Part Number: ISO3082

hello dan

good morning

i come back to you for my DMX RDM splitter

with your i have make a prototype in hard

and there is something not run

i need your help for a second time, because i'm not avaibale to find a good issue

attached the final schematics

it run only if C26 470nf is not present

when i use my RDM console, the discovering of LED project is done and i can change or read some parameter


i think the Frg is not good 

pls help me

best regards


SPLITTER 3 x ISO3082.pdf

9 Replies

  • Hi Phillipe,

    Thanks for following up on this! Glad to hear from you again. Sorry your prototype is not working as intended.

    Could you clarify a few things for me?

    1. Does the board have complete functionality when C26 is not installed? (Communication both ways works fine?)
    2. What does Frg mean?

    Thanks and best regards, 


  • In reply to Dan Kisling:

    hello dan
    so happy to look for you here
    yes when C26 is removed all is ok
    i can send and receive data by / from the RDM console
    frg or Frq, if *Frq it's ic15 frequency output calculed by R17 / C26 from IC15 NA555

    when i look for the TI application note you sent me, it shown that i can make daizy chain
    i build two PCB to test this mode, but not run
    each pcb run correctly

    if you have skype it will be better for me to exchange with you

    it is realy important i solve this problem

    hope you understand clearly what i say, my english is a little old

    best regards
  • In reply to philippe cavalier:

    for your information
    DMX driver send the data to the first SPLITTER on MASTER ic11, the first RGBW led product is connected to SLAVE2 ic10, SLAVE1 ic9 is connected to the second SPLITER on MASTER ic11 and it continue like this
    why this need
    because the cable lenght between splitter can be long and i can't lose data, so it's like a repeater

    hope it's ok for you
    best regards
  • In reply to philippe cavalier:

    Hi Philippe,

    I reviewed your schematics a little more in depth. I have a few follow up questions:

    1. What is the purpose of IC8 on the left hand of your schematic?
    2. What is the purpose of IC12 and the surrounding components? It looks like it is just for driving a status LED. 

    With regards to your layout I also have a few concerns. In order to have galvanic isolation there cannot be any traces or components in the isolation boundary between the left side and the right side of the device. For more information on this please see the layout guidelines in the ISO3082 datasheet and refer to the Digital Isolator Design Guide

    Best regards, 


  • In reply to Dan Kisling:

    CdC4ch DMX RDM - REV G 01072018 - BOTTOM.pdfCdC4ch DMX RDM - REV G 01072018 - TOP.PDFhello dan

    good morning

    thanks for uour help

    IC8 is the IC connected to the CYPRESS processor IC by " RX / RX EN / TX EN / TX"

    as i told you this part run correctly

    IC12 is like you said, for DMX status led

    if the SPLITTER componants no on the board, i keep R26 / R27 / DDKKK3 and the jumper 1 and 2 are instaled, and like this the DMX signal go directly on IC8

    some tests done

    when i connect 2 DMX RGBW led board on the splitter it run, the RDM console read and write data on the RGBW board, but only if C26 not present

    that i do not understand is the operati,g mode of the NA555 without C26, so strange

    your other question was the supply voltage

    there is a complete separted DC supply by DC1 so there is VCC and GND, and VCC DMX and GND DMX, like the net label

    this is what i can say today

    i do not understand why it not run

    i thought a frequency problem donne by IC15 because the application note was not build for DMX signal

    if you need a little movie i can do

    attached the PDF 3D of the final DMX RDM board

    best regards DAN and thanks

  • In reply to philippe cavalier:

    Hi Phillipe,

    Could you try the following:

    1. With C26 installed, probe "EN" and "R master" when trying to communicate. 
    2. With C26 depopulated, probe "EN" and "R master" when trying to communicate. 

    We can take a look at the oscilloscope waveforms and determine if the monostable-configured NA555-timer oscillator is working as we would expect. 

    Best regards, 


  • In reply to Dan Kisling:

    Hi Phillipe,

    I haven't heard from you in a few days. Have you been able to determine the reason your design was not working?

    Best regards,
  • In reply to Dan Kisling:

    hello dan
    good morning
    i very busy for other project and i have no time to work on the splitter
    and it's very urgent i solve the problem
    hope soon
    if you have skype contact, maybe better to chat with you
    best regards
  • In reply to philippe cavalier:


    Have you been able to acquire scope waveforms as suggested by Dan?