I have no idea how far uart can transmit signal or haw far it can receive signal.

if ATmega328p sending byte via uart protocol with RS232 interface

How far can signal generated by ATmega328p be sent 10 meters, 50 meters, 1 KM, more than 1KM

 

According to TI, for ordinary RS232 you have:

19200	50 ft
9600	500 ft
4800	1000 ft
2400	3000 ft

But there are many factors that influence distance and it is generally much better practice to use something like RS485 for long distances. Long runs connected directly to the processor will be very vulnerable to noise from external signals.

What are you trying to do?

 

I have no idea how far uart can transmit signal or haw far it can receive signal.

if ATmega328p sending byte via uart protocol with RS232 interface

How far can signal generated by ATmega328p be sent 10 meters, 50 meters, 1 KM, more than 1KM

In ribbon cable, twisted pair, coax, fiber optic?

 

Depending on what you consider allowable, there is no practical limit. If you mean on a single wire or a twisted pair, then the numbers provided by @Yaakov are reasonable estimates. If you connect the UART to RS-485 transceivers then the distance will be longer.

 

What are you trying to do?

I had this doubt that had to be cleared. I've never seen a cable longer than 10 feet used before. I used a cable about 10 feet long to send data from AVR to PC via UART.

According to you, when the baud rate is 9600, then Uart can transmit data up to 50 feet.

I'm not sure but I think transmission distance also depends on the type of interface. If the AVR is configured for 9600 and the interface is TTL. Approximately how far can an AVR transmit a signal?

 

Another factor that no one mentions is when I use a micro the max232 RS232 IC or equivalent is supposed to generate +10v ~ -10v.. The ideal is +12v ~ -12v.. However, the micro sitting at 5v or 3v barely makes 8 / 9v. so a swing of +8v ~ -8v isn't as good as it gets.... RS485 or CanBus is far superior to send 50 foot..

 

RS232 uses -12V and +12V or more. TTL will not get you the same distance.

Bb

 

TTL will get you 18-36" on a good day.

 

If you use RS232 and a high quality cable such as Belden 9891, you will just have sufficient conductors and operate at considerable distance with 12v /9v RS232.

 

I have a board I am coding for and it uses a UART to a serial to USB board. Ive been ruining at 115200 baud reliably using a 6 in jumper. I couldn’t find the one with the right end so I hooked two together. No go.

Bob

 

Do you really want RS232? It's more complicated than you probably need, and RS422 or RS485 has a much longer range. That's RS422 if you want 2-way communication without worrying about messages going one way colliding with messages the other way. RS485 would be half-duplex, i.e. the same pair of wires carries communication both ways, so you have to think about who's controlling the channel at any given time.