MAX3232 RS232 to TTL Serial Converter Module

// MAX3232 RS232 to TTL Serial Converter Module
// Arduino Uno example: simple serial bridge using SoftwareSerial.
// 
// Wiring used:
// Arduino D2 <- module TXD
// Arduino D3 -> module RXD
// 5V -> VCC, GND -> GND

#include <SoftwareSerial.h>

static const uint8_t MAX3232_RX_PIN = 2; // Arduino receives on this pin (connect to module TXD)
static const uint8_t MAX3232_TX_PIN = 3; // Arduino transmits on this pin (connect to module RXD)

SoftwareSerial max3232Serial(MAX3232_RX_PIN, MAX3232_TX_PIN);

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ;
  }

  max3232Serial.begin(9600);

  Serial.println("MAX3232 TTL serial example");
  Serial.println("Type in the Serial Monitor and press Enter.");
  Serial.println("Text will be sent to the module RXD pin and echoed back from TXD if the external RS232 device replies.");
}

void loop() {
  // Forward data from the USB serial monitor to the MAX3232 module.
  while (Serial.available() > 0) {
    char c = (char)Serial.read();
    max3232Serial.write(c);
  }

  // Show any data coming back from the MAX3232 module.
  while (max3232Serial.available() > 0) {
    char c = (char)max3232Serial.read();
    Serial.write(c);
  }
}