Film-Tech Forum ARCHIVE: Datasat AP25 (or AP20) remote control of volume fader

This is topic Datasat AP25 (or AP20) remote control of volume fader in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Karim Benmachiche (Member # 10647) on 05-07-2019, 07:15 AM:

Hello,

We'll be installing a Datasat AP25 within the next 2-3 weeks and I have been reading the manual in detail.

We would like the ability to control the main volume remotely from the floor, for short programs when audio is not at the same volume between movies.

From the manual, I found a detailed ethernet control specification. It also says the AP25 can be controlled via VNC (I think the manual mentions enough about it), or a smartphone application named iRule (I don't own a smartphone so I have no clue what that is), but it doesn't specify anything.

Has anyone already used any of those features?

Is there a way from VNC or the smartphone app to control ONLY the volume fader and and having access to everything else completely blocked?

Has anyone out there written a free/open-source application with graphical user interface to implement the ethernet commands? I guess I could write one, but that would take me more time than I have available before we need to have the feature ready.

Thanks!
Karim

Posted by Sean McKinnon (Member # 612) on 05-07-2019, 08:18 AM:

VNC allows you to control a computer remotely so when you "VNC in" to an AP20 you take control of the main touch screen and can do anything that can be done from the main touch screen.

Posted by Carsten Kurz (Member # 5396) on 05-07-2019, 05:20 PM:

There is a password function, but I think for VNC it is 'all or nothing'. Respectively - as the VNC interface grants full access to the local touch screen, password protection can only block access to configuration options, but will still allow preset change, mute in addition to volume, etc. But that is not such a big deal, as preset change and mute can be very useful as well. That said - using VNC for volume changes on the AP20/25 is not elegant, as you first need to double-tap the fader readout, before you get up/down buttons for volume changes.

There are many ways though to control volume on the AP20/25. You can use serial or ethernet commands, you may also connect a simple toggle switch for volume Up/Down. At our site, we have set up all these options. Control from the server through a web interface, through VNC from our smartphones or noetebooks, and a toggle switch in the auditorium. You need three wires for the toggle switch towards the AP20/25 GPIO connector.

I guess it would be easy to create an app that can only do volume changes. I would be surprised if there isn't one already. Maybe some remote or media control apps can be customized with the proper strings for an AP20/25. iRule is one potential such candidate.

- Carsten

Posted by Karim Benmachiche (Member # 10647) on 05-09-2019, 08:47 AM:

Thanks Carsten, good to know there are other using it the same way we're looking at it.

I have close to zero electronics knowledge, but if I understand correctly, you need a DB25 connector, and if it's three wires, then I guess it's 3 pins on the DB25 that must be connected? From the spec of the AP20/25, I fail to understand which ones it must be. I guess Pin 9 ("GPIO 17 Format Remote Fader
Enable"), but which others?

Also, I don't understand how you can control volume up and down with a toggle switch (unless I don't understand correctly what a toggle switch is) - I thought a toggle switch was either A or B, how do you increase/decrease volume with that?

Sorry if my questions are somewhat silly...

Posted by Carsten Kurz (Member # 5396) on 05-09-2019, 02:31 PM:

Hi Karim,

you can use any of the available GPI, no matter how they are labeled, you can assign one GPI to e.g. increase volume by 0.3, and the other to decrease by 0.3.
We use GPI7 (DB25-7) for up and GPI6 (DB25-6) for down against GND (DB25-12)

So, it's not a simple toogle switch, but a three position toggle switch. Don't know the exact english definition.
It's single pole, On/Off(Center)/On button.
So one direction is volume up, one is volume down. Center is neutral.

e.g. https://www.reichelt.de/wippenschalter-rund-1x-ein-aus-ein-ws-r13-112-daaa-p105445.html?&trstct=pol_8

You could also use two discrete buttons, one for up, one for down, common GND for both.
That's the cheapest way of doing it. On the AP25, you can define events for these two actions.

I suggest you wire not a 3Wire line to that switch, but use a common 4*2 CAT5/6/7, as it offers more future options.

- Carsten

Posted by Karim Benmachiche (Member # 10647) on 05-12-2019, 02:36 AM:

Thanks Carsten, I first thought there was a dedicated pin for the fader, but it makes a lot more sense like this! We should be able to make something easily.

Thanks again!

Posted by Carsten Kurz (Member # 5396) on 05-12-2019, 06:59 AM:

I never found out why there are dedicated fader pin labels in the manual. Maybe at some time they were planning for their own dedicated fader box using these pins. You should probably buy a fully wired D25 cable (e.g. a printer or RS232 cable) and wire all signals to terminal blocks in the back of the rack so, so you have access to all GPIOs on the AP25 for future expansion. The automation module in the AP25 is very powerful.

- Carsten