Dimmable DMX Grinch

[tfmacz]

I saw a posting in the Olsen 595 forum about combining the Ren-C and DMX-Grinch into one converter.

I would love to see this go forward. The Ren-C Dimmable Grinch setup is the slickest system. Compared to the others The simplicity, parts count make this the #1 choice. The only thing that would make it better is the "addressable controller" idea that DMX provides. With the Renard protocol if you lose a controller in the middle of your daisy-chain everything is out of wack. Adding DMX to the dimmable Grinch sorts all that out.

The bit about the DMX dongle being expensive...If someone could write a plug-in that was pointed directly at a serial port then any $5 usb-serial dongle would work with any of the myriad 232-485 converters out there.

[JEC]

The bit about the DMX dongle being expensive...If someone could write a plug-in that was pointed directly at a serial port then any $5 usb-serial dongle would work with any of the myriad 232-485 converters out there.

There's a few wrinkles re: using a serial port to generate DMX directly.

First, it's hard to make the serial port generate a 'break' signal - it doesn't match up with any standard bit or baud timings.

Serial ports like to be fed bytes of data to be transmitted at a specific speed. It's not so easy to generate signals of arbitrary timing.

Second, it may be tricky to find a serial port that runs fast enough. You need 250,000 bits per second (that's 4 microseconds per bit) and a very narrow tolerance for timing error.

At full speed, a DMX transmitter can update 512 8-bit channels about 44 times per second.

That's why most of the computer ==> DMX interfaces out there include a USB interface and a small microcontroller. The processor receives data from the computer and then assembles the DMX packets for broadcast.

The interface will happily do it's job over and over and over, without worrying about the computer's operating system getting in the way or other programs taking momentary precedence.

After design, setup and tooling fees, the parts in one of these interfaces can be had for about $10.

Consider, though, that computer controlled lighting is a very narrow market.

No reasonable company would consider selling these for only $10 - $15 profit unless orders were for thousands or even millions of units.

However... Hardware hackers, who often place no value on their free time, are a different story. :)

[DynamoBen]

JEC is correct in all cases. The other thing to not is the Open doesn't use a micro to generate DMX. It uses a USB to serial adapter. In theory you could use any USB to serial adapter assuming it appeared as a com port in device manager and it wasn't locked to the "standard" baud rates.

I recently purchased a parallax USB to serial adapter for my propeller. It "looks like" the Open device to vixen when plugged in. If I add a 75176 to it I would end up with another open dmx dongle.

I would bet that if you purchased a cheap USB to serial adapter, cracked the case, and soldered up a 75176 it would work. That might be an interesting project.

[tfmacz]

I would bet that if you purchased a cheap USB to serial adapter, cracked the case, and soldered up a 75176 it would work. That might be an interesting project.

I tried that, TheParallax USB uses the FTDI bridge chip. The usb-serial dongles I have use different bridge chips. Can't remember the make. The Vixen DMX plug-in is looking specifically for the FDTI chip:
"Error opening FTD2XX device 0"

But because the OpenDMX is just a USB to RS485 I was hoping that there might be more support for some of the other USB-Serial bridge chips out there...

[tfmacz]

However... Hardware hackers, who often place no value on their free time, are a different story. :)

hmmm....no shortage of those around here, i think.

[DynamoBen]

I have a parallax "Propeller Plug" which looks to be an FTDI chipset also. Now that you mention it I guess the plugin does depend on the FTDI chipset driver. :(

Don't forget that this is also an option. http://www.dlpdesign.com/usb/usb232.shtml

That is what I used for my Open DMX device. Literally I soldered on some resistors and a 75176 and I was ready to go.

[ben]

Ok I am not into all this fancy programming talk etc. I can get by with programing Renard chips but for now that is as far as I have learned.

So can you make a Dimmable DMX board for the olse/grinch or not? Is yes, I would be glad to beta one!

Ben

[fkostyun]

The one part I was able to make a DMX open dongle out of the dlp designs usb adapter

http://www.mouser.com/search/ProductDetail.aspx?R=626-DLP-MM232R

One thing about this adapter is it does appear to have quite a few "capabilities" other than just a usb adapter. (eeprom configurable)

It can xmit RS485 directly from the adapter, it also has multiple clock rates.

[DynamoBen]

So you have this working? If so I will add it to the wiki.

BTW based on a request in another thread I'm building a DMX dongle. I have a proof of concept working on my bench. It will be a multi universe USB DMX dongle when complete.

http://www.christmasinshirley.com/forum/viewtopic.php?t=357

[wbuehler]

Is your adapter like the Pro only cheaper?

