HC-12 V3.0 Long-Range 433MHz Wireless Serial Module – 1000m UART Communication, SI4432/SI4463 RF Chip, Bluetooth Alternative

Usage Guide

Hardware Overview

The HC-12 V3.0 module features a compact green PCB design with the RF chip (SI4463 or SI4438) and an onboard MCU. The module includes a spring antenna (included) and a SET pin for entering configuration mode .

Key Components:

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

• Onboard MCU (8051 or N32S032 ARM Cortex-M0) – Handles UART communication and AT command processing

• Spring Antenna – Included for optimal range; must be soldered to the ANT pad

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

Pinout Description

Wiring Instructions

Basic Connection (Microcontroller to HC-12):

Important Connection Notes:

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

• The SET pin is internally pulled high. Leave it floating (disconnected) for normal operation. Pull it LOW (connect to GND) to enter AT command mode .

Antenna Connection:

• The module includes a spring antenna that should be soldered to the ANT pad for optimal performance .

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

• A simple 17-23cm straight copper wire can also be used as an antenna .

Operating Modes (FU1-FU4)

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

Mode Characteristics:

• FU1: Supports 8 serial baud rates (1200-115200bps). Idle current ~3.6mA. Best for balanced power and performance .

• FU2: Only supports 1200, 2400, and 4800bps serial baud rates. Idle current ~80µA. Perfect for battery-powered sensors .

• FU3 (Factory Default): Automatically adjusts the wireless transmission air baud rate according to the serial port baud rate. Offers the best overall performance .

• FU4: Serial baud rate fixed at 1200bps, air baud rate 500bps for maximum sensitivity and range (up to 1000m) .

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 SET pin LOW (connect to GND). 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 approximately 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 003: 434.2 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
}

Default Factory Settings

Range Optimization Tips

• Use a proper antenna – Solder the included spring antenna to the ANT pad or use a 17-23cm straight wire

• Use FU4 mode for maximum range – FU4 mode with 1200bps serial baud rate provides the longest distance

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

• 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 1-2 meters) can overload the receiver; start with 5-10 meters distance during testing

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 V3.0 is backward compatible with earlier versions (V2.x) of the HC-12, but some users have reported compatibility issues between V3.0 and older modules when using certain AT commands . It is recommended to use modules from the same production batch or test thoroughly when mixing versions.