Arduino MEGA connect with mini thermal receipt printer

Projects Programming
1

Hi everyone,
I use Uno to connect some sensors (like pressure sensor) and then transfer the data to MEGA via I2C.
Subsequently, I would like to implement mini thermal receipt printer to print out the data on sheets.

The link below is the information about the currently used printer

However, I have difficulties getting it right.
If it is written as printer.println(c);
MEGA can not read the data transferred from Uno, and printer only print the first character.
(ex. "P" out of "Pressure")
If printer.println(c); is removed, MEGA is able to read the data.
The printer should be fine because the printer prints "start" according to the script printer.println("start");

void receiveEvent(int howMany)
{
  while (Wire.available())
  {
    // receive one byte from Master
    incomingByte = Wire.read();
    Serial.write(incomingByte);
    Serial.println(incomingByte);
  }
}

.

salve_read.ino (1.2 KB)