> 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).

This is on purpose. When the frontend is idle, it loops over the slow control 
equipment as fast as possible. This way, you see changes in your hardware very 
quickly. I see no reason to waste CPU cycles in the frontend when there are 
better things to do like reading slow control equipment. Presume you have the 
alarm system running, which turns off some equipment in case of an over 
current. You better do this as quickly as possible, not wasting up to 9 
seconds each time.

The 9 seconds you mention are for reading *EVENTS*. You have double 
functionality: First, reading the slow control system, writing updated values 
to the ODB, where someone else can display or evaluate them (in the alarm 
system for example). Second, assemble events and sending them with the other 
data to disk or tape. Only the second one gets controlled by RO_RUNNING and 
the 9 seconds. You can see this by the updating event statists on your 
frontend display, which increments only when running and then every 9 seconds.

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

There is some information at

http://midas.triumf.ca/doc/html/Internal.html#Slow_Control_system

and at

http://midas/download/course/course_rt03.zip , file "part1.ppt", expecially 
page 59 and page 62 "writing your own device driver".

So what you are missing for your application is a "device driver" for your 
multimeter. The only function it has to implement is the function CMD_INIT 
where you initialize the RS232 port, and the funciton CMD_GET, which sends 
a "R" and reads the value. Now you have two options:

1) You implement RS232 calls directly in your device driver

You link against rs232.c and directly call rs232_init() at the inizialization, 
then call rs232_write() and rs232_read() where you read your 14 ASCII 
characters.

2) You call a "bus driver" in your device driver

This method makes the device driver independent of the underlying transport 
interface. So if your next multimeter accepts the same "R" command over 
Ethernet, you can just replace the RS232 bus driver by the TCPIP bus driver 
without having to change your device driver. But I guess that method 2) is not 
worth for such a simple device like your multimeter.

So take nulldev.c or dastemp.c as your starting point, put some RS232 
initialization into the init routine and the communication via "R" into 
the "get" routine. The slow control frontend, driven by mfe.c, should then 
regularly read your multimeter and the value should appear in the ODB. Take 
the examples/slowcont/frontend.c as an example, and adjust the multi_driver[] 
list to use your new device driver (instead of the nulldev).

I would like to mention that the usage of midas only makes sense for some 
experiemnts which require event based readout, using VME or CAMAC crates. If 
your only task is to read out some devices which are called "slow control 
equipment" in the midas language, then you might be better of with labview or 
something.

I am just starting to explore MIDAS, i.e. reading the manual and trying 
some examples. For the moment I would like to make a simple frontend that 
access a portable multimeter through RS-232 port. I think this could help 
me understand how to access hardare inside MIDAS framework. Initially I've 
started from the MiniFE.c example and tried to initialize the serial port 
on run start transition and build a readout loop in the main function. I 
know that this is not a full frontend but I was just interested in getting 
some experience with the drivers available in the distribution, in this 
case RS-232. The portable multimeter is very simple in principle, one just 
has to configure the port settings and then send character 'R' and read 14 
ASCII characters from the device. Unfortunately I could not understand how 
to invoke the driver services so I changed and started again with the 
slowcont/frontend.c example. From this example and after reading the "Slow 
Control System" section in the MIDAS manual I think that all I need to do 
is to define my own equipment structure based on the multi.c class driver 
with a single input channel (and replace the null driver with the RS-232).

Here I got stuck. I see from the code source that there is a relationship 
between drivers at all levels (even bus) and the ODB but I don't yet fully 
understand how they work. Actually for a couple of days now I am in a loop 
going from class to device to bus and then back again to class drivers 
trying to see how to create my own device driver and especially how to call 
the bus driver. It could be that the framework is invoking the drivers and 
the user just has to configure things ... up to now I didn't dare to look 
at the mfe.c.

Is there a more detailed documentation about slow control and drivers then 
the MIDAS manual? What is the data flow through the three layers system for 
drivers? What is the role of the framework and what is left to the user 
choice?

