char str[1024] = { 0 };
int main(void) {
   MX_USART1_UART_Init();
   MX_USART2_UART_Init();
   HAL_UARTEx_ReceiveToIdle_IT(&huart1, str, 1024);
   while (1) {
   }
}
static void MX_USART1_UART_Init(void) {

   /* USER CODE BEGIN USART1_Init 0 */

   /* USER CODE END USART1_Init 0 */

   /* USER CODE BEGIN USART1_Init 1 */

   /* USER CODE END USART1_Init 1 */
   huart1.Instance = USART1;
   huart1.Init.BaudRate = 9600;
   huart1.Init.WordLength = UART_WORDLENGTH_8B;
   huart1.Init.StopBits = UART_STOPBITS_1;
   huart1.Init.Parity = UART_PARITY_NONE;
   huart1.Init.Mode = UART_MODE_TX_RX;
   huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
   huart1.Init.OverSampling = UART_OVERSAMPLING_16;
   if (HAL_UART_Init(&huart1) != HAL_OK) {
      Error_Handler();
   }
   /* USER CODE BEGIN USART1_Init 2 */

   /* USER CODE END USART1_Init 2 */

}

/**
 * @brief USART2 Initialization Function
 * @param None
 * @retval None
 */
static void MX_USART2_UART_Init(void) {

   /* USER CODE BEGIN USART2_Init 0 */

   /* USER CODE END USART2_Init 0 */

   /* USER CODE BEGIN USART2_Init 1 */

   /* USER CODE END USART2_Init 1 */
   huart2.Instance = USART2;
   huart2.Init.BaudRate = 115200;
   huart2.Init.WordLength = UART_WORDLENGTH_8B;
   huart2.Init.StopBits = UART_STOPBITS_1;
   huart2.Init.Parity = UART_PARITY_NONE;
   huart2.Init.Mode = UART_MODE_TX_RX;
   huart2.Init.HwFlowCtl = UART_HWCONTROL_NONE;
   huart2.Init.OverSampling = UART_OVERSAMPLING_16;
   if (HAL_UART_Init(&huart2) != HAL_OK) {
      Error_Handler();
   }
   /* USER CODE BEGIN USART2_Init 2 */

   /* USER CODE END USART2_Init 2 */

}

void HAL_UARTEx_RxEventCallback(UART_HandleTypeDef *huart, uint16_t Size) {
   if (huart->Instance == USART1) {
      HAL_UART_Transmit_IT(&huart2, str, Size);
      HAL_UARTEx_ReceiveToIdle_IT(&huart1, str, 1024);
   }
}

Name : str
   Details:"b", '\0' <repeats 1022 times>

    GPIO_InitStruct.Pin = GPIO_PIN_7;
    GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);