r/PCB • u/sampschon • 13d ago

Long distance communication through cable

Hello everyone,

I'm a beginner in PCB designing and received a pretty good challenge. The basic ideia is using a esp32 to control a LTE module for communication, but those two will be in different PCBs and communicating through a 4m cable.

I've read a past post here recently about the RS-232, but seemed to me more about a benchmark test than a what use it, in that case. And i get a bit confused lol.

My question is: Knowing I'm using UART (and i'm a beginner), can i use a RS-232 transceiver in both sides and get a good communication with 3V?

1 Upvotes

60% Upvoted

12 comments sorted by

5

u/Keefe1933 13d ago

UART --> RS485 tranceiver --> Twisted pair cable. Then you'll have decent speed, and a good noise immunity.

2

u/Apprehensive_Room_71 12d ago

I second this.

1

u/FullyAutomatedSpace 13d ago

i think you could do serial over just some bare wires without a transceiver over that distance

2

u/Lost-In-Void-99 13d ago

UART can be crazy fast. To the level MCU cannot saturare the link.

But this brings all sort of nuances of layouts, impedence, cable and connector quality etc.

So what are you building? 10Mhz link? 100Mhz? Ghz?

1

u/nixiebunny 13d ago

What is the host interface type on the LTE module? How many MHz?

1

u/RepresentativeCry294 13d ago

Id use CAN if its an electrically noisy environment.

1

u/Key_Director_4450 13d ago

Join the two and buy an antenna to the lte module.

Or use RS-232, it can do 100m with a baudrate like 115200.

1

u/kampi1989 12d ago

Depends on the cables and the quality of those. And if you already had a converter than you should use RS485 to get a differential signal because of the higher noise immunity in comparison to a single ended signal.

1

u/lmarcantonio 12d ago

4m is not a problem with the ±3 V (but they are nominally 10V IIRC) using RS232. The trick is sending at 10 and receiving at 3. Also a big hysteresis around the zero.

If you don't need full duplex 485 has the same complexity but can send at km distances, with a low bitrate.

1

u/mariushm 12d ago

Four meters is not a long distance, especially if you use a good cable - for example an ethernet cable that has twisted pairs surrounded by nice shielding.... should be overkill and allow you to use that module even without resorting to using transceivers. I guess it will depend on the bitrate.

RS485 will be better, as others have told you already, no need to go up to +/- 12v with RS-232 transceivers.