A Full-Fledged 433-473MHz Sender And Receiver With Its Own Microprocessor

The HC-12 goes far beyond the typical garage-door opener RF sender and receiver boards: it is acting more like a professional transceiver, can send and receive (allowing two-way communications), and supports a wide frequency range with channels.

This module can control garage doors and remote-control devices just like the other RF modules described here. It is much more capable, though, and can serve as a programmable data transceiver.


This board uses its own microprocessor that takes care of all receiving and sending tasks. Controlling the board is very easy and does not add any overhead to your own microprocessor.

Frequency Range And Channels

The board can send and receive in a frequency range of 433.4-473.0MHz which is organized in channels with a step size of 400kHz.

Its maximum transmitting power is +20dBm/100mW, and the receiver sensitivity is excellent with -116dBm. In free line of sight, distances of over 1km can be bridged.

Both the wide frequency range and the high RF output power are incompatible with legal reguirements for free use in Europe. It is illegal to use this device without an appropriate license (i.e. radio amateur).


This breakout board by default emits 100mW which is well above the legal limit of 10mW in Europe. The RF power can be reduced by software.

Item Value
Voltage 3.2-5.5V
Frequency 433MHz or 315MHz
Output Power 11dBm / 12.5mW
Sending Modes FU1, FU2, FU3, FU4
Standby Current 3.6mA, 80uA, 16mA, 16mA
Sleep Current 22uA
Operating Current 100mA
Default Mode FU3 at 9600bps, Channel 01 (433.4MHz)
Modulation Mode AM (OOK)
Transmission Rate <10 Kbps
Interface UART 3.3V/5V TTL level
Size 27.4x13.2x4mm

There are two versions of this board available: one with the microcontroller STM8S003F3U6, and one with the STM8S003F3P6. These microcontrollers are identical. They differ solely in package size.



On the one side, the board features a through-hole connector and an IPEX connector, both to connect the antenna. The antenna solder pin is flanked by two GND pins on either side.

Always operate this device with an antenna. If no designated antenna is at hand, use a plain 17.3cm wire. Operating this device without antenna can irreversibly damage the RF unit.


On the other end, five through-holes provide the connectivity. They are clearly marked on the back side:

Pin Tag Description
1 SET Input, internal 10K pull-up
2 TXD Output
3 RXD Input, internal 3.3K pull-up
4 GND negative voltage
5 VCC +3.2-5.5V

If the sender needs to transmit data for a lengthy time, and the power supply is >4.5V, then VCC should be reduced to no more than 4.5V, i.e. by connecting a 1N4007 diode in series to prevent over-heating.

Working Modes

The board supports the following transmission modes:

Mode Description Idle Current Serial Baud Air Baud Rate
FU1 Power Savings Mode 3.6mA 1200-115200 250kBps
FU2 Super Power Savings 80uA 1200-4800 250kBps
FU3 Normal 16mA 1200-115200 236kBps
FU4 Ultra Long Distance 16mA 1200 500bps

Transmission Speed

The serial baud rate controls the over the air baud rate.

Serial baud (bps) 1200-2400 4800-9600 19.2k-38.4k 57.6-115.2k
Wireless baud (Kbps) 5 15 58 236

Receiver Sensitivity

The faster the data transfer rate is, the lower is the receiver sensitivity:

Serial Baud (bps) 500 5k 15k 58k 236-250k
Receiver Sensitivity -124dBm -116dBm -111dBm -106dBm -100dBm

Communication distance reduces by half for every 6dBm decrese in receiver sensitivity.

Default Working Mode

By default, the module uses transmission mode FU3: the module works at full speed, and the over the air transmission rate is adjusted to the speed of the serial port baud rate.


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(content created Apr 01, 2024)