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RDM General Implementation Discussion General Discussion and questions relating to implementing RDM in a product.

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Old December 16th, 2011   #1
WouterVerlinden
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Default Pixelstring on RDM

Hi all,


assume following product:
- A string of RGB pixels, being RDM compatible
- The string can contain anything between 1 and 100 pixels
- The DMX Footprint can therefore be anywhere between 3 and 300 DMX channels.


What is the most appropriate way of implementing this?

A) Have unique Device Model ID for each possible string length / pixel quantity.
-> The leads to generating 100 different Device Model IDs, each with a static DMX512 footprint
-> The device will then change its Device Model ID when the amount of pixels is modified (by the user)


B) Have a single Device Model ID for all possible string lengths / pixel quantities, and use DMX512 footprint according to string length.
-> This leads to the situation that (for example) device A of this Model ID reports a DMX152 footprint of 150 channels (as it has 50 pixels), whereas device B (with the same Model ID) report a DMX512 footprint of 300 channels (as it has 100 pixels).


C) Have a single Device Model ID for all possible string lengths / pixel quantities, and identify each pixel as sub-device.
-> This leads to the situation that (for example) device A of this Model ID reports that it has 50 sub-devices (as it has 50 pixels), whereas device B (with the same Model ID) reports that it has 100 sub-devices (as it has 100 pixels).


It it allowed for two devices with the same Device Model ID to:
B) Report different DMX512 footprint values
C) Report different Sub-Device Counts


Best Regards,

W
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Old December 16th, 2011   #2
hamish
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Default DMX Footprint

From what I think I understand, you require your devices to operate in different modes, according to the number of pixels being driven.

I would expect an RDM responder to elect its DMX footprint by using different personalities. Each personality that is supported by a responder will have a footprint asscociated with it.

Not sure if I've answered the question that you are asking. Let me know...

Hamish.
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Old December 16th, 2011   #3
ericthegeek
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This situation is is analogous to a dimmer rack with a variable number of field-installable dimmer modules. It's a perfect application for sub-devices. A 96-way dimmer rack can have between zero and 96 dimmers just like your product can have between zero and 150 pixels (or whatever number you've chosen).

The root will have a fixed DMX footprint that will be the same no matter how many elements are installed in the pixel string. You'd use the root device for any master control slots.

Then, each pixel in the string would be a sub-device. A string of 100 pixels would have 100 sub-devices, each with a 3-slot footprint (assuming 8-bit RGB). When you add or remove pixels, the number of sub-devices will change.
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Old December 16th, 2011   #4
sblair
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What Eric said.

I disagree with using Personalities to based on the number of pixels. That would result in hundreds of personalities...a true nightmare. This is exactly the scenario sub-devices exist for. If you could operate the pixel strings with either 3 channels or 4 channels per pixel (i.e. a Master Dim channel for the pixel) then you would want to use Personalities to change between those two modes, but implement the strings as Sub-Devices to handle the changing DMX Footprint based on the number of pixels.
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