uint16(reg);
if (endian != getEndian(dev.parent))
reg = swapbytes (reg);
endif
reg = typecast (reg, 'uint8');
regsz = 2;
elseif (strcmp (precision,'int16'))
reg = int16(reg);
if (endian != getEndian(dev.parent))
reg = swabytes (reg);
endif
reg = typecast (reg, 'uint8');
regsz = 2;
else
if (strcmp (precision, 'int8'))
reg = typecast (int8(reg), 'uint8');
else
reg = typecast (uint8(reg), 'uint8');
endif
regsz = 1;
endif
% read reg
[tmp, sz] = sendCommand (dev.parent, "i2c", ARDUINO_I2C_READREG, [dev.devinfo.bus dev.devinfo.address regsz reg numbytes*regsz]);
# skip address and and regsz and return the data
out = tmp(3:end);
% convert the outputs
if (strcmp (precision,'uint16') || strcmp (precision,'int16'))
sz = sz/2;
out = typecast (out, precision);
if (endian != getEndian(dev.parent))
out = swapbytes (out);
endif
else
if (strcmp (precision, 'int8'))
out = int8(out);
else
out = uint8(out);
endif
endif
endfunction
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