Communications Trouble

I am trying to communicate through two, Arduino UNO and Nano. Looks like it is communicating not showing any error code even, but data showing in serial monitor is a set of codes inclusive of some simples like "??!!!A" randomly...

Need help, please !

Need help, please !

That is completely unrealistic since you have shown no schematic and no code.

Have a look at the examples in Serial Input Basics - simple reliable ways to receive data. There is also a parse example to illustrate how to extract numbers from the received text.

The technique in the 3rd example will be the most reliable.

You can send data in a compatible format with code like this

Serial.print('<'); // start marker
Serial.print(value1);
Serial.print(','); // comma separator
Serial.print(value2);
Serial.println('>'); // end marker

If that does not solve your problem please take account of the comments in Reply #1

…R

@OP
How have you connected the UNO and NANO?

1. Using hardware UART Port?
uart-1x.png
Figure-1: UNO and NANO connection using hardware UART Port (UART)

UNO NANO
TX RX
RX TX
GND GND

2. Using software UART Port (SUART)?
uart-2softx.png
Figure-2: UNO and NANO connection using software UART Port (SUART)
UNO NANO
STX (3) SRX (2)
SRX (2) STX (3)
GND GND

3. Using I2C Bus?
i2c-1.png
Figure-3: UNO and NANO connection using I2C Bus
UNO NANO
SDA (A4) SDa (A4)
SCl (A5) SCL (A5)
GND GND

2.2k resistor from SDA pin to 5V
2.2k resistor from SCL line to 5V

4. USing SPI Port?
spi.jpg
Figure-4: UNO and NANO connection using SPI Port
UNO NANO
SS/ (10) D10
MOSI (11) D11
MISO (12) D12
SCK (13) D13
GND GND

5. Have you written some codes? Please post your codes.

uart-1x.png

uart-2softx.png

i2c-1.png

spi.jpg