> bug in init
> -----------
> 
> I used the lv.c class driver, combined with a custom device driver, to control 
> our Keithley2611B source meter. This to set negative voltage on Si detectors.
> 
> In the 'init' routing, the class driver sets the hv:
> 
>   hv_info->demand_mirror[i] = MIN(hv_info->demand[i], hv_info->voltage_limit[i]);
> 
> This fails for negative voltage, as it sets the (negative) voltage limit, instead 
> of the demand voltage. A simple 'fabs' solves this.
> 
> suggestion for 'idle'
> ---------------------
> 
> I let the device do the ramping, not the driver. This also means I have to reset 
> the state of the device (current limit) after ramping. The easiest way to to 
> this, is using CMD_IDLE of the device driver. This is currently not done in the 
> hv.c class driver.

I can't find the line you quote in the class driver. Why don't you make a git pull request
and I will approve it.

The original idea behind the hv driver is that all voltages in the ODB and the class driver are
positive. If you have a negative power supply, then the voltage is inverted at the device
driver level. That's why you have MIN and MAX in the class driver.

Stefan

> > Currently one has to set the required flag in the ODB (e.g., /Programs/Logger/Required) to "y" for the program 
> > to appear on the "Programs page" and being able to start and stop the program easily.
> > 
> > However, if one wants to run with the "Prevent start on required progs" in /Experiment enabled, all the 
> > programs in the "Programs page" need to be running and one cannot have one of them stopped while still 
> > taking a run.
> > 
> > It would be nice to separate these two functionalities: Have a flag that makes the program appear on the 
> > "Programs page" and have a flag that controls the "Prevent start on required frogs" functionality.
> 
> I agree. All the programs should be always visible on the "programs" page, there should be /Programs/xxx/hidden to 
> hide them, and /Programs/xxx/required should be used for "Prevent start on required progs".

Konstantin, since you wrote the current "Programs" page, can you add that feature to the display (well, when you have time). I guess we 
event don't have to change the subdirectory structure (which might lead to incopatibilities), but just show a program if the "Start command" 
is non-null. If there is no start command, it does not make sense to start that program, so it can be hidden.

Stefan

> There is a small bug in the mfe.c initialization for the EQ_POLLED mode. There 
> is a routine where the number of polls fitting in eq_info->period is counted:
> 
> 
>          count = 1;
>          do {
>             if (display_period)
>                printf(".");
> 
>             start_time = ss_millitime();
> 
>             poll_event(equipment[idx].info.source, (INT)count, TRUE);
> 
>             delta_time = ss_millitime() - start_time;
> 
>             ...
> 
>             if (delta_time > 0)
>                count = count * eq_info->period / delta_time;
>             else
>                count *= 100;
>             
>             // avoid overflows
>             if (count > 2147483647.0) {
>                count = 2147483647.0;
>                break;
>             }
>             
>          } while (delta_time > eq_info->period * 1.2 || delta_time < eq_info-
> >period * 0.8);
> 
> As "start_time = ss_millitime();" resets "delta_time" each time, only the 
> "avoid overflows" addition saves the day. 
> 
> start_time = ss_millitime(); show be out of the loop.

Nope.

What I want is to determine how often I have to call poll_event to stay there for a certain time (usually 100ms). So I iterate "count" until I roughly get to my 100ms. Each call to 
poll_event with a different count is a new measurement, therefore I initialize start_time before each measurement. If i do it outside the loop, and kind of incrementally increase 
it, then the whole code inside the loop is added to the measurement which makes it (slightly) wrong.

The whole loop optimization has some background. Polling can be sow (think of talking to a device via Ethernet which can easily take milli seconds). So how often do we poll 
before we do other things in the main look (like looking if a run has been started). If I only poll once, then the average front-end response time would be poor, because I mostly 
look if a run has been started in the main loop. This is not effective. If I poll too often inside the poll_event loop, then the front-end does not react on run stops any more. So 
there is some optimum, and this is set by the polling time of usually 100ms. This ensures that the front-end does optimal polling - without ANYTHING in between - for about 
100ms. But how can I know how often I should poll for 100 ms? As said above, polling can be very fast (reading a memory cell) or very slow (network). The the best method I 
found is to do a calibration at the startup, and this is what the code above does. Maybe there are better ways today, but that code worked nicely in the last 25 years.