Thanks

> I want midas alarms to go off when I cannot ping arbitrary remote hosts. Is
> there is easy/preferred way to do this? K.O.

There are "internal alarms" with type AT_EVALUATED. Just find a program 
where you can put some code which gets periodically executed (like the idle 
loop in the frontend), and so something like:

DWORD last = 0;

  if (ss_time() > last+60)
    {
    last = ss_time();

    /* do a ping via socket(), bind() and connect() */
    ...

    if (status != CM_SUCCESS)
      al_trigger_alarm("XYZ Ping", str, "Warning", 
                       "Host is dead", AT_INTERNAL);
    }

Pierre does the same thing in lazylogger.c, just have a look. I don't know 
how to do a ping correctly in C, I guess you have to send an UDP packet 
somewhere, but I never did it. If you find it out, please post it.


 

1) Prior upgrading midas to 1.9.3, make sure you've saved your ODB in ASCII
   format using "odbedit> save my_odb.odb", as the internal structure is
   incompatible with previous version. You will be able to restore it once
   the new odb is up using "odbedit> load my_odb.odb".

2) since version 1.9.2, the analyzer supports ROOT and PAW packages.
   The general Midas makefile build the analyzer core system mana.c
   differently depending on presence of the environment variable $ROOTSYS.

   In the case $ROOTSYS is not defined, the Makefile will create:
   ~/os/lib/mana.o, build for NO HBOOK calls.
   ~/os/lib/hmana.o, build with HBOOK calls for PAW analyzer
    (requires /cern/pro/lib to be present).

   In the case $ROOTSYS is defined and pointing to a valid root directory:
   ~/os/lib/mana.o, build for NO HBOOK calls.
   ~/os/lib/rmana.o, build for ROOT analyzer.

3) Since 1.9.2, the ~/examples/experiment contains the ROOT
   analyzer example instead of HBOOK. The local Makefile uses the source
   examples and the ~/os/lib/rmana.o for building the final user
   application.
   
   The previous HBOOK(PAW) analyzer has been moved into ~examples/hbookexpt
   directory. The analyzer is build using the ~/os/lib/hmana.o 

4) A new application "rmidas" is available when the system is build with
   ROOT support. This application is an initial "pure" ROOT GUI implementing
   TSocket for remote ROOT histogram display. 
   Once a ONLINE ROOT analyzer is up and running, by invoking "rmidas"
   you will be prompt for a host name. Enter the node name hosting the
   analyzer. You will be presented with a list of histogram which can
   be display in a ROOT frame environment (see attachment). 

5) The support of ROOT is also available for the logger by changing  
   the data format and the destination file name in the ODB structure.
   This option will save on file the Midas banks converted into ROOT Tree.
   This file can be opened with ROOT (see attachment).

------- ODB structure of /Logger/Channels/0/Settings
   [local:midas:R]Settings>ls
    Active                          y
    Type                            Disk
    Filename                        run%05d.root    <<<<<<<<< new extension
    Format                          ROOT            <<<<<<<<< new format
    Compression                     0
    ODB dump                        y
    Log messages                    0
    Buffer                          SYSTEM
    Event ID                        -1
    Trigger mask                    -1
    Event limit                     0
    Byte limit                      0
    Tape capacity                   0
    Subdir format                   
    Current filename                run00211.root
-------   

.

I want midas alarms to go off when I cannot ping arbitrary remote hosts. Is
there is easy/preferred way to do this? K.O.

Dear Midas users,

As you certainly aware, ELOG (Electronic Logbook) has been written
by Stefan Ritt and its functionality is part of the Midas package too.
This web site using Elog is replacing the W-Agora Forum previously setup.

You will need to register to this forum in order to gain Write access and 
possible Email notification.

We would like to encourage you to post your questions or comments at
this Midas Elog site instead of using private Email to the authors as your 
remarks are surely of interest to the other users too.