HC-12 V2.6 433MHz Long-Range Wireless Serial Module – 1000m UART Communication, SI4438/SI4463 RF Chip, Bluetooth Alternative

Usage Guide

Hardware Overview

The HC-12 module features a compact design with the SI4438 (or SI4463) RF chip and an onboard MCU. The module includes a spring antenna (included) and a SET pin for entering configuration mode.

Key Components:

• SI4438/SI4463 RF Chip – High-performance FSK transceiver

• Onboard MCU – Handles UART communication and AT command processing

• Spring Antenna – Included for optimal range

• SET Pin – Used to enter AT command mode for configuration

Pinout Description

Wiring Instructions

Basic Connection (Microcontroller to HC-12):

Important: When connecting two HC-12 modules to communicate with each other, you do not need to cross the connections. Simply connect each module’s TXD to its own microcontroller’s RX pin, and RXD to TX pin.

Antenna Connection:

• The module includes a spring antenna that should be soldered to the ANT pad

• For maximum range, ensure the antenna is straight and away from metal surfaces

Voltage Note: If the module needs to work in transmission mode for extended periods and the supply voltage exceeds 4.5V, it is recommended to add a 1N4007 diode in series to prevent the built-in LDO from overheating .

Operating Modes (FU1-FU4)

The HC-12 offers four operating modes that allow you to optimize for power consumption or performance :

Mode Characteristics:

• FU1: 8 serial baud rates (1200-115200bps) supported. The idle current is about 3.6mA .

• FU2: Only supports 1200bps, 2400bps, and 4800bps serial baud rates. The idle current is about 80µA .

• FU3 (Factory Default): Serial baud rate: 9600bps. The module automatically adjusts the wireless transmission air baud rate according to the serial port baud rate .

• FU4: Serial baud rate fixed at 1200bps, air baud rate 500bps for maximum sensitivity and range .

AT Command Configuration

Entering AT Command Mode:

There are two methods to enter AT command mode :

1. Method 1 (Normal operation): While the module is powered normally, pull the 5th pin “SET” LOW. The module enters command mode. Release SET to exit.

2. Method 2 (Power-on): Pull SET LOW before applying power, then power on the module. After 1 second, the module enters command mode.

Important Notes for AT Commands:

• In command mode, the UART format is fixed at 9600 bps, 8 data bits, no parity, 1 stop bit

• Commands must be sent in uppercase

• Each command must be terminated with \r\n (carriage return + line feed)

• Send commands quickly – the module has a short timeout between characters

Available AT Commands :

Supported Baud Rates: 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200 bps

Channel Frequency Mapping:

• Channel 001: 433.4 MHz

• Channel 002: 433.8 MHz

• …

• Channel 100: 473.0 MHz

Transmit Power Levels (AT+Px) :

Arduino Example Code

Basic Serial Passthrough (Transparent Mode):

// HC-12 Wireless Serial Communication
// Module connected to SoftwareSerial to leave hardware Serial for debugging

#include <SoftwareSerial.h>

SoftwareSerial hc12(10, 11);  // RX = pin 10 (to HC-12 TX), TX = pin 11 (to HC-12 RX)

void setup() {
  Serial.begin(9600);     // Debug serial to PC
  hc12.begin(9600);       // HC-12 baud rate (must match module setting)
  
  Serial.println("HC-12 Wireless Serial Ready");
}

void loop() {
  // Forward data from PC Serial to HC-12 (wireless transmission)
  if (Serial.available()) {
    hc12.write(Serial.read());
  }
  
  // Forward data from HC-12 (wireless reception) to PC Serial
  if (hc12.available()) {
    Serial.write(hc12.read());
  }
}

Sending AT Commands to Configure HC-12:

// Send AT commands to configure HC-12 module

#include <SoftwareSerial.h>

SoftwareSerial hc12(10, 11);  // RX = pin 10, TX = pin 11

void setup() {
  Serial.begin(9600);
  hc12.begin(9600);
  
  // Pull SET pin LOW to enter command mode
  pinMode(9, OUTPUT);
  digitalWrite(9, LOW);   // SET pin LOW
  
  delay(100);  // Wait for module to enter command mode
  
  // Send AT commands
  hc12.println("AT");      // Test command
  delay(500);
  hc12.println("AT+V");    // Get version
  delay(500);
  hc12.println("AT+RX");   // Get all parameters
  
  delay(1000);
  
  // Read responses
  while (hc12.available()) {
    Serial.write(hc12.read());
  }
  
  // Exit command mode by releasing SET pin
  digitalWrite(9, HIGH);
}

void loop() {
  // Nothing here
}

Range Optimization Tips

• Use FU3 or FU4 mode – FU3 provides the best overall performance; FU4 offers maximum range at lower data rates

• Set maximum transmit power – Use AT+P8 for +20dBm (100mW) output

• Use a proper antenna – The included spring antenna is tuned for 433MHz; ensure it is straight and elevated

• Lower the baud rate – Slower data rates improve receiver sensitivity; use 1200-4800bps for maximum range

• Maintain line of sight – For 1000m range, clear line of sight is required

• Avoid metal obstacles – Metal structures and reinforced concrete significantly reduce signal strength

• Stable power supply – The module draws up to 100mA when transmitting; ensure your power supply can handle this

• Keep modules separated – Direct proximity (less than 1 meter) can overload the receiver

Default Factory Settings

Important Compatibility Note

HC-12 cannot communicate with HC-11 modules . These modules use different protocols and are not interoperable. For wireless communication, all modules in your network must be HC-12 modules. The HC-12 V2.6 is backward compatible with earlier versions of the HC-12, ensuring seamless integration with existing deployments .