This is an example of using modbus library which is a project customized for STMkit in STM32CUBEIDE
To configure UART settings use cube as shown below
To use modbus library, It is initialized with initModbus function like below
#include "modbus.h"
int main(void)
{
//some initialization here
.
.
.
/* USER CODE BEGIN 2 */
//initialize modbus
initModbus();
//start getting data from uart by DMA
HAL_UARTEx_ReceiveToIdle_DMA(&huart1, mbBuffer, ASCII_FRAME_SIZE);
//add your coustom code here
/* USER CODE END 2 */
while(1){
}
}after initialization Microcontroller tries to get data from master by using DMA and then after getting data it calls a callback function
void HAL_UARTEx_RxEventCallback(UART_HandleTypeDef *huart, uint16_t Size)
{
uint8_t responseLength;
//pass received buffer **mbBuffer** and Size of it to process function "execute_modbus_command" then it fills response buffer "sendBuffer" and returns its size
responseLength=execute_modbus_command(mbBuffer, Size);
//transmit response buffer "sendBuffer" to output port
if(responseLength>0)//check if size is bigger than 0
HAL_UART_Transmit_DMA(&huart1, sendBuffer, responseLength);
//initialize UART port again to receive request from master
HAL_UARTEx_ReceiveToIdle_DMA(&huart1, mbBuffer, ASCII_FRAME_SIZE);
}
//this callback reset DMA connection in case of any error with UART
void HAL_UART_ErrorCallback(UART_HandleTypeDef *huart){
HAL_UARTEx_ReceiveToIdle_DMA(&huart1, mbBuffer, ASCII_FRAME_SIZE);
}as you can see it calls function execute_modbus_command and passes buffer of data to it everything else is done by library