PC communication

[rjgeissinger]

Does anyone know which pins on the serial port are used to communicate with the Light o rama controllers?

[-klb-]

No pins on the serial port are directly used to communicate with the LOR controllers. There is an active signal translator in there to convert the unbalanced RS-232 signal to balanced RS-485. So instead of voltages indicating 1's and 0's, voltage differences are used to indicate the bits. The voltages and impedance used are different as well.

[rjgeissinger]

I'm trying to wire a patch cable to test my lor controllers. your info flies over mt head. sorry

[-klb-]

The USB-485(, and SC-485 use pins 3, 4, 5, & 6 to communicate with the controllers. If you are using twisted pair cable, pins 4&5 should be one pair, and 3 & 6 should be another pair. Straight through ethernet cable is perfect for the application, so you could look up how TIA-568B is wired.

[Tim Fischer]

rjgeissinger wrote:

I'm trying to wire a patch cable to test my lor controllers. your info flies over mt head. sorry

Which interface are you using? You can't connect an LOR unit directly to a PC without an SC-485 or USB-485 interface...

[Max-Paul]

RJ,

Would you please clairify which serial port you are speaking of? Are you talking about the 9 pin connector on the back of your computer? Or are you talking about the jack on your interface module. And if so, which module do you have? Believe it or not, your question leaves so may different possible answers because you did not provide enought info. But if you can answer the above questions. It will allow us to focus on the proper answer.

Tnx

[rjgeissinger]

I was trying to bypass using the LOR serial to ethernet adapter. But it appears there is electronics in their adapter. I figured if I could map the used pins of the serial port and connect them to the appropriate wires in the rj45 jack I could save the 27 dollar cost of the adapter. So now I've ordered the adapter and had to pay an extra 13 buck to ship it separately.



Bummer

[Guest wbottomley]

rjgeissinger wrote:

I was trying to bypass using the LOR serial to ethernet adapter. But it appears there is electronics in their adapter. I figured if I could map the used pins of the serial port and connect them to the appropriate wires in the rj45 jack I could save the 27 dollar cost of the adapter. So now I've ordered the adapter and had to pay an extra 13 buck to ship it separately.



Bummer

That's cheaper than a controller(s).

[Tim Fischer]

I wouldn't be surprised if some of that shipping is refunded. IIRC- the shopping cart has issues with shipping on "light" things like dongles. My coworker had the same issue when he ordered the XLR->Cat 5 converter for DMX use...

[-klb-]

And just to get it in here, in case it is found by search, the LOR buss is not ethernet. It uses the same connectors, and the same cables work, but connecting it to an ethernet device may damage the ethernet device, or the controller, or both.

[bphynes]

-klb- wrote:

No pins on the serial port are directly used to communicate with the LOR controllers. There is an active signal translator in there to convert the unbalanced RS-232 signal to balanced RS-485. So instead of voltages indicating 1's and 0's, voltage differences are used to indicate the bits. The voltages and impedance used are different as well.

When I ordered my starter kit in 2006, I got a 9-pin RS232 DB-9 plug that had an 8-pin RJ-45 connector on the other end. It assuredly has no electronics in it.

Since I tend to loose things like that, and because I have many Cat-5 cables used for serial connections to various things, I have a bag of those types of converters (http://www.monoprice.com/products/product.asp?c_id=104&cp_id=10415&cs_id=1041501&p_id=1153&seq=1&format=2) that I have made with various pinouts for various gear.

The one I got from LOR and several I've made follow EIA/TIA 561 (http://www.zytrax.com/tech/layer_1/cables/tech_rs232.htm#rj45).

These have worked just fine for one and two controllers. I'll let you know if they work with four in a couple of days.

So, after reading this http://www.lightorama.com/SelectAdapter.html and this http://store.lightorama.com/scseco.html, I am firmly convinced that I can spend $28 dollars to get it from LOR or 54 cents from monoprice. Now, I love LOR as much as the next guy, but...

I am also fairly certain that any standard Serial Port (aka "Com1", "Com2", etc.) on a PC can be put into RS-485 with an API call.

I think, therefore, that the translation is being done in the serial port UART, not in the dongle, if you are using a standard serial port.

Obviously, this is completely different if you are using USB (in which the "S" stands for yet another kind of serial).

- Byron

[-klb-]

Assuredly it has no electronics because you have opened it and looked, or just because it is the same size and shape as the common passive connector adapters that many of us have dealt with so often?

While the USB-485B is larger, the USB-485 adapter is in the same size and shape case as the common DB9 to RJ-45 pinout adapters. Does this imply it has no active electronics also?

