Serial Communication to a LED sign control box
Alright, I've got a Symon RDU LED sign. Got it for $30 on eBay, problem is, the software for it is $2700. So, I have to come up with the software myself. I also have to come up with the comunication cable myself. I've taken the controller box apart, its got...
a SP232ACP RS-232 controller chip
a SN74LS153N Dual 4-Input multiplexer chip
2 DS8921 Differential Line Driver/Reciever pair chips
a few resistors, a voltage regulator, some diodes, etc
anyways, its got 2 DB25 ports, one for input to the control box from the computer, and an output for another control box in a little daisy chaining action
Now, on the side of this thing it says:
1st Power Supply After PC / Local
Input: RS-232C RX PIN 2
Output: RS-422A TX PINS 13 and 14
So, I'm assuming the input port takes a RS-232C serial cable, DB-25 terminated, and the DTE-to-DCE fits into pin2 on the DB25 port.. Looking at the board, pins 2 and 3 go to the RS-232 controller chip, so I'm also assuming the DCE-to-DTE fits into pin 3 on the DB25... and 1 and 7 are linked, and they go to one of the DS8921 chips, and then to the voltage regulator, and finally to the power connector, to the fuse, and the power supply board, so I guess its a ground...
At the moment, I'm just trying to get this thing connected to my computer, I'll figure out the command set later, I just need a circuitry nut to tell me if I'm right about ANY of this, or if I'm gonna blow myself up.
Lord Skitch
a SP232ACP RS-232 controller chip
a SN74LS153N Dual 4-Input multiplexer chip
2 DS8921 Differential Line Driver/Reciever pair chips
a few resistors, a voltage regulator, some diodes, etc
anyways, its got 2 DB25 ports, one for input to the control box from the computer, and an output for another control box in a little daisy chaining action
Now, on the side of this thing it says:
1st Power Supply After PC / Local
Input: RS-232C RX PIN 2
Output: RS-422A TX PINS 13 and 14
So, I'm assuming the input port takes a RS-232C serial cable, DB-25 terminated, and the DTE-to-DCE fits into pin2 on the DB25 port.. Looking at the board, pins 2 and 3 go to the RS-232 controller chip, so I'm also assuming the DCE-to-DTE fits into pin 3 on the DB25... and 1 and 7 are linked, and they go to one of the DS8921 chips, and then to the voltage regulator, and finally to the power connector, to the fuse, and the power supply board, so I guess its a ground...
At the moment, I'm just trying to get this thing connected to my computer, I'll figure out the command set later, I just need a circuitry nut to tell me if I'm right about ANY of this, or if I'm gonna blow myself up.
Lord Skitch
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actually i traced back to the power board, and pins 1 and 7 connect to the positive power lead on the power board
You need an RS-232 to RS-485/Rs-422 converter. Aten makes a cheap one.
Try this link
http://www.stayonline.com/catalog/connectivitysolutions/signalconverters/7755.asp
I wrote a program for talking to the www.adaptivedisplays.com betabrite and bigdot signs and needed an adapter for that.
Same thing here sounds like. At least you can download the protocol manual for adaptive stuff. If you sift through their manual you might find their pinouts are similar.
Try this link
http://www.stayonline.com/catalog/connectivitysolutions/signalconverters/7755.asp
I wrote a program for talking to the www.adaptivedisplays.com betabrite and bigdot signs and needed an adapter for that.
Same thing here sounds like. At least you can download the protocol manual for adaptive stuff. If you sift through their manual you might find their pinouts are similar.
ASKER
the cable seems to be a simple 3 lead crossover, 2 to 3, 3 to 2, i can make one of those for a few bucks with some parts from radioshack, I just need to be sure I'm connecting the right stuff together, so I dont damage either the computer or the sign...
and as for the protocol, Symon says their protocol is propriatory, but the protocol stuff you linked to will no doubt be a step forward in writing software for this one, thanks!
and as for the protocol, Symon says their protocol is propriatory, but the protocol stuff you linked to will no doubt be a step forward in writing software for this one, thanks!
