Microcontrollers Communication

Exercise #7: Serial communication

Start by creating a new project (e.g. clone this repository, open it in the Particle ID, and use the Start new project button to turn it into a project).

Setup the circuit

Connect the RS232 circuit to your microcontroller VIN, GND, TX, RX. Connect the two DB9 plugs with a DB9 cable.

Add the code

• modify your program as follows:

• outside of your setup and loop functions:

  // combined message
  String temp_message = "";
  
  // tx is transmitter, rx is receiver
  void mirror_serial(Stream &tx, Stream &rx) {
    while (tx.available()) {
      byte c = tx.read();
  
      if (c == 0) {
        // do nothing when 0 character encountered
      } else if (c >= 32 && c <= 126) {
        // regular ASCII range
        temp_message += (char) c;
        tx.print((char) c); // bounce back to transmitter
        rx.print((char) c);
      } else  if (c == 13) {
        // return character received
        tx.println(); // bounce back to transmitter
        rx.println();
        rx.print("Whole line: ");
        rx.println(temp_message);
        temp_message = "";
      } else {
        // unknown character (127=backspace, 27=esc, etc.)
        rx.println();
        rx.print("Unknown int: ");
        rx.println(c);
      }
    }
  }

• in the setup function:

  Serial.begin(9600);
  Serial1.begin(19200, SERIAL_8N1);
  Serial.println("Started up");

• in the loop function:

  mirror_serial(Serial, Serial1);
  mirror_serial(Serial1, Serial);

• compile & flash the new program
• start your serial monitor with the Show Serial Monitor button in the Particle IDE and hit Connect

• start typing in the serial monitor to send messages