Dmx/pc Interface

[Ben]

I have found a circuit diagram for a DMX dongle to connect to the serial port of a pc and wondered if anyone else has built their own??

 

if so did it work well and would you be willing to share the circuit diagram? just dont liek the idea of conecting the device to my pc without knowing if this is anything like ones other s have built as im not in a positin to replace the pc if I destroy this one.

 

thanks in advance for all the responses I am sure I will get

Ben

[gareth]

Tell ya what, post the circuit diagram here, I'll knock it together when I get a minute and try it out - I have a couple of old PCs in the office here that I have no qualms whatsoever about blowing up.

[Thirdtap]

Are you going to tell Doris is the office that you are going to turbo charge her PC are just film the results?

[NickLee]

I have found a circuit diagram for a DMX dongle to connect to the serial port of a pc and wondered if anyone else has built their own??

 

if so did it work well and would you be willing to share the circuit diagram? just dont liek the idea of conecting the device to my pc without knowing if this is anything like ones other s have built as im not in a positin to replace the pc if I destroy this one.

 

thanks in advance for all the responses I am sure I will get

Ben

I've all the bits for one in a box upstairs.

Never got round to assembling it. I've even got a PCB for it that I got my a former teacher to etch for me using his school's etching tank.

 

--N

[Ben]

I take it from the answers given that no one has made their own.

 

does anyone know of where to find the circuit diagramme for a usb DMX interface? I have one for serial but it can only control 64 DMX addresses, usb cna in theory at least have well over 5 universes althought for my use one will do me hapily for the time being.

 

the site that I am working off for the serial one is: this one

[Brian]

The hardware side is trivial both for serial and usb, you could after all just use a usb to serial converter.

 

The software to do something useful is the harder part.

[Ben]

the software can be downloaded from the site I gave above, and the code is available all over the internet and a programmer freind of mine would be able wo do me what ever else I need.

 

it is not as easy as using a usb to serial converter as the serial conector can only take a set amount of data at a time, the usb however is faster than most people know and 1 usb port can suport thousends of usb devices. this is why it is a much better interface for whatever you can put through it, including the DMX signal. the problem I am having is finding the schematics for a usb interface.

 

hope that all made some sort of sense

 

Ben

[peter]

it is not as easy as using a usb to serial converter as the serial conector can only take a set amount of data at a time, the usb however is faster than most people know and 1 usb port can suport thousends of usb devices.

You could use one USB>serial converter for each universe

 

And there is a limit of 128 devices per USB port, when daisychained.

[Ben]

the limit of 128 devices is only for dasy chained items, if you use a hub as a splitter then you cna litraly put thousends.

 

the problem with 1 usb->serial per universe is that the serial cannot take a univers it can take the first 64 parts of a universe, so you are using 1/8 of each universe and if using Ispots for example thats not even 5 per serial port

[peter]

the problem with 1 usb->serial per universe is that the serial cannot take a univers it can take the first 64 parts of a universe, so you are using 1/8 of each universe and if using Ispots for example thats not even 5 per serial port

There are definatly schematics available for serial devices that produce full 512 channels....anyone?

[ace]

The circit diagram on that page is a parralel not serial device...

 

It is also limited to 64 channels due to the register memory of the 16F84 not the serial bandwidth as you mentioned above... To expand your 'universe' you could simply add aditional pics as a network..

[Ike]

I am thinking that this circuit might do better in a professional environment with some form of isolation, optical isolators on parallel port? Other than that the circuit and assembly code seems to make sense. I havent looked at the VB but im guesing it works.

 

USB is a really awful thing to have to interface with (one of the very few reasons pc's are still made with serial/parallel ports) and would not even consider starting to design an interface.

 

Has anyone tried the RS232/DMX interface card from maplins yet (cat number RP99H)? Seems quite cheep really at £79.99 inc. VAT and the idea of not having to fault find is very appealing.

 

 

Ike

[peter]

Am I right in thinking that the Maplin interface would also work as a 4 channel 0-5v demux? It seems almost too good to be true.

[Brian]

Peter wrote:

Am I right in thinking that the Maplin interface would also work as a 4 channel 0-5v demux?

 

The manual for the Maplin board can be found here Link to Maplin board

 

I have a couple of concerns with it though...

 

1. The serial link to the PC only runs at 9600 baud and uses an ascii protocol , this will introduce a noticeable delay on any changes. Worst case a full update of all 512 DMX channels (eg DBO) will take 3.7 seconds to send to the board.

 

2. I do not think that the unit will transmit all 512 channels. I can't find a definate answer anywhere on that but when reading DMX to send to the PC, the card only extracts the 4 channels assigned to it and sends those to the PC. If it where to be able to transmit all 512 channels it would need 512 bytes of RAM and the micro they use does not appear to contain that much.

 

Ike wrote:

USB is a really awful thing to have to interface with

 

Not anymore. 1 chip and free drivers on the PC which makes the far end look like a serial port which will run at up to 3 Mbps (DMX is only 250kbps).

 

Ike wrote:

some form of isolation, optical isolators on parallel port

 

Far easier to isolate the DMX output to prevent an nasties coming back at you.

 

Peter wrote:

There are definatly schematics available for serial devices that produce full 512 channels....anyone?

 

I reckon it's easier to use the parallel port. Elektor published a design which would do 480 DMX channels, I have it as a pdf which I could e-mail anyone interested. The PCB is available from elektor.

 

ace wrote:

To expand your 'universe' you could simply add aditional pics as a network

 

Except you'd end up with lots of 64 channel universes which you'd have to merge to greater bigger ones.

 

[WARNING] - possible commercial post coming up

 

How much interest would there be in a USB to DMX device, offered as a PCB/kit/pre-programmed micro which you could control youself with a simple programming interface, ie with no software supplied for the PC?

 

The reason for asking is that I have all the necessary bits done to make such a gadget. I would need to do a pcb layout and a bit of documentation. and it would only be worth doing if I covered my costs.

 

[/WARNING]

[peter]

[WARNING] - possible commercial post coming up

 

How much interest would there be in a USB to DMX device, offered as a PCB/kit/pre-programmed micro which you could control youself with a simple programming interface, ie with no software supplied for the PC?

 

The reason for asking is that I have all the necessary bits done to make such a gadget. I would need to do a pcb layout and a bit of documentation. and it would only be worth doing if I covered my costs.

 

[/WARNING]

Provided it wasnt too expensive, I think you could be on to a winner.