I don't think you need a 422 to 232 converter. I think the circuit in this box does that already. I expect that the manufacturer had the idea that the computer would connect to this box through RS232 and the same signalling would be sent down the line to other signs through the RS422 interface.
Don't worry about blowing up anything with your serial port.
The difference between the DTE and DCE ports already takes care of the crossover. If the port is as described, then a standard cable will work. (A standard cable has straight through connections.) If a standard cable doesn't work, then you need a null modem cable which does the crossover to allow you to connect DTE to DTE (i.e., computer to computer). Nothing bad will happen if you accidently use a null modem cable in this case, though. It simply won't work.
Also, be aware that the interface may need some of the flow control signals to be asserted, so if you make your own cable, make sure you hook those lines up and can control them in software.
Oh, and a "wall-wart" is one of those transformers that you plug directly into the wall. It sits there on the wall like a wart (and covers up your other outlets). It's the thing that you use to recharge your cell phone or power your external (cable/DSL) modem or power your speakers.
Bradley
Don't worry about blowing up anything with your serial port.
The difference between the DTE and DCE ports already takes care of the crossover. If the port is as described, then a standard cable will work. (A standard cable has straight through connections.) If a standard cable doesn't work, then you need a null modem cable which does the crossover to allow you to connect DTE to DTE (i.e., computer to computer). Nothing bad will happen if you accidently use a null modem cable in this case, though. It simply won't work.
Also, be aware that the interface may need some of the flow control signals to be asserted, so if you make your own cable, make sure you hook those lines up and can control them in software.
Oh, and a "wall-wart" is one of those transformers that you plug directly into the wall. It sits there on the wall like a wart (and covers up your other outlets). It's the thing that you use to recharge your cell phone or power your external (cable/DSL) modem or power your speakers.
Bradley
ASKER
At the moment, I'm gonna get an old POS laptop for ~$50 that I can stick win2k on, so I have easier access to the ports, but as far as the cable goes, I'm gonna solder some pin connectors and some pins to some wires, and slide them into/onto the pins theyre sposda go, that way the ... "cable"... will cost me about 5 cents, and I dont go spending $300 on cables... after I get something that works and such, I can go about actually making a cable, I just dont wanna be at radioshack every day blowing money on cables and crap that i'll never use again hehe
and about these flow control signals... what exactly are you talking about? lol i've never programmed anything for the serial ports, this was sort of a project to force myself to learn how to do some of this stuff, ive learned quite a lot already actually, but i've still got a long ways to go...
hah, "wall-warts"... i like that, and i think im gonna use it! =)
and about these flow control signals... what exactly are you talking about? lol i've never programmed anything for the serial ports, this was sort of a project to force myself to learn how to do some of this stuff, ive learned quite a lot already actually, but i've still got a long ways to go...
hah, "wall-warts"... i like that, and i think im gonna use it! =)
Hmm, I've always found a serial cable to a useful thing; not to say that I haven't had to solder up my own cable or connectors from time to time. I also don't see you spending $300 on a cable. :) You don't need the gold plated, oxygen free copper, extra shielded, with new and improved pixie dust cables.
Thinking about this again, you probably won't have any problems with flow control. Just make sure that you turn it off in the software that you use. You want "no flowcontrol" or "XON/XOFF flow control" and NOT "hardware flow control". Google for RS232 flow control for more information. This is assuming that the other pins on the DB25 connector are not attached to anything...
