How to communicate between HC-12 using STM32

HC-12 wireless serial port communication module is a new-generation multichannel embedded wireless data transmission module. Its wireless working frequency band is 433.4-473.0MHz, multiple channels can be set, with the stepping of 400 KHz, and there are totally 100 channels. The maximum transmitting power of module is 100mW (20dBm), the receiving sensitivity is -117dBm at baud rate of 5,000bps in the air, and the communication distance is 1,000m in open space.

I will be using the modules in the default setup. The parameters are as shown below

• Here Baud Rate is 9600
• Channel selected is1
• Transmitting Power is 20dBm
• and mode selected is FU3

you can see the datasheet for more information on how to change these parameters. But i think the default setup is pretty good and it gives you a fairly good communication range also.

CubeMX Setup

I am going to use the Uart Ring Buffer to communicate between the two HC-12 modules. These modules will be connected to the 2 different microcontrollers, and both of them will be using the same code. And that’s why I will just show the CubeMX setup for only one of them

Above is the Setup for the UART1, where the HC-12 will be connected. I have selected the baud rate of 9600 as HC-12 is working at same Baud Rate. Also make sure that you turn on the interrupt. The connection between HC-12 and Microcontroller will be shown below in the connection section

Above is the setup for UART2, which is connected to the computer

The exact same setup is needed for the second microcontroller too. For more information, check the video at the end of this post.

Connection

• Vcc is connected to 5V
• Gnd to Gnd
• Tx from the HC-12 is connected to the Rx from the MCU
• and Rx from HC-12 to Tx from the MCU
• SET pin must be left as it is for communication, and while using AT commands, we must Ground it

Those, who have errors in the Uart_isr function, like DR or SR registers are not present, or L4 series and G series MCUs have some issues with UART_ISR_TXE. To resolve them, visit https://controllerstech.com/managing-multiple-uarts-in-stm32/
and do what the UPDATE section have mentioned

Some Insight into the code

After generating the project, you have to include the library files into the project. Basically UartRingbuffer_multi.c file will go in the src folder and UartRingbuffer_multi.h file will go in the inc folder.

First of all I have defined the new names to the UART handlers as shown below

#define device_uart &huart1
#define pc_uart &huart2

Next we need to initialize the ring buffer in the main function

Ringbuf_init();

In the while loop, if the controller receives the data from device, it will send it to the PC. And if it receives the data from the PC, it will send it to the device. This way it will act as a mediator in between device and computer.

 while (1)
  {
    if (IsDataAvailable(pc_uart))
    {
     int data = Uart_read(pc_uart);
     Uart_write(data, device_uart);
    }

    if (IsDataAvailable(device_uart))
    {
     int data = Uart_read(device_uart);
     Uart_write(data, pc_uart);
    }
  }

Result

• In the above picture, both the MCUs are using different com ports.
• The Pink color is the one you send, and the black color is the one receive.
• As you can see, the data sent from the first MCU is being received by the second, and vice versa