Communication under 15m ?

[SphinX]

Hi,

I am designinig a main unit attach to terminal units.

I use RS485 protocol between the main units becuse the distance is long (about 50 meter)

I plan to communicate between the main unit and the terminal.
The distance between the Main unit and Terminal units under 15 meter .

Without any protocols like RS484 or RS232, Can i sendnormal data beteween them.

Is that work ?

In other word what is the maximum distance that can two microcontroller communicate together without need any RS-xxx protocols.

Thanx

 

[mrcube_ns]

I use simple serial cable (Rx, Tx, gnd and sheeld) to 30 meters without any error protection protocol a few times and I never have problem.

So od 15 meters you dont need 422 or 485 its for longer distances.


Mr.Cube

 

[Igor_S]

hi,

It mostly deends on many enviromental factors - how noisy your enviroment is, driver rise/fall time causing reflections on unterminated (if) lines, the data transfer speed etc. The differential protocols (RS422/485) are intended to eliminate common-mode noise from enarby sources.
Thus, if encounter problems, you should try:
1) series termination resistors, plased near driver's output - does make sense on UNIDIRECTIONAL lines. Something about 50 ohm value.
2) Decreasing the speed of data transfer
3) May be, consider additional shielding of communication cabling

 

[tlp71@hotmail.com]

if you need transmit in TTL or LVTTL i think that is not a good pratice, first if you use a standard (rs232,rs485,lvds or similar) you can interface you device also uf you need to change some devices whit differnt VCC and many others cots devices.
If you don't need speed faster i think that 485 is better also for short distances, in fact you can make a comunication whit better quality.
Bye

 

[SphinX]

Hi,

Please i ask for transmitting TTL\CMOS digial data over wire cable to max. 15 meter.
Is there any problems?

I will attach the main unit with 12 terminal and i don't want to make RS232 or RS485 converter for each terminal.

Thanx for the replies.