Are you really confident enough that you are right to go into the season without a SC845 adapter? I'm sure we can find someone to hold yours for you. Are you confident enough to stand behind your assurances, and compensate anyone who follows your advice on this issue if it turns out not to work for them?

You really might want to make a point of testing that your adapter works over the couple of hundred feet and multiple controllers that can be so common for home displays sooner, rather than later.

Also, while RS-485 specifies 3V signaling, depending on the hardware used, RS-232 can be as high as +/- 12V, so there may be some risk of damage to the controllers.

[bphynes]

You win. I have better things to do than post my experience and be attacked. (Oh, and I didn't offer anyone any "advice", just described my experience.)

I'll go back to lurking and calling LOR if I need support.

-klb- wrote:

Assuredly it has no electronics because you have opened it and looked, or just because it is the same size and shape as the common passive connector adapters that many of us have dealt with so often?

While the USB-485B is larger, the USB-485 adapter is in the same size and shape case as the common DB9 to RJ-45 pinout adapters. Does this imply it has no active electronics also?

Are you really confident enough that you are right to go into the season without a SC845 adapter? I'm sure we can find someone to hold yours for you. Are you confident enough to stand behind your assurances, and compensate anyone who follows your advice on this issue if it turns out not to work for them?

You really might want to make a point of testing that your adapter works over the couple of hundred feet and multiple controllers that can be so common for home displays sooner, rather than later.

Also, while RS-485 specifies 3V signaling, depending on the hardware used, RS-232 can be as high as +/- 12V, so there may be some risk of damage to the controllers.

[Tim Fischer]

I'm not attacking you, but please open up the SC485 and have a look. I've seen inside one myself and can assure you there's a little circuit board in there with stuff on it.

You simply cannot convert from RS232 (PC serial) to RS485 (LOR serial) without active circuitry.

[Jeff Sand]

Tim is correct. There are (passive) electronics inside the LOR serial adapter. RS232 and RS485, while similar in function, are separate standards with different electrical characteristics. RS232 is is a non-differential (unbalanced) standard, which specifies +/- 12V from the transmitter, although most modern transcivers work with +/- 5V or +/- 3V.

RS485 is a differential (balanced) standard, meaning 0's and 1's are determined by positive or negative voltate existing between two wires (positive signal and invertited singnal) rather than from signal to ground. Voltage to the common shield can be anywhere from -7 to +12V with at least 200mV differential.

There are other differences as well between 232 and 485 involving load resistance, minimum/maximum current, lenth of wire allowed (~30ft vs. ~4000ft), and number of receivers allowed on the line (1 vs. 32).

RS232/485 are electrical standards, not communication standards (i.e. they only define voltages and currents, not how bits are arranged to form data) and are thus independent of and separate from UARTs. You cannot program a PC serial port to be RS485 because it does not have a differential output.

You could directly wire an adapter to go from the PC serial port to the LOR input jack using RS232 (connecting Tx to D+ and ground to D- and common), and it will probably work, but I wouldn't recommend it in real world. And you really shouldn't try to do it over long distances or anywhere running from indoors to outdoors where a ground loop could be generated.

(Can you tell my EE senior project involved lighting controllers with DMX512?)

-Jeff

[LightORamaJohn]

Jeff Sand wrote:

You could directly wire an adapter to go from the PC serial port to the LOR input jack using RS232 (connecting Tx to D+ and ground to D- and common), and it will probably work, but I wouldn't recommend it in real world. And you really shouldn't try to do it over long distances or anywhere running from indoors to outdoors where a ground loop could be generated.

Jeff is correct, you can wire RS232 transmit to the RS485 jack on an LOR controller and it will work. This seriously exceeds the RS485 driver chip's voltage specs, but it seems to tolerate it and work. We have done no long term testing so we don't recommend this. And, of course, the RS232 port is not differential so noise immunity and distance suffer.

This arrangement is unidirectional so the Hardware Utility can't poll controllers and you can't configure them. Triggers are also unavailable during shows.

[Max-Paul]

So, what you are saying Dan is akin to going deer hunting. You have a rifle, but no bullets, no bolt and no sights of any sorts. So, all you can do is pull the trigger and shout BANG! And hope the deer falls over dead from a serious case of hebee jeebees.

Whats the point of running RS-232? shorter cable lenth restrictions. Open to all kinds of EMI which will stop the show. And as you said a chance of blowing the comm. chip. all of this to save a few bucks... NUTS, just plain NUTS...