问题 ： 使用printf串口1没有任何输出

已经在RTE_device.h中启用USART功能
已经添加Compiler(I/O:STDOUT)
已经调用stdout_init初始化

附代码
串口初始化代码：
[mw_shl_code=c,true]
#include "Driver_USART.h"
#include "stdout_usart.h"
#include "stdio.h"

//-------- <<< Use Configuration Wizard in Context Menu >>> --------------------

// <h>STDOUT USART Interface

//   <o>Connect to hardware via Driver_USART# <0-255>
//   <i>Select driver control block for USART interface
#define USART_DRV_NUM           1

//   <o>Baudrate
#define USART_BAUDRATE          115200

// </h>


#define _USART_Driver_(n)  Driver_USART##n
#define  USART_Driver_(n) _USART_Driver_(n)

extern ARM_DRIVER_USART  USART_Driver_(USART_DRV_NUM);
#define ptrUSART       (&USART_Driver_(USART_DRV_NUM))


/**
  Initialize stdout

   eturn          0 on success, or -1 on error.
*/
int stdout_init (void) {
  int32_t status;

  status = ptrUSART->Initialize(NULL);
  if (status != ARM_DRIVER_OK) return (-1);

  status = ptrUSART->PowerControl(ARM_POWER_FULL);
  if (status != ARM_DRIVER_OK) return (-1);

  status = ptrUSART->Control(ARM_USART_MODE_ASYNCHRONOUS |
                             ARM_USART_DATA_BITS_8       |
                             ARM_USART_PARITY_NONE       |
                             ARM_USART_STOP_BITS_1       |
                             ARM_USART_FLOW_CONTROL_NONE,
                             USART_BAUDRATE);
  if (status != ARM_DRIVER_OK) return (-1);

  status = ptrUSART->Control(ARM_USART_CONTROL_TX, 1);
  if (status != ARM_DRIVER_OK) return (-1);

  return (0);
}


/**
  Put a character to the stdout

  param[in]   ch  Character to output
   eturn          The character written, or -1 on write error.
*/
int stdout_putchar (int ch) {
  uint8_t buf[1];

  buf[0] = ch;
  if (ptrUSART->Send(buf, 1) != ARM_DRIVER_OK) {
    return (-1);
  }
  while (ptrUSART->GetTxCount() != 1);
  return (ch);
}
[/mw_shl_code]