探索者下载测试程序时，串口有时显示：Device In suspend mode

Lxinyuan

在给stm32f407的板子下测试程序后，串口为什么有时显示：Device In suspend mode. 这段文字只有在这里的代码有 void HAL_PCD_SuspendCallback(PCD_HandleTypeDef *hpcd)
{
    g_device_state = 0;
    printf("Device In suspend mode.\r\n");
    USBD_LL_Suspend((USBD_HandleTypeDef*)hpcd->pData);
    __HAL_PCD_GATE_PHYCLOCK(hpcd);

    if (hpcd->Init.low_power_enable)
    {
        /* Set SLEEPDEEP bit and SleepOnExit of Cortex System Control Register. */
        SCB->SCR |= (uint32_t)((uint32_t)(SCB_SCR_SLEEPDEEP_Msk | SCB_SCR_SLEEPONEXIT_Msk));
    }
}