The multimeter device is indeed to simple to use MIDAS but I am just trying 
it as a learning experience. The DAQ system to develop involves VME crates 
and general purpose I/O boards. The slow control part, especially accessing 
the I/O boards seem to me more complex then the VME access. I want to 
understand very well the "correct" way of using the MIDAS slow control 
framework before starting the project.

I chose the second method and created a meterdev.c driver (essentially a 
copy of the nulldev.c) where I changed the init. function and the get 
function. I am not sending a "INIT ..." string because for this device it 
is useless. In the get function I send a "D" and read my string. I changed 
the frontend of the example to have a new driver list (in the first try I 
eliminated the Output device but the ODB got corrupted, I guess the class 
multi needs to have defined output channels). The output channel is linked 
with nulldev and null (I guess this is like if they would not be present).

The result is strange because the get function is called all the time very 
fast (much faster then the 9 seconds as set in the equipment) and even 
before starting the run (I just put the flag RO_RUNNING).

Thanks for any help

//********************************************************************************************
//
// Name:		frontend.c
// Created by:	Razvan Stefan Gornea
//
// Contents:	Slow Control frontend for a portable multimeter
//
// Log:			2004-01-15 14:22
//				Writing down initial code.
//
//********************************************************************************************

#include <stdio.h>
#include "midas.h"
#include "class/multi.h"
#include "device/nulldev.h"
#include "meterdev.h"
#include "bus/null.h"
#include "bus/rs232.h"

// globals variables

// frontend name
char *frontend_name = "Slow Control";
// frontend file name
char *frontend_file_name = __FILE__;
// frontend loop
BOOL frontend_call_loop = FALSE;
// frontend display refresh
INT display_period = 1000;
// maximum event size in bytes
INT max_event_size = 10000;
// maximum event size for fragments in bytes
INT max_event_size_frag = 5*1024*1024;
// buffer size in bytes
INT event_buffer_size = 10*10000;

// equipment list

// device drivers
DEVICE_DRIVER multi_driver[] = {
	{"Input", meterdev, 1, rs232, DF_INPUT},
	{"Output", nulldev, 1, null, DF_OUTPUT},
	{""}
};
// equipment list
EQUIPMENT equipment[] = {
  { "Multimeter",         /* equipment name */
    11, 0,                /* event ID, trigger mask */
    "SYSTEM",             /* event buffer */
    EQ_SLOW,              /* equipment type */
    0,                    /* event source */
    "FIXED",              /* format */
    TRUE,                 /* enabled */
    RO_RUNNING,           /* read when running */
    9000,                 /* read every 9 sec */
    0,                    /* stop run after this event limit */
    0,                    /* number of sub events */
    1,                    /* log history every event */
    "", "", "",
    cd_multi_read,        /* readout routine */
    cd_multi,             /* class driver main routine */
    multi_driver,         /* device driver list */
    NULL,                 /* init string */
  },
  { "" }
};

// routines

INT  poll_event(INT source[], INT count, BOOL test) {return 1;};
INT  interrupt_configure(INT cmd, INT source[], PTYPE adr) {return 1;};
// frontend initialization
INT frontend_init()
{
  return CM_SUCCESS;
}
// frontend exit
INT frontend_exit()
{
  return CM_SUCCESS;
}
// frontend loop
INT frontend_loop()
{
  return CM_SUCCESS;
}
// begin of run
INT begin_of_run(INT run_number, char *error)
{
  return CM_SUCCESS;
}
// end of run
INT end_of_run(INT run_number, char *error)
{
  return CM_SUCCESS;
}
// pause run
INT pause_run(INT run_number, char *error)
{
  return CM_SUCCESS;
}
// resume run
INT resume_run(INT run_number, char *error)
{
  return CM_SUCCESS;
}