NAME

       comedi_data_read - read single sample from channel

SYNOPSIS

       #include <comedilib.h>

       int comedi_data_read(comedi_t * device, unsigned int subdevice, unsigned int channel,
                            unsigned int range, unsigned int aref, lsampl_t * data);

DESCRIPTION

       Reads a single sample on the channel specified by the Comedi device device, the subdevice
       subdevice, and the channel channel. For the A/D conversion (if appropriate), the device is
       configured to use range specification range and (if appropriate) analog reference type
       aref. Analog reference types that are not supported by the device are silently ignored.

       The function comedi_data_read reads one data value from the specified channel and stores
       the value in *data.

       WARNING: comedi_data_read does not do any pausing to allow multiplexed analog inputs to
       settle before starting an analog to digital conversion. If you are switching between
       different channels and need to allow your analog input to settle for an accurate reading,
       use comedi_data_read_delayed, or set the input channel at an earlier time with
       comedi_data_read_hint.

       Data values returned by this function are unsigned integers less than or equal to the
       maximum sample value of the channel, which can be determined using the function
       comedi_get_maxdata. Conversion of data values to physical units can be performed by the
       functions comedi_to_phys (linear conversion) or comedi_to_physical (non-linear polynomial
       conversion).

RETURN VALUE

       On success, comedi_data_read returns 1 (the number of samples read). If there is an error,
       -1 is returned.

AUTHORS

       David Schleef <ds@schleef.org>
           Author.

       Frank Mori Hess <fmhess@users.sourceforge.net>
           Author.

       Herman Bruyninckx <Herman.Bruyninckx@mech.kuleuven.ac.be>
           Author.

       Bernd Porr <tech@linux-usb-daq.co.uk>
           Author.

       Ian Abbott <abbotti@mev.co.uk>
           Author.

       Éric Piel <piel@delmic.com>
           Author.

COPYRIGHT

       Copyright © 1998-2003 David Schleef
       Copyright © 2001-2003, 2005, 2008 Frank Mori Hess
       Copyright © 2002-2003 Herman Bruyninckx
       Copyright © 2012 Bernd Porr
       Copyright © 2012 Ian Abbott
       Copyright © 2012 Éric Piel

       This document is part of Comedilib. In the context of this document, the term "source
       code" as defined by the license is interpreted as the XML source.

       This library is free software; you can redistribute it and/or modify it under the terms of
       the GNU Lesser General Public License as published by the Free Software Foundation,
       version 2.1 of the License.

       This library 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 Lesser General Public License for more details.

       You should have received a copy of the GNU Lesser General Public License along with this
       library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
       Boston, MA 02111-1307 USA.