Summary of 433MHz wireless module configuration
HC-12 are low-cost 433 MHz wireless serial modules (SI4463-based) that form a wireless UART link up to 1800 m line-of-sight. They support 3.2–5.5 V power, 3.3V/5V UART levels, configurable AT commands, 100 frequency channels (433.4–473.0 MHz), up to 20 dBm output, and multiple serial baud rates. Four operation modes (FU1–FU4) trade speed for range; FU4 gives longest range (1800 m) with strict packet limits. Modules must share mode and speed to communicate; configuration is done via AT commands with SET pulled low using a USB-to-serial adapter.
Parts used in the HC-12 Wireless UART Link:
- HC-12 433MHz wireless serial module (based on SI4463)
- External antenna (compatible with HC-12)
- Power supply 3.2V–5.5V
- USB-to-serial converter (example: CP2102)
- Wires/jumper leads for connections
- Microcontroller or UART-capable device (3.3V or 5V)
Description
HC-12 are cheap 433MHz wireless serial port communication modules with a range up to 1800m in open space. Each costs about $5 when bought from China, and 2 of them can create wireless UART link that can be used, for example, to transfer telemetry data from UAV. Or drive IoT device. Or connect sensors. Or whatever else one can think of.
It is based on SI4463 RF chip, has build in microcontroller, can be configured using AT commands and allows to use external antenna. Working frequency is divided into 100 channels starting from 433,4MHz up to 473,0MHz with 400kHz channel separation. Maximum output power is 100mW (20dBm) and receiver sensitivity differs from -117dBm to -100dBm, depending on transmission speed. It accepts 3,2V-5,5V power supply and can be used with 3.3V and 5V UART voltage devices (5V safe).
HC-12 serial port supports following baud rates:
- 1200bps
- 2400bps
- 4800bps
- 9600bps (default)
- 19200bps
- 38400bps
- 57600bps
- 115200bps
Each HC-12 can work in one of following modes:
- FU1 – moderate power saving mode with 250000bps “over the air” baud rate. Serial port baud rate can be set to any supported value
- FU2 – extreme power saving mode with 250000bps “over the air” speed. Serial port rate is limited to 1200bps, 2400bps, 4800bps
- FU3 – default, general purpose mode. “Over the air” speed differs depending on serial port speed. The same goes for maximum range:
- 1200bps ~ 1000m
- 2400bps ~ 1000m
- 4800bps ~ 500m
- 9600bps ~ 500m
- 19200bps ~ 250m
- 38400bps ~ 250m
- 57600bps ~ 100m
- 115200bps ~ 100m
- FU4 (available in version 2.3 or newer) – long range mode. “Over the air” speed is limited to 500bps and serial port speed to 1200bps. Because air speed is lower than port speed, only small packets can be send: max 60 bytes with interval of 2 seconds. In this mode range is increased to 1800m.
Pair of HC-12 that creates a wireless link has to work in the same mode (FU1, FU2, FU3, FU4) and with the same speed.
Configuration
HC-12 can be configured using AT command. The best way to do it, is to use USB-to-serial converter like CP2102. To put HC-12 into AT mode, pull SET pin to GND like this:
For more detail: 433MHz wireless module configuration
- What frequency range do HC-12 modules use?
They operate on 100 channels from 433.4 MHz up to 473.0 MHz with 400 kHz spacing. - How do I configure an HC-12 module?
Use AT commands via a USB-to-serial converter like CP2102 and put HC-12 into AT mode by pulling the SET pin to GND. - Can HC-12 work with 5V UART devices?
Yes, HC-12 accepts 3.3V and 5V UART voltage devices and is 5V safe. - What is the maximum output power and receiver sensitivity?
Maximum output power is 100 mW (20 dBm); receiver sensitivity ranges from -117 dBm to -100 dBm depending on speed. - Which baud rates are supported by the HC-12 serial port?
Supported serial baud rates are 1200, 2400, 4800, 9600 (default), 19200, 38400, 57600, and 115200 bps. - What are the operation modes and how do they affect range?
Modes FU1, FU2, FU3, FU4 trade speed for range; FU4 (long range) limits air speed to 500 bps and increases range to 1800 m with small packet limits. - Do both HC-12 modules need the same mode and speed?
Yes, a pair must work in the same mode (FU1–FU4) and at the same speed to form a link. - What range can I expect at 9600 bps?
At 9600 bps in FU3 mode the approximate range is about 500 m.