Serial ports are always easy to access. The trouble comes in when you have to access the parallel port. In Windows 2000 (and above) the parallel port is "protected" by the OS and you need a driver to gain access. If you are going to be using a terminal program, I would not recommend HyperTerm. TeraTerm is a much better program. Be aware that this might be really difficult if you have no idea what the protocol is. The sign may not respond at all if it doesn't get a full frame of data, for example. Hopefully, you'll connect this up and find a nice friendly interface waiting for you. :)
See, wall-wart is the only name I know for it. The other name is transformer-with-molded-in
Bradley (who has his own eBay LED sign that has been collecting dust for a year)
Thinking about this again, you probably won't have any problems with flow control. Just make sure that you turn it off in the software that you use. You want "no flowcontrol" or "XON/XOFF flow control" and NOT "hardware flow control". Google for RS232 flow control for more information. This is assuming that the other pins on the DB25 connector are not attached to anything...
Serial ports are always easy to access. The trouble comes in when you have to access the parallel port. In Windows 2000 (and above) the parallel port is "protected" by the OS and you need a driver to gain access. If you are going to be using a terminal program, I would not recommend HyperTerm. TeraTerm is a much better program. Be aware that this might be really difficult if you have no idea what the protocol is. The sign may not respond at all if it doesn't get a full frame of data, for example. Hopefully, you'll connect this up and find a nice friendly interface waiting for you. :)
See, wall-wart is the only name I know for it. The other name is transformer-with-molded-in
Bradley (who has his own eBay LED sign that has been collecting dust for a year)
ASKER
hehe yeah, ive had to make cables for like... hooking my TI-83 up to my computer, instead of paying TI $50 for it, but i was talkin about spending $300 on 50 different cables, and having none of them work...
I've got some DLLs to control the parallel port, but im gonna use a serial port to try and communicate... and im gonna program all this in visual basic, unless i find its easier to do it in a dos-based format, then ill put dos5 and a C++ compiler on the laptop and use that instead...
for the most part, im gonna brute force the protocol out, it may take forever, but itll eventually get done...
and what kinda sign do you have? =)
skitchy
I've got some DLLs to control the parallel port, but im gonna use a serial port to try and communicate... and im gonna program all this in visual basic, unless i find its easier to do it in a dos-based format, then ill put dos5 and a C++ compiler on the laptop and use that instead...
for the most part, im gonna brute force the protocol out, it may take forever, but itll eventually get done...
and what kinda sign do you have? =)
skitchy
Visual Basic would be my suggestion. The MSComm Control is simple to use, but doesn't really give you feedback. Starting out with a terminal program (TeraTerm) would be your best bet, IMO. This will allow you to find out whether it is an ascii protocol.
Mine is a Texas Digital Systems. It has an RS422 RJ45 connector on the back. I've plugged it in and it passes the power-on self-test, but I've not yet tried communicating with it. I emailed the company for a manual awhile back, but they didn't reply and I didn't follow up. It's on my list, though.
Good luck
Bradley
Mine is a Texas Digital Systems. It has an RS422 RJ45 connector on the back. I've plugged it in and it passes the power-on self-test, but I've not yet tried communicating with it. I emailed the company for a manual awhile back, but they didn't reply and I didn't follow up. It's on my list, though.
Good luck
Bradley
ASKER
ive got no idea how to use any terminal programs... i used to use vterm to hook into a computer at nasa and download pictures my dad uploaded for me, but that was via a modem, and the commands were like... DIAL ###-###-#### and +++ATH and such, and at the moment, im playing with MSComm with my UPS serial interface, tryin to get some data flow to happen there...
skitchy
skitchy
Terminal programs simply provide an ASCII interface to the serial port. If you have a modem on the other end, the modem understands the Hayes (AT) command set, where the command start with AT (for attention). (ATDT<number> to call out; ATH to hangup) If you have a router or DSL modem's management port on the other end, you configure the device through whatever interface the manufacturer has provided.
I suggest using a terminal program first to see if the interface is going to be simple (which is unlikely, but maybe!). You might find a command prompt on the other end when you start up the terminal program and hit enter a couple times. If you don't get a command prompt, you might get some garbage that is going to indicate what sort of packet the sign is sending back. I've not looked into what the "common" LED sign interface protocols are. I doubt there is any sort of industry standard. I'm sure they demand you use their own program(s) to use the sign.
