[vcf-midatlantic] Kind of OT: RS-485 to DMX-512

[alan at alanlee.org]

As Ethan pointed out, the trickiest part about DMX512 w/ a UART is 
getting the extended break length right for the cycle restart and 
matching the 250 kbit/s rate. Beyond that, the transport layer matches 
EIA-232/485.

And DMX512 isn't so non-vintage computing related.  I did some faux 
lighting panels for a Thinking Machines CM-2 recently.  The controller 
is built around an ESP32 with BT/Wifi.  I thought about adding support 
for artnet so the 4096 individually dim-able LEDs can be controlled with 
standard DMX universes :)  Have to finish the project in January.  Would 
be a good way for non-technical museum people to setup lighting 
patterns.

-Alan


On 2018-11-30 16:46, Ethan O'Toole via vcf-midatlantic wrote:
>> Trying to get a lighting controller to talk to 1986 vintage 
>> microprocessor based lighting control packs.
> 
> This is my world!
> 
>> The PHY layer of DMX-512 (lighting control protocol) is RS-485.
> 
> Yes. Given that it's 1986, are you 100% sure it's DMX-512? If so you 
> are good.
> 
>> Anyone have code samples that could be used as a starting point, or 
>> should I break down & buy the  USB to DMX-512 cable?
> 
> You can get a cheap ($7) FTDI based USB to RS485 dongle from amazon or
> eBay. The FTDI chip can't natively do the proper break space but they
> have a trick of resetting the chip to get the proper spacing for the
> restart of next set of 512 channels transmitted.
> 
> With this adapter (which is similar to the $50 EnTec OpenDMX) you can
> use free software in windows like FreeStylerDMX or QLC+, or if you
> wish to go the linux route there is the Linux OLA package which can do
> Artnet and 1.31 sACN in and translate over to physical DMX512 (via
> RS485 dongle.) OLA has a web interface that lets you tickle the
> channels with a web fader board, and could easily be scripted.
> 
> At the laser enthusiasts gathering I go to I've done a presentation or
> two on running OLA on a PI to do cheap Artnet/1.31 in over to DMX512.
> I can dig up the slides.
> 
> Actually, since the presentation is on the evil cloud I just opened up
> access and here is the steps to install the OLA bits on debian/pi:
> https://docs.google.com/presentation/d/1MqJrwKCAL_tw4t-VnQWevSvXTlszwFy-clECES2YwY8/edit?usp=sharing
> 
> 		- Ethan O'Toole