0. Disclaimer and Copyright.

    dvmd and support, a program for reading cheap multimeters
    Copyright (C) 1997  Dr. J. Hannappel

    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 2 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.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.



1. Overview.
This software is intended to read out digital Multimeters with a 
pseudo-RS232 interface, such as the ones sold by Conrad Electronik,
Hirschau.  These Multimeters have a serial Interface, wich in some 
Versions is decoupled from the rest of the Multimeter with a pair of
optocouplers. The Interface has a fixed Baud-Rate of 1200 Baud, 7 data
bits and 2 stop bits, and sends the value it has just measured as plain
text, containing a unit (Such as mV or KOhm) and a domain description,
like DC or AC. 

The Readout-Software consists of a daemon (dvmd) which is simultaneously
waiting on an arbitrary number of serial lines connected to Multimeters,
and which responds to RPC-Calls from user programms that want to know
the latest measured values.

The dvmd is controlled by a configuration file (/etc/dvmd.config) which
lists the available serial ports and assigns symbolic names to the ones
conected to a Multimeter. This config file (an example is included and will
be installed by make) can be edited with the dvmdconfig program, a tcl/tk 
script. The dvmdconfig program takes the name of the machine whose
/etc/dvmd.config is to be edited as a paremeter and uses rcp's to
retrieve and replace the file.

Two user programs are provided, mostly as examples but also from the 
production needs of our lab, the read_dvm program, wich reads a single
Value and writes it to stdout and the mux_reader program, which is used
to monitor many different values with a single Multimeter and a multiplexer,
that is controlled with some bits of a parallel port.

2. Installaton.
 The programs are tested on linux only, the Makefile
relies on gnu make and a gcc newer than at least 2.3.3 (for the -MG
option). System V IPC is required (for a shared memory section). Also
the rpcgen program is needed to produce the c and yhaeder files from
the dvm_access.x file.  Otherwise nothing special is needed, so
porting to other platforms should be easy (provided they have a working
select()).

To install, use make.
The makefile supports an install and an uninstall target.
*WARNING!
* The install target will create a new user with 
*  uid 199(dvmd) and group 2(daemon).
*

3. Bugs, wishes and commants.
Please send reports and comments to hannappe@lisa2.physik.uni-bonn.de,
they are very welcome.
For new versions see ftp://lisa2.physik.uni-bonn.de/pub/hannappe
or http://lisa2.physik.uni-bonn.de/~hannappe/software/dvmd.html