Hello.

some time ago I got some discared 2x16 LED displays and they use RS485 for the communication. Because I couldn't find any documentation about it, I wonder if is there any standard or maybe just unwritten rules for the commands used to write some text, move cursor etc. that are common from different types and manufacturers?

I will also try to get in touch with the company that made them (long ago) if they will be willing to give me the data if they even still have it.

Thanks for help in advance.

Have a nice day,

Primož

 

Why do you think that they use RS485? There should be no difference in the programming if the protocol is the same.

Which compiler are you using? Which programming language? Which IDE or do you have a test board?

 

Why do you think that they use RS485? There should be no difference in the programming if the protocol is the same.

Which compiler are you using? Which programming language? Which IDE or do you have a test board?

I'm sure it uses RS485, because this are ready to use display for public informations etc.

 

It can be "RS232", "RS 422" or the diviations of "RS". If you are certain, the displays are not actually programmed, they just receive the formatted signal from the MCU and its the MCU that gives them what to display. You can check any display programs for "RS485" with any MCU (not Arduino please).

 

There are no rules for the communication for this manufactured device.

These displays have a serial interface so that a number of them can be driven from a single serial communications link.

I guess the communication will be in ASCII characters. Because all the displays will receive the same data, there will have to be an address data before the character data to be displayed. Of course, you not only do not know the protocol but you do not know the data date (baud rate) either.

Does the display have DIP switches or any other way of setting the address? If there is you could try DMX - address byte followed by a character byte. Otherwise, remove the micro-controller and replace with one programmed yourself.

 

It can be "RS232", "RS 422" or the diviations of "RS". If you are certain, the displays are not actually programmed, they just receive the formatted signal from the MCU and its the MCU that gives them what to display. You can check any display programs for "RS485" with any MCU (not Arduino please).

I'm sure that it uses RS485, because it's written near the connector. I'm going to try with USB to RS485 converter because I'm far more experienced in programing PC applications, also there are many programs out there for sending over serial communications.

There are no rules for the communication for this manufactured device.

These displays have a serial interface so that a number of them can be driven from a single serial communications link.

I guess the communication will be in ASCII characters. Because all the displays will receive the same data, there will have to be an address data before the character data to be displayed. Of course, you not only do not know the protocol but you do not know the data date (baud rate) either.

Does the display have DIP switches or any other way of setting the address? If there is you could try DMX - address byte followed by a character byte. Otherwise, remove the micro-controller and replace with one programmed yourself.

That's all the information I needed. I was just thinking that maybe there is some kind of a "standard" for communication with that displays, but apparently not.

I will try to contact the manufacturer.

Thank you very much for the help.

 

You still need to connect the display properly and RS485 normally has 2 transmission lines, since its a full duplex interface.

 

You still need to connect the display properly and RS485 normally has 2 transmission lines, since its a full duplex interface.

Yes that's true. It has a standar DB9 connector so that shouldn't be a problem.