Connect to Arduino Mega 2560 using comm UART with device CH431A

Development Tools IDE 1.x
1

Question: Is possible to connect to arduino mega 2560 or EPS8266 relay using communication UART with device CH431a ( link to device: https://aliexpress.com/item/4000052560354.html ) ?

Schema:

1000×1000 191 KB

Code compiled to Mega 2560 using cable USB (not over CH431a):

char mystr[5] = "Hello"; //String data


void setup() {
  // Begin the Serial at 9600 Baud
  Serial.begin(9600);
}


void loop() {
  Serial.write(mystr,5); //Write the serial data
  delay(1000);
}

Compiler successes.

Using USB Programmer CH431a I am getting

???? ???? ????

at braud 9600. Can you help me why it is that I still have unknown signs.