Bill

[fkostyun]

Ben, its been working "ok" for me (I haven't tried it a ton)

I am basically tying the txd pin to the input of a 75176 chip.

One thing I find interesting is the outputs of the chip "The FT232R supports all standard baud rates and non-standard baud rates from 300 Baud up to
3 Megabaud" - so it can go quite quickly.

Hopefully I will be able to "play" with this a bit more - and see what it is truly capable of doing.

[DynamoBen]

It would be similar in that it would a USB to DMX interface. Where it is different is multiple universes. Currently I have six working which is 3072 channels. I'm thinking the "released" version would have 4 universes, 2048 values. As far as price the goal is to be below the Pro.

[tfmacz]

I picked up a "Propeller Plug" by Parallax.

I made a little plug-in board with a max485 that matches the 4 pin header on the "propeller plug". Voila, now speaking DMX from the usb port and Vixen recognizes it.

[DynamoBen]

Good to hear, I have a prop plug except I got it with a prop. ;)

There is another option that is a little less expensive. This is what I used to make my first Open DMX dongle, in fact I still use it for my shows.

http://www.dlpdesign.com/usb/usb232.shtml

[RJ]

Ok I am not into all this fancy programming talk etc. I can get by with programing Renard chips but for now that is as far as I have learned.

So can you make a Dimmable DMX board for the olse/grinch or not? Is yes, I would be glad to beta one!

Ben

Ben I don't think your question was answered. No they are working on a DMX dongle to make DMX from the computer cheap. The closeist thing to a DMX dimmable Grinch is the Lynx Freestyle in the Lynx forum.

RJ

[holtm]

The one part I was able to make a DMX open dongle out of the dlp designs usb adapter

http://www.mouser.com/search/ProductDetail.aspx?R=626-DLP-MM232R

One thing about this adapter is it does appear to have quite a few "capabilities" other than just a usb adapter. (eeprom configurable)

It can xmit RS485 directly from the adapter, it also has multiple clock rates.

Any more testing on this? I like the idea. How are you sending the break before each DMX packet? This might be a better question/discussion for the Development Forum.

[DynamoBen]

Any more testing on this? I like the idea. How are you sending the break before each DMX packet? This might be a better question/discussion for the Development Forum.

This looks to be a newer USB to Serial chip. Should work the same as the older version.

The packet and data are created and sent by the PC. In the case of Vixen the plug-in in handling the break before each packet.

I don't know that the development is the best place for researching this. An adventurous soul might want to buy one and solder some resistors and a 75176 (based on the Open DMX schematic) onto it and verify that it works. Then post the results...that assuming this hasn't been tested already.

[holtm]

I just thought the module was directly applicable to the "DMX dongle thoughts" topic http://www.christmasinshirley.com/forum/viewtopic.php?t=2259&postdays=0&postorder=asc&start=0
I noticed that fkostyun was that adventurous soul and didn't want to head that way if he found a dead end.

[DynamoBen]

The "DMX Dongle Thoughts" thread is discussing how to build a device that has a USB interface which connects to a microcontroller which sends out DMX...like the DMX pro.

However there is another way to send DMX with vixen which is the Open DMX dongle. That also uses an FTDI chip (USB to serial) but connects directly to a 75176.

The big difference with the Open DMX dongle the PC generates all the packet information. Where as the DMX Pro and the dongle being discussed in the thread use a microcontroller to generate the packet.

In the end all of the DMX dongles are using some sort of FTDI chipset. The Open uses the USB to Serial, the Pro uses the USB to Parallel, and the one in the thread will end up being USB to Parallel.

[holtm]

Thanks for the info. I understood the forum Serial/Parallel difference. But didn't know the Open used the PC to build the packets and the Pro used the micro. Was there a problem with Open that caused the Pro direction?

This may be a bit off topic, I'm wondering if the USB to Parallel chip would be useful to USB-enable the LED tricks boards??? I might give that a go.

[DynamoBen]

Was there a problem with Open that caused the Pro direction?

Both dongles were designed by Enttec. The Open was an open source design which is why it was first for Vixen. The Pro is their feature rich commerical (closed source) offering. The Pro sends data a bit faster since it doesn't rely on the PC. The wasn't a problem with the Open, think of the Open as the entry level model. (BTW I have an Open)



This may be a bit off topic, I'm wondering if the USB to Parallel chip would be useful to USB-enable the LED tricks boards??? I might give that a go.

Maybe, I'm not real familiar with the project. Its worth looking into I guess. Read through the datasheet very carefully. The parallel dongle is a little different than your PCs parallel port. Take note of the TXE#, RXF#, RD#, and WR pins.