Can you tell me how to set up serial port in keil?

Keil is an IDE, it does not really matter. It is like any other project. I recommend using STM32CubeMX tool which you can download for free.

https://www.st.com/en/development-tools/stm32cubemx.html

With it comes several examples and the tool can create a basic project for you.

I have Cubemx. Can you tell me how to specify serial port with Cubemx?

Just play with the Cube, you will see. It is not hard.

Which serial port on what pins?

You might be better looking at the existing vcom.c code, or the USART/UART examples under the HAL trees for the NUCLEO board.

In the example of p-nucleo-lrwan1 pingpong, I want to add code and set it to UART4 rx, tx . Please help me.

I want to set USART4 on pc10, pc11.

void USART4_Init(void)
{
 static UART_HandleTypeDef UartHandle;
 GPIO_InitTypeDef GPIO_InitStruct;
 
 __USART4_CLK_ENABLE();
 __GPIOC_CLK_ENABLE()
 
 /* UART TX/RX GPIO pin configuration */
 GPIO_InitStruct.Pin = GPIO_PIN_10 | GPIO_PIN_11;
 GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
 GPIO_InitStruct.Pull = GPIO_PULLUP;
 GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
 GPIO_InitStruct.Alternate = GPIO_AF6_USART4;
 
 HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
 
 /*## Configure the UART peripheral ######################################*/
 /* Put the USART peripheral in the Asynchronous mode (UART Mode) */
 /* USART4 configured as follow:
 - Word Length = 8 Bits
 - Stop Bit = One Stop bit
 - Parity = No parity
 - BaudRate = 9600 baud
 - Hardware flow control disabled (RTS and CTS signals) */
 
 UartHandle.Instance = USART4;
 
 UartHandle.Init.BaudRate = 9600;
 UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
 UartHandle.Init.StopBits = UART_STOPBITS_1;
 UartHandle.Init.Parity = UART_PARITY_NONE;
 UartHandle.Init.HwFlowCtl = UART_HWCONTROL_NONE;
 UartHandle.Init.Mode = UART_MODE_TX_RX;
 
 if (HAL_UART_Init(&UartHandle) != HAL_OK)
 {
 /* Initialization Error */
 Error_Handler();
 }
 
// If you use interrupts
// HAL_NVIC_SetPriority(USART4_IRQn, 0x1, 0);
// HAL_NVIC_EnableIRQ(USART4_IRQn);
}

Thank you, but I'd like to use Interrupt but it says 'USART4_IRQn' is not defined. you help me?

L073RZ shares USART4 and 5 interrupts

HAL_NVIC_SetPriority(USART4_5_IRQn, 0x1, 0);

HAL_NVIC_EnableIRQ(USART4_5_IRQn);

..

void USART4_5_IRQHandler(void)

{

..

}

'.\sx1272mb2das\NUCLEO_CUBE_LORA.axf: Error: L6218E: Undefined symbol __HAL_RCC_UART4_CLK_ENABLE '

I didn't define 'HAL_RCC_UART4_CLK_ENABLE' but the same error appears above.What's the problem?