Stefan

> Thanks, I misunderstood the loop then. If poll_event(equipment[idx].info.source, (INT)count, TRUE); doesn`t do anything with "count", the loop becomes infinite except for the overflow 
> check. 

Well, the function poll_event() is _supposed_ to use "count" in a for loop as written in the example frontend:

   for (i = 0; i < count; i++) {
      /* poll hardware and set flag to TRUE if new event is available */
      flag = TRUE;

      if (flag)
         if (!test)
            return TRUE;
   }

where "flag = TRUE" must be replaced with the proper hardware check. This can be a VME access, a network TCP exchange with some Ethernet based hardware, or even a mutex check if the events are collected by a 
separate thread in the frontend.

The idea of having the for (i=0 ; i<count ; i++) loop _inside_ the poll_event() function and not outside is the fact that each function call to poll_event() takes time, and we want the minimal possible response time to new 
events. It might be just a micro-second, but having an experiment running at 100 Hz for one year (like Mu3e), this adds up to about one hour per year, which is a considerable amount of precious beam time.

Stefan

> In any case, IMO, mhttpd has no business serving the contents of /root,
> or serving any files outside of the mhttpd user $HOME directory. (but also
> should not serve files from ~user/.ssh, or any other "secret" files, good
> luck making a complete axhuastive list of all secret files that should not be
> served).

I fully agree with Konstantin. mhttpd should only serve files under certain directories. One is the 
midas/resources directory, another is the one defined in the ODB under /Custom/Path. I plan to modify 
mhttpd to only serve these files (and also prevent tricks like putting "../../../" into the URL). This will then 
also fix Andreas' problem.

Stefan

> There is a bug in the string handling when changing ODB string entries via the
> mhttpd (git sha 07dfb83). It truncates the string length in the ODB.
> 
> For instance I create a string with length 32 and set it with odbedit to 'a'.
> Then the string length stays 32, as expected. If the same is done through the
> web-interface, the string length will be truncated to 2.
> 
> This can lead to problems if some frontend has a hotlink to a structure
> containing this string since it will complain about structure size mismatch. 

I know about this problem since last summer. I mentioned it to KO, since it's deep down in his 
JSONRPC code. We had a long discussion, where he kind of insisted that this is not a bug but a 
feature. The ODB should store strings with variable lengths, and thus adapt it according to the 
current string length. This makes some sense, since in the future we plan to put C++ string 
support for the ODB, where strings have dynamically varying lengths. But this will take a while, so 
I asked KO to change the truncation of the strings though the web interface, because this breaks 
many experiments. He did not react so far. Several people complained. Maybe your request will 
help now.

Stefan

> A feature I always missed (or just missed to find in the docu) is the following:
> 1) It would be nice to have a command in odbedit which allows to check how full
> the ODB currently is.
> 2) Even more important: I would like to have an ODB routine which allows me to
> check the fill level of the ODB, and/or a routine which tells me if I would
> create a structure of given size that it still fits in the current ODB or not. 
> The use case is that some clients create on the fly ODB entries and I would like
> to make sure before hand the ODB's remaining space in order not to crash things
> by overfilling the ODB. 

If you do "mem" in odbedit, you see the currently free areas, one for the keys themselves, one for 
the data of the keys. The corresponding C function is db_show_mem. At the moment it outputs the 
list of free blocks as a long ASCII string, but if necessary I can write a variant which returns the 
number of free bytes.

Stefan

> > > A feature I always missed (or just missed to find in the docu) is the following:
> > > 1) It would be nice to have a command in odbedit which allows to check how full
> > > the ODB currently is.
> > > 2) Even more important: I would like to have an ODB routine which allows me to
> > > check the fill level of the ODB, and/or a routine which tells me if I would
> > > create a structure of given size that it still fits in the current ODB or not. 
> > > The use case is that some clients create on the fly ODB entries and I would like
> > > to make sure before hand the ODB's remaining space in order not to crash things
> > > by overfilling the ODB. 
> > 
> > If you do "mem" in odbedit, you see the currently free areas, one for the keys themselves, one for 
> > the data of the keys. The corresponding C function is db_show_mem. At the moment it outputs the 
> > list of free blocks as a long ASCII string, but if necessary I can write a variant which returns the 
> > number of free bytes.
> > 
> > Stefan
> 
> Thanks for the info, and yes a variant of db_show_mem returning the number of free bytes would be just
> prefect!

