HC-12

// HC-12 on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/hc-12
// HC-12 on an Arduino Uno: TXD -> D2, RXD <- D3, SET <- D4
// Prints the module's settings, then forwards Serial Monitor text over the air and back.
#include <SoftwareSerial.h>

SoftwareSerial hc12(2, 3); // RX, TX
const int SET_PIN = 4;

void enterCommandMode() {
  pinMode(SET_PIN, OUTPUT);
  digitalWrite(SET_PIN, LOW);
  delay(100);
}

void leaveCommandMode() {
  pinMode(SET_PIN, INPUT); // released: the module's own pull-up takes SET high
  delay(100);
}

void setup() {
  Serial.begin(115200);
  hc12.begin(9600); // factory baud rate
  enterCommandMode();
  hc12.print("AT+RX"); // report mode, baud, channel and power
  delay(300);
  while (hc12.available()) Serial.write(hc12.read());
  leaveCommandMode();
  Serial.println(F("HC-12 ready: type to send"));
}

void loop() {
  while (Serial.available()) hc12.write(Serial.read());
  while (hc12.available()) Serial.write(hc12.read());
}

// HC-12 on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/hc-12
// HC-12 on an ESP32 DevKit V1 (module powered from 3V3): TXD -> GPIO16, RXD <- GPIO17, SET <- GPIO4
// Prints the module's settings, then forwards Serial Monitor text over the air and back.
#include <Arduino.h>

const int HC12_RX = 16; // ESP32 receives here
const int HC12_TX = 17; // ESP32 transmits here
const int SET_PIN = 4;

void enterCommandMode() {
  pinMode(SET_PIN, OUTPUT);
  digitalWrite(SET_PIN, LOW);
  delay(100);
}

void leaveCommandMode() {
  pinMode(SET_PIN, INPUT); // released: the module's own pull-up takes SET high
  delay(100);
}

void setup() {
  Serial.begin(115200);
  Serial2.begin(9600, SERIAL_8N1, HC12_RX, HC12_TX);
  enterCommandMode();
  Serial2.print("AT+RX");
  delay(300);
  while (Serial2.available()) Serial.write(Serial2.read());
  leaveCommandMode();
  Serial.println("HC-12 ready: type to send");
}

void loop() {
  while (Serial.available()) Serial2.write(Serial.read());
  while (Serial2.available()) Serial.write(Serial2.read());
}

// HC-12 on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/hc-12
// HC-12 on a Raspberry Pi Pico (arduino-pico, module powered from 3V3(OUT)): TXD -> GP1, RXD <- GP0, SET <- GP2
// Prints the module's settings, then forwards Serial Monitor text over the air and back.
#include <Arduino.h>

const int SET_PIN = 2;

void enterCommandMode() {
  pinMode(SET_PIN, OUTPUT);
  digitalWrite(SET_PIN, LOW);
  delay(100);
}

void leaveCommandMode() {
  pinMode(SET_PIN, INPUT); // released: the module's own pull-up takes SET high
  delay(100);
}

void setup() {
  Serial.begin(115200);
  Serial1.setTX(0);
  Serial1.setRX(1);
  Serial1.begin(9600);
  enterCommandMode();
  Serial1.print("AT+RX");
  delay(300);
  while (Serial1.available()) Serial.write(Serial1.read());
  leaveCommandMode();
  Serial.println("HC-12 ready: type to send");
}

void loop() {
  while (Serial.available()) Serial1.write(Serial.read());
  while (Serial1.available()) Serial.write(Serial1.read());
}