Technical Support

OK The DMX USB PRO on my Windows 11 PC shows up as a serial port (COM2).  All I need is to output over DMX 2 bytes at a time, the channel number and the value.  I assumed this should be really easy. Looks like you send to the serial port 7E followed by some "label value" of which I cannot figure out, followed by two bytes indicating the message length (in this case 2 bytes) LSB=2 then MSB=0, then the message (in this case 2 bytes) followed by E7. Seven bytes total, but it does not work. Can anyone help?

Mark

OK After a LOT of pulling my hair out.......I have found that the ENTTEC API 70304 PDF file is wrong.

It states that to output your DMX values for your "Universe" as Start of message delimiter, hex 7E, followed by the Label to identify type of message (=6 for the DMX Universe), followed by Data Length LSB, then Data Length MSB, followed by the bytes for the DMX values by channel order, followed by the end of message delimiter, hex E7. This is incomplete as there is an extra byte required called the "startcode byte". 

So the correct data stream is:

Hex 7E, followed by the Label to identify type of message (=6 for the DMX Universe), followed by Data Length LSB, then Data Length MSB, then startcode byte=00, followed by the bytes for the DMX values by channel order, followed by the end of message delimiter, hex E7.  I have also found that you either output channels 1-256 or channels 1-512.  No other number for the universe worked for me.

Here is the output to the virtual COM port for a 512 channel universe:

7E + 6 + 1 + 2 + 0 + 512 bytes (values for ch's 1-512)  + E7

Hope this helps someone

Just to clarify the label=6 does mention the startcode in it's description but does not mention that the startcode=0

Sorry I did not quite get your issue. DMX USB PRO has resources at the web site https://www.enttec.com/product/dmx-usb-interfaces/dmx-usb-pro-professional-1u-usb-to-dmx512-converter/ 

You can find the .NET working sample there. Its fully working & open source.

Do not understand what you are saying....I can send either all 256 bytes (channels) or 512 Bytes to the DMX Pro but cannot send any other number.  Problem is I want to create a strobe on ONE channel only but still have to send the whole universe to the DMX PRO. I clicked your link and do not see and .NET working examples, but I do have it working.

Bought two DMX USB PRO units.....Yes they do work fine with the limitations I mentioned above.  Ended up with the Lixada USB to DMX devices only $29.  I can output approx the same speed to the lights.  The ENTTEC's may have better ESD/transient protection but unfortunately I cannot see any other advantages.  If I could just output to one channel to create a strobe I would be happy, but I always have to output the entire universe,  Slows things down when none of the other channels have changed.

I'm questioning the accuracy of the API documentation too, but in a different, but similar way.  Using the ENTTEC DMX USB PRO to receive DMX data from a controller into my MacOS application, I always see, "7E 05 C2 00 00 00 00 1E FF....."     The 1E FF are channels 1 and 2 from the controller set to 30 and 255, so this confirms the 1E is the start position in the Frame of channel 1.  So then, what are the extra 00 00 bytes?     version 1.44 of ENTTEC's api documentation says what's discussed above, so I'd only expect to see the "7E 05 C2 00 00" and then my 1E FF....    why the extra two bytes?   those are undocumented and I"m not sure if I should develop my parser to always expect those or not?       

@ENTTEC - I know you don't supply or provide technical assistance for developers, but you should be able to verify your API documentation.   Can you explain the above, please?   

Hello Jason.

These two extra bytes always there. We don't use them very much. Maybe, it will be changed in the future but its barely possible.

For DMX USB Pro Mk2 it will be 3 bytes there.