I made you db_get_free_mem(HNDLE hDB, INT *key_size, INT *data_size)

The first return gets you the number of free bytes for the key area, the second one for the data area (values of keys).

Committed to develop

Stefan

It might have worked some ~5 years ago, but it never really showed the target value of a link, just the 
link itself. I reworked the code now to show both the link and the target of the link, so you can change 
both in the mhttpd ODB page. Should be consistent now with odbedit. Have a look if it works for you.

Stefan

The function mhttpd_init() scans the custom page and installs handlers etc. for each modbxxx 
element. If you create an modbvalue dynamically in your code, this is probably done after you 
called mhttpd_init(), so the function has no chance to modify the dynamically created element.

To fix that, I separated mhttpd_init() into the old init function which installs the header and sidebar, 
and a function mhttpd_scan() which scans the custom page and processes all modbxxx elements. 
Next, I tapped the error you reported, and added an automatic call to mhttp_scan() in case that 
happens. I tried it on a test page and it worked for me. Please give it a try (commit 090394e8).

Stefan

Two options:

1) Do NOT send your events into the ODB. This is controlled via the flag RO_ODB in your frontend setting. For simple experiments with small events, it might make sense to copy each 
event into the ODB for debugging, but if you have large events, this does not make sense. Use the "mdump" utility to check your events instead.

2) Increase the size of the ODB. See the first FAQ here: https://midas.triumf.ca/MidasWiki/index.php/FAQ

Stefan


> Dear expert,
>       I'm developing a frontend and I'm getting this kind of error at each event:
> 
> 10:14:56.564 2018/05/04 [Sample Frontend,ERROR] [odb.c:5911:db_set_data1,ERROR]
> online database full
> 
> If I run the mem command in odbedit I get the result at the end of this post.
> 
> Notice that I need to use an event size which is significantly larger than the
> default one. I don't know if it is relevant for this error. I have in the ODB:
> 
>   /Experiment/MAX_EVENT_SIZE = 900000000
> 
> and in the frontend code:
> 
>   /* maximum event size produced by this frontend */
>   INT max_event_size = 300000000;
> 
>   /* maximum event size for fragmented events (EQ_FRAGMENTED) */
>   INT max_event_size_frag = 5 * 1024 * 1024;
> 
>   /* buffer size to hold events */
>   INT event_buffer_size = 600000000;
> 
> Events seem to be properly stored in the output files, but I'm afraid I could
> get some other problem.
> 
> Thank you for your help,
>          Francesco
> 
> -------------------------------------------------------------------------
> 
> Database header size is 0x21040, all following values are offset by this!
> Key area  0x00000000 - 0x0007FFFF, size 524288 bytes
> Data area 0x00080000 - 0x00100000, size 524288 bytes
> 
> Keylist:
> --------
> Free block at 0x00000B58, size 0x00000008, next 0x000053E0
> Free block at 0x000053E0, size 0x00000008, next 0x00006560
> Free block at 0x00006560, size 0x00079AA0, next 0x00000000
> 
> Free Key area: 498352 bytes out of 524288 bytes
> 
> Data:
> -----
> Free block at 0x000847F0, size 0x0007B810, next 0x00000000
> 
> Free Data area: 505872 bytes out of 524288 bytes
> 
> Free: 498352 (95.1%) keylist, 505872 (96.5%) data

> Uncaught ReferenceError: XMLHttpRequestGeneric is not defined
>     at cs_button (Trend:165)
>     at HTMLInputElement.onclick (Trend:90)  

That code was not written by me, so I'm must guessing here.

Probably the XMLHttpRequestGeneric() is some function hiding browser specialities to create 
AJAX requests. These days most browser understand the standard request

XMLHttpRequest()

so why don't you try to just remove the "Generic"

Stefan

> I would like to store the address of 1-Wire temperature sensors in a device
> driver. However, the supportet data types (as definded around
> include/midas.h:311) do not foresee a type large enough.
> 
> Is there a good reason against this?
> 
> I know that other experiments use this kind of sensor, how do you store the
> addresses? I've noticed that most of the address is just zeroes, but I wouldn't
> like to store just half the address, assuming that half the address is always
> zeroes.

