ISO3082: DMX RDM SPLITTER

philippe cavalier

Prodigy 120 points

Part Number: ISO3082
Other Parts Discussed in Thread: SN7414

Composition1.pdfgood morning everybody

i need to build a DMX RDM SPLITTER with ISO 3082

this SPLITTER must be completly integreted on a DMX RDM 4 ch board

this board use an ISO 3082 and run well

i can build a classi DMX SPLITTER but not RDM

i'm not avaibale to create this kind of schematic

i need your help

best regards philippe

over 6 years ago

0 Dan Kisling over 6 years ago

TI__Expert 6195 points

Hi Philippe,

Welcome to the E2E community!

I would like to support you for this DMX RDM application, but I'm going to need a bit more information.

Could you re-upload a higher resolution version of the schematic you attached? When I downloaded the file it opens up too blurry to read anything.
If possible, could you give me a simple block diagram for your system?
What are the key system specifications for this system?

Best regards,

Dan

0 philippe cavalier over 6 years ago in reply to Dan Kisling

Prodigy 120 points

hello DAN
thanks for your answer
i will make documents for you as soon as possible
best regards
philippe

0 philippe cavalier over 6 years ago in reply to philippe cavalier

Prodigy 120 points

DMXRDM - BLOC.pdfDan, this is the documents

i guess you could help me

best regards

philippeDMXRDM.pdf

0 Dan Kisling over 6 years ago in reply to philippe cavalier

TI__Expert 6195 points

Hi Philippe,

Thanks for re-attaching the files. They are opening up fine for me now.
So, as I understand it, you know how to create a DMX 512 splitter, but you do not know how to make it DMX RDM compliant. Is that correct?

Best regards,
Dan

0 philippe cavalier over 6 years ago in reply to Dan Kisling

Prodigy 120 points

hello DAN

yes is that

i already make a proto with 2 * ISO3082 + SN7414, this run, but i need to put one or more ISO3082

hope you could help

best reagrds

philippe

0 philippe cavalier over 6 years ago in reply to philippe cavalier

Prodigy 120 points

dear DAN

this is the schematic of the prototype

it means run, on one DMX out

the two others not tested yet

my problem, is to be sure that the RDM fonction run correctly

see you and best regards

SPLITTER DMX RDM - 3 X ISO3082 - 09032018.pdf

0 Dan Kisling over 6 years ago in reply to philippe cavalier

TI__Expert 6195 points

Hi Philippe,

I'm going to need a few days to consult with the correct experts and give you a good recommendation. Is it okay if I get back to you on Thursday?

I believe the biggest difference for RDM compliance is the biasing, but I would like to check with some other engineers.

In the meantime I would check out this app note on RS-485 Design Guidelines if you haven't already read it.

I also found this forum that discusses the RDM physical layer. I cannot vouch for the recommendations on there and I haven't read through it all, but it may be an interesting read and / or steer us in the right direction.

Best regards,

Dan

0 philippe cavalier over 6 years ago in reply to Dan Kisling

Prodigy 120 points

hello DAN
thanks for you answer
i will wait you for good news
i work on my prototype and try to find and resolve my need by myself too
many thanks for your help
RDM is hard for me to understand correctly

see you

0 Dan Kisling over 6 years ago in reply to philippe cavalier

TI__Expert 6195 points

Hi Philippe,

Thank you for your patience!

I forsee some issues with the last schematic you sent me. I could be thinking of this wrong, but I think the solution you are using will not prevent more than one slave from communicating back to the master at a time.

I was able to find a TI Design that may be able to help though. Please take a chance to read through the Bidirectional RS-485 Fan-Out Hub Reference Design. I think this topology will ensure that only one slave is communicating to the master at a time.

To take this one step further and ensure that this is RDM compliant, I suggest reading through ANSI-ESTA E1.20 2010 - Entertainment Technology - RDM Remote Device Management Over DMX512 Networks. Here is a link to the ESTA standards page - you should be able to download the standard for free.

The first thing that jumps out at me in the standard is the biasing network (see Figure 2-1: Command Port Reference Circuit on page 6 of the standard). This should probably be implemented in the TI Design I linked in order to make it RDM compliant. If you look through the schematic in the TI Design (page 11 of the TI Design) there are resistors in the correct location (R2, R5, R9, R16, R18, R20) but they are listed as DNI (do not install). These would have to be changed to 562 Ω 2%. Additionally R3, R13, R19 would have to be changed from 120 Ω to 133 Ω 2% so that the resistor in parallel with R1 + R2 would equal 120 Ω.

There may be other modifications required to ensure that your design is RDM compliant but these are my first thoughts.

Let me know if you have any questions!

Best regards,

Dan

0 philippe cavalier over 6 years ago in reply to Dan Kisling

Prodigy 120 points

Hello dan
many many thanks
i beleive those informations will help me
i have to draw now my schematic
build a PCB and test
i will inform you for all

thanks thanks
philippe

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ISO3082: DMX RDM SPLITTER