[ARM] Long 1-wire link (10m ... 30m)

[memarian]

Hello guys,


I'm designing a board for communication between 2 instruments (and doing some other stuff) with these specs :

Wire length : Between 10m ... 30m (depends on the installation environment)

Available wire/cable type : 2 wires of a simple 4x1 or 4x1.5 cable. These aren't twisted pair.The cable is currently installed and the i can't change it or install anything else.

Baud Rate : Minimum 2400bps half-duplex or 1200bps full duplex(but i prefer 9600bps half duplex).


I wanted to use RS485, but i can't (There isn't any available twisted-pair).

On both ends there will be a MCU (Currently is STM32F103) and power will be available , so there won't be any shortage in power.

I'm currently thinking about using 1-wire link with drivers like DS2480B.

Is there anything that i'm missing? any other recommendation?

BTW : on the other 2 conductors of our cable there will a AC 40V-2..4A Power supply that will be rectified
and used for driving a dc motor at one end of the cable.

Thanks.

 

[horace1]

I would have thought that at 9600bps RS232 would be suitable for a distance of 10 to 30 metres so long as there is not too much electrical noise in the environment

 

[memarian]

I would have thought that at 9600bps RS232 would be suitable for a distance of 10 to 30 metres so long as there is not too much electrical noise in the environment

Hi,

I only have 2 wires available for this link and RS232 needs 3. (this link is a 2 way link not 1 way)

About the environment noise: the environment noise varies with every installation ,and also the power supply of a motor is on other 2 conductors of the cable.

 

[horace1]

Hi,

I only have 2 wires available for this link and RS232 needs 3. (this link is a 2 way link not 1 way)

About the environment noise: the environment noise varies with every installation ,and also the power supply of a motor is on other 2 conductors of the cable.

you could OR the TX and RX onto two wires to give you half duplex communication using a master/slave protocol

there was a post on the microchip forum discussing this
https://www.microchip.com/forums/m500934.aspx

 

[FvM]

You can e.g. use the LIN bus standard. Or any self-designed wired-OR/wired-NAND bus.

 

[D.A.(Tony)Stewart]

If noise exists on grounds a large CM choke is necessary and of course ESD protection.

 

[memarian]

It seems that LIN BUS is suitable for my project and transceiver chips are easily available & cheap!

I will study more about LIN BUS and see what happens.

 

[ard]

I would go with a variation of Horace's suggestion. In fact, I have done this successfully, and its been working fine for months.

You'll find more on this page: https://www.picbasic.co.uk/forum/showthread.php?t=17282&page=2

Regards,

Anand

 

[D.A.(Tony)Stewart]

i used to run 10m RS232 cables in the lab easily to one monitor using diode OR and 10k to a status pin at V- to an RS 232 dumb terminal to watch communication in both directions at 9600 in the 70's with no problem, but 6 port MuX boxes to printers would occasional have errors in the office from ground noise , easily fixed as I replied earlier.