Remember that you also have Baud rate, data bits, parity bits, stop bits to configure. You might try starting with 9600 Baud, 8 data bits, No parity, and 1 stop bit. The Baud rate could be just about anything, but the last three settings are the most common and are often listed as: 8-N-1.
It would probably be very useful if you could find a copy (even demo) of the software designed to control the sign. From there you could get at least an idea of what is happening over the link.
Bradley
I suggest using a terminal program first to see if the interface is going to be simple (which is unlikely, but maybe!). You might find a command prompt on the other end when you start up the terminal program and hit enter a couple times. If you don't get a command prompt, you might get some garbage that is going to indicate what sort of packet the sign is sending back. I've not looked into what the "common" LED sign interface protocols are. I doubt there is any sort of industry standard. I'm sure they demand you use their own program(s) to use the sign.
Remember that you also have Baud rate, data bits, parity bits, stop bits to configure. You might try starting with 9600 Baud, 8 data bits, No parity, and 1 stop bit. The Baud rate could be just about anything, but the last three settings are the most common and are often listed as: 8-N-1.
It would probably be very useful if you could find a copy (even demo) of the software designed to control the sign. From there you could get at least an idea of what is happening over the link.
Bradley
ASKER
Ack lol forgot I left this open, and I'm about to actually start programming for it, so I guess the hardware portion of the program is complete! Thanks!
LordSkitch,
How far did you get with the programming and commands? I have 3 Symon SDU LED signs and I also have the connection documentation from Symon... it's a PDF. I'm in the same boat as you... no software and no clue of how to communicate with the signs... I can send you the PDF via e-mail if you like.
How far did you get with the programming and commands? I have 3 Symon SDU LED signs and I also have the connection documentation from Symon... it's a PDF. I'm in the same boat as you... no software and no clue of how to communicate with the signs... I can send you the PDF via e-mail if you like.
ASKER
I got an RS232 cable and a null modem adapter, but I never got the thing to actually communicate, a guy emailed me sayin...
serial number <SOH> abcdef <STX> ghijkl <ETX> etc etc <EOT>
$01, $02, $03, $04
And can get the sign to make error messages at least.. (sent at 1200baud)
but I cant even get it to do that... so.. I dunno
serial number <SOH> abcdef <STX> ghijkl <ETX> etc etc <EOT>
$01, $02, $03, $04
And can get the sign to make error messages at least.. (sent at 1200baud)
but I cant even get it to do that... so.. I dunno
well that seems like a clue to this thing... I'm guessing that's the format of how to send info to these signs... Do you have that guy's e-mail address? I'd like to pick his brains? Do you have an e-mail address that I could send the connection info too?
ASKER
EE doesnt like people putting email addresses in the posts, so youll have to get this quickly, skitch @ the-coming . com lol lets see if they detect that.
Skitch,
Any progress... I haven't heard from you since I sent you the PDF.
Any progress... I haven't heard from you since I sent you the PDF.
ASKER
I've been sifting through more information, still no joy as of yet
ASKER
the communication board connects to a 9 port plug, that connects to the back of the LED sign, which i imagine has all of the actual control proms and such, i havent taken the sign apart... im not that far yet, im just tryin to get this thing connected to my computer lol
the voltage regulator is a... LM340T-5, a 5v regulator, i .. have no idea what a wall wart is lol but theres a fat tall yellow chip labled DS4E-S-DV9V some sort of 9v relay 4 Form C amber sealed, 200 mW nominal operating power
and as for the connection between pins 1 and 7, here goes some ascii art... lets hope it doesnt mess up too much
|
______|
| |
ooooooooooooo
ooooooooooo
that connects through pin 6 on the line driver, and through to the voltage regulator, and also splits off to a capacitor, and then down to pin 5 on the line driver...
maybe i should be spending my time tryin to get my scanner to work so i can take pictures of this thing...