It has an RS485 interface on the back. I had been using a PC, and a separate box that did RS232->RS485 to get it to display messages but I feel like I can remove both the PC and the converter box from the equation and just use an Arduino.
The problem is I have no clue how to get to send the text out the 485. I keep searching for sample sketches and I find all sorts of code that looks nothing like what I need. People are doing some crazy things with 485 but nothing is as simple as "push '\000\000\000 Hello World \020' out the 485 port" which is basically what i need to display messages on this thing.
Can anyone give me pointers or suggestions? I found lots of examples of dumping output to an RS232 via an arduino (I dont have a 232 port at the moment) but I would like to remove this extra box if I can just go straight to 485.
Can you point me at any sample code to send output to the serial port then? I don't the code I was messing with was actually sending squat, and since I didn't tell it the RS485 was on pins 6 and 7 anywhere.
RS232 is single ended and used for point to point communications over short distances. RS485 is a differential signal that can be used for multi-drop and over much longer distances. You cannot simply plug RS232 into RS485, you need a converter.
That looks like it might be a rebranded Alpha display. Google for "Alpha 4000 Series"; with a little searching you should be able to find a manual on both the cabling and communications protocol.
niqdanger:
Can you point me at any sample code to send output to the serial port then? I don't the code I was messing with was actually sending squat, and since I didn't tell it the RS485 was on pins 6 and 7 anywhere.
If you aren't using a standard serial port defined for your Arduino type you can use any of the other pins for serial I/O by using the SoftwareSerial library.
I found the documentation for the protocol about color codes/text wipes etc. In fact, I have a quick python script to send a message to the board already via my desktop and its RS232, using a "Spectrum RS232 Converter" that I found with the board. I don't have all the cool effects working, but I can print "Hello World" or some other text, which is the important thing. The plug on the back of the sign says IN RS485 / IN RS232 but I assume since it came with the converter, it needs it. (I've never seen an RS232 in an RJ11 port, so I dunno!)
Unfortunately it looks like part of my issue is the RS485 board has an RJ45 connector on it, whereas the sign has an RJ11. I have to make an adaptor.. time to google search some pinouts.
That's an issue as the two are totally incompatible.
No.
If you ground one of the RS485's differential pair you can squirt RS232 straight in. I can't remember which one of the RS485's input pins so try each in turn.
Don't confuse the protocol with the physical standard. The physical standard defines the signal levels and is totally independent of the protocol, which is what the data means. You can use any protocol over any standard. Here it looks like the protocol used is just simple data bytes.
I think that depends entirely on the particular 485 transceiver chip used. Some can only handle an input to the power supply, some -8 to 13v, some -+15v. So you would need to know what chip is being used.