Finally!

It used to be that we’d write the pixel’s DMX address in firmware, then compile and program each PIC.  It worked well but got tedious.

Several thousand pixels later, we’ve got field-programmable source code up and running.

Short version: the PIC listens for an alternate (non-zero, dimmer data always is zero) start code in the DMX stream.  That start code is followed by a special packet of data which contains, among other things, the new start address plus a checksum.  The chances of this particular packet occurring naturally in your lighting rig are one the order of 1 in 2^80.  That’s a 1 followed by 24 zeros.  At the time of this writing, this number is slightly higher than the new US national debt.

‘Programming’ packets can be sent at any time.

The new address is, of course, stored in the processor’s permanent memory.

The address is also displayed by the pixel on power-up. The red LED flashes once (.2 S duration) for each ‘hundred’ in the pixel’s address or once (.6 S duration) if there are no hundreds.

Likewise for green / tens and blue / ones.

Channel 1 = long | long | short

Channel 12 = long | short | short short

Channel 304 = short short short | long | short short short short

etc.

So now, all pixels can be factory programmed with the same firmware.  This saves us a tremendous amount of time.

Firmware works for point source, ‘mini’ and ‘classic’ pixels and is totally backwards-compatible with anything we’ve ever shipped.  It will also work in 3-channel mode on the through-hole DIY pixels.  Haven’t had time to mess with the 5-channel version.

Contact us for a .hex file if you want to re-burn your own pixels.  Or send ‘em back and we’ll be happy to re-flash them with this new code.  Programmers are $46 and will be available soon in the online store.

Watch it work in the clip below. Click the arrows in the bottom right corner of the video frame for a full-screen version.

Setting Pixel Addresses in the Field from Engineering Solutions Inc on Vimeo.”>

Boring technical bits:

A normal DMX packet looks something like this on a ’scope:

BREAK 0 X X X X X X X

Where 0 is the start code, which is then followed by between 1 and 512 8-bit channel values.

Our pixel programming packets have 11 bytes and look like this:

BREAK P I X E L S HH LL CHECK 0xFF

‘P’ is the upper-case ASCII character having a hex value of 0×50. ‘I’ is 0×49, etc. HH is the high byte of the new address. LL is the low byte of the new address. CHECK is the 8-bit sum of the high and low address bytes, overflow ignored.

Programming packets which don’t precisely match this format are rejected.

The pixel firmware doesn’t currently error-check the new address, so values between 513 and 65535 are technically valid. They’ll just never light up in any production lighting rig. However, the programmer firmware is range limited to [1 510]. What good would it do to park a 3-channel pixel at 512?

Peter Jones of Mountain View Staging was kind enough to bring a video camera over late last week.  Below are a couple video clips of the point source pixels in action.

Point Source Pixels from John Chapman on Vimeo.

Point Source Pixels – Zoomed In from John Chapman on Vimeo.

What a day!  This morning I drove downtown to get another 200′ of power and data cable.  I’d previously used 400′ of each for the two lower rooflines, the arch and the garden lanterns.

I finished and tested a second 8-way DMX splitter, because the upper and lower runs are assigned to separate universes.  Then, I weathersealed the remaining 100 or so pixels for the three upper runs.  

We started installing at 5:30 and were finished a few hours later.

The test pattern we ran during installation – and which is shown below – toggles between green with red sparkles, red with green sparkles and blue with white sparkles.

All told there are about 200 point source pixels and 19 ‘classic’ pixels mounted in the garden lanterns.

Click a photo once for medium size, then a second time to see in a larger size.

Will post video clips once I’ve found a 3-CCD camera that has decent dynamic range.

Here are some pictures I grabbed halfway through the installation.  

The low parts of the house are done.  The high parts of the house are terrifyingly out of reach.  Will work on those later this week.

There are 100 point source and 19 standard pixels in the garden lanterns installed so far.  That makes 357 channels of DMX-512.

Click a photo one for medium size enlargement, then a second time to see it full size.