Hello everyone.

I read about Rs485 today and I am just curious what I would need to design my own bus.

If I would in example like to control five Leds. (I know that this would be much easier with a Microcontroller)

I would then use my PC as the Master. But I don't understand what kind of Hardware I would need for my Leds to make them a slave and to give them a unique adress.

Thanks in advance for any advice,

Best regards,

Michael

 

You need a Modem switch, they used to be LSI IC's before the advent of built in modem function into μp.
You may still be able to obtain a LSI stand alone version, I used to use one made by Analogue Devices, I used it to convert parallel data from a paper tape reader to serial and also back to a back to parallel for a paper punch.
If you want to get fancier with addressable multi-drop stations then you could go to Modbus or one like it.
Max.

 

Hello everyone.

I read about Rs485 today and I am just curious what I would need to design my own bus.

If I would in example like to control five Leds. (I know that this would be much easier with a Microcontroller)

I would then use my PC as the Master. But I don't understand what kind of Hardware I would need for my Leds to make them a slave and to give them a unique adress.

Thanks in advance for any advice,

Best regards,

Michael

RS485 is a serial differential signal standard that allows you to connect multiple transmitters and receivers on the same bus. And although you could use it to receive messages at multiple points (up to 32 in the normal standard, although newer chips allow more nodes than that) only one transmitter can work at any given time.

You cannot just use RS485 stand-alone chips to get what you want. For that, you need one MCU per node (in this case, LED being controlled) capable of discerning whatever protocol you're using to communicate. The most common communication protocol is UART, although you could also use MODBUS, I2C, SPI, Microwire. and several others.
My advice is, learn how to program and use an MCU before you jump into learning how to set up a multi-node communications network.

EDIT: Max, you're more versed in this subject than I am. Please feel free to correct me if I made a mistake or you think that clarification is needed.

 

Thanks to both of you!

So I would use a Microcontroller to translate the Rs485 bus into an appropriate Communication protocol and I would also use the Microcontroller to give the Rs485 receiver an adress?

Best regards,

Michael

 

If you have a multi-drop system, otherwise if only a single stn. then one would not be needed.
Max.

 

Thanks to both of you!

So I would use a Microcontroller to translate the Rs485 bus into an appropriate Communication protocol and I would also use the Microcontroller to give the Rs485 receiver an adress?

Best regards,

Michael

Yes to multidrop, as Max just said. Another way around it would be using digital gates instead of MCU's, but although no programming would be needed, that would probably just complicate things.
This is a good moment for you to start looking into MCU's

 

Thanks again.

Just to be sure that I got it right:

By single you mean if I would just use one Led?
Then I would not have to assign an adress to the LED as there is just one device on the bus.
But a Microcontroller would still be needed for the communication protocol.

Regards,

Michael

 

By single stn I meant a single master and slave rather than a master with multiple slave stations. (drops).
Max.

 

Thanks again.

Just to be sure that I got it right:

By single you mean if I would just use one Led?
Then I would not have to assign an adress to the LED as there is just one device on the bus.
But a Microcontroller would still be needed for the communication protocol.

Regards,

Michael

If you only want to turn one LED on and off, you don't need an MCU. Sure, you could use a RS485 chip in case the "On" button (or signal) is far away from the LED itself. That would indeed make your circuit more reliable.

It would be real helpful if you were to disclose more details of what you have in mind.

 

If you only want to turn one LED on and off, you don't need an MCU. Sure, you could use a RS485 chip in case the "On" button (or signal) is far away from the LED itself. That would indeed make your circuit more reliable.

It would be real helpful if you were to disclose more details of what you have in mind.

It was more a like general question because I read about Rs485.
There isn't any specific project.

Regards,

Michael

 

The total info is still very vague, if you want to use a PC then if it has a P.Port then use the output lines, there must be quite a few V.B. examples etc. out there.
Max.