Well, when this code was written, computers had 640kB  and operating systems had 16 bit. What 
you  can do for your 1-wire sensor is to store the address in two values, one 32-bit LSB and one 
32-bit MSB. Or store it in a string with hex representation.

Stefan 

> > Asume you have a variable foo and a link bar -> foo. When you go to the ODB in
> > mhttpd, click "Delete" and select bar, it actually deletes foo. bar stays,
> > stating "<cannot resolve link>". Trying the same in odbedit with rm gives the
> > expected result (bar is gone, foo is still there).
> > 
> > I'm on the develop branch.
> 
> I think I can confirm this. Created a bug report on bitbucket:
> 
> https://bitbucket.org/tmidas/midas/issues/148/mhttpd-odb-editor-deletes-wrong-symlink
> 
> K.O.

I fixed this and committed the change. Took me a while since it was in KO's code.

Stefan

> > Dear experts,
> >               is there any way to launch an executable script on the host computer from the MIDAS 
> > sequencer? If not, is there any interest to develop such a feature?
> > 
> > Thank you,
> >          Francesco
> 
> The SCRIPT command will do that (on the machine running MIDAS). I know it works with either python or
> bash scripts. I tried without success to pass the parameters and I went around by setting ODB entries
> prior to running the script and then access to them within the script.

Passing parameters should work. If it's confirmed to be broken, I'm willing to fix it.

Stefan

> If you run an external script anyway, you can also call "odbedit -c alarm" to
> reset all alarms. Or you could try to set the "Triggered" entry of that certain
> alarm to 0 (again, with odbedit), that could also work.

That would not really help, because you cannot trigger a script AFTER an alarm occurred. Having 
"self-resetting" alarms is actually not a bad idea. I could add a flag "Auto reset" which is false by 
default and can be set to true for this functionality. Will keep that in mind for the next 
development cycle.

Stefan

> I was planning to use the alarm system to display an information banner when a
> certain valve is open, but I would like it to go away again when the valve is
> closed.
> Is there a way to achieve that? Maybe reset the alarm from an alarm script?
> (Seems like a hack...)
> Maybe this could be a useful feature, to be able to define an alarm class that
> resets itself once the condition is no longer met?

Actually you can implement such a thing already now pretty quickly using custom javascript on 
the status page. Just read the valve state regularly from the ODB and dynamically modify the 
status page to show or hide a banner. Look how custom pages work in midas and try to apply 
this to the status page status.html which you find in the resources directory.

Stefan

> Hello Everybody,
> 
> I am a member of a satellite team with a scientific payload and I am considering
> coordinating the payload using MIDAS. This looks to be challenging since MIDAS
> would be implemented on an Xilinx Spartan 6 FPGA with minimal hardware
> resources. The idea would be to install a soft processor on the Spartan 6 and
> run MIDAS through UCLinux either on the FPGA or boot it from SPI Flash. Does
> anybody have any comments on how feasible this would be or perhaps have
> experience implementing a similar system?
> 
> -Devin

While some people successfully implemented a midas *client* in an FPGA softcore, the full midas 
backend would probably not fit into a Spartan 6. Having done some FPGA programming and 
working on satellites, I doubt that midas would be well suited for such an environment. It's 
probably some kind of overkill. The complete GUI is likely useless since you want to minimize your 
communication load on the satellite link.

Stefan

> 
> 
> One can collapse the side panel when looking at history pages with the button in
> the top left, great! We want to see many pages so screen real estate is important
> 
> The issue we face is that when the page refreshes, the side panel expands. Can
> we make the panel state more 'sticky'?
> 
> Many thanks
> Joseph (ALPHA)
> 
> Version: 	2.1
> Revision: 	Mon Mar 19 18:15:51 2018 -0700 - midas-2017-07-c-197-g61fbcd43-dirty
> on branch feature/midas-2017-10

Hi Joseph,

In principle a page refresh should now not be necessary, since pages should reload automatically 
the contents which changes. If a custom page needs a reload, it is not well designed. If necessary, I 
can explain the details. 

Anyhow I implemented your "stickyness" of the side panel in the last commit to the develop branch.

Best regards,
Stefan