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

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Old May 5th, 2017   #1
RobbG
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Default How to handle DMX Footprint overrun

Hi All,

I've just had an interesting question proposed to me by some other people in my company.

How should a responded behave in a situation where the DMX_START_ADDRESS of a device (root or sub-device) is set to a value greater than (512 - DMX_FOOTPRINT)

Should this behavior be the same for both DMX_START_ADDRESS and DMX_BLOCK_ADDRESS?

My current implementation is an LED driver with 12 sub-devices, each containing 4 channels, if DMX_BLOCK_ADDRESS is used to set the start address of the sub-devices so that any have a DMX_START_ADDRESS above 512 they will set their start addresses to 512. Is there any more guidance on best/recommended practice in this situation?

Thanks in advance,

// Robb
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Old May 5th, 2017   #2
ericthegeek
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This is a common problem. I've seen lots of 30+ slot devices that let you address them to slot 512.

For DMX_START_ADDRESS, it's really up to the implementer and what makes sense for that specific device. Can the device be useful if you only have access to some of its slots?

For a 12-channel dimmer pack, you might want to allow it to be patched to slot 507 just in case someone wants to use the first few dimmers at the end of the universe. But for a 12-slot moving light should probably NACK it because you can't meaningfully control the fixture using only a sub-set of its slots.

For DMX_BLOCK_ADDRESS, that PID opens up all kinds of nasty corner cases like the ones you've described. In my opinion (and this is only my opinion, it's not widely shared by others) you should not implement Block Address. If a fixture needs to be addressed linearly, then the controller is in a better position to do it. The only advantages of Block Addressing arethat you save a few SET requests when you're setting up a rig, and it can also make life a bit easier for Extremely Simple controllers that make it difficult to configure sub-devices.
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Old May 8th, 2017   #3
RobbG
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Quote:
Originally Posted by ericthegeek View Post
The only advantages of Block Addressing arethat you save a few SET requests when you're setting up a rig, and it can also make life a bit easier for Extremely Simple controllers that make it difficult to configure sub-devices.
That's the exact reason we've put it in there, our products are designed for installation and the majority of electricians installing our products use small controllers that don't support sub-devices properly if at all.

Are there any small tool type controllers out there (not requiring a laptop or desk to run them on) which have good sub-device support and support for the E137-1 PIDs?
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Old May 8th, 2017   #4
ericthegeek
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The DMXter4 family supports Sub-Devices and all of the E1.37-1 PIDs (including Block Address).

(Full Disclosure: I have worked for Goddard Design)
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