ask about uart?

Question

how long wire I can use for the uart to uart communication beetween microcontroller, without using RS-232 level converter ?

Answer 1

You can reliably use up to 50feet of cable as long as the maximum capacitance of the cable is less than 2500pf.

using low cap cable and slowing the baud rate will dramatically raise the transmission length. unofficially you could find that you could far exceed the 50ft recommendation. You might find that 100's if not 1000' of feet of cable are possible with a slow enough rate and decent cable. There are no guarantees for these large distances using rs232.

I have had sucessful experience using 4wire rs485 and over 6000 feet of cable to link PLC's. So if you must aboslutely go such distances then consider using rs232/rs485 converters or better still fiberoptic. see blackbox