使用SAM E54的打印机示例在USB上写入USB

Question

我试图使用Microchip https://github.com/microchip-mplab-harmony/usb_apps_device/tree/master/master/master/printer_basic#config_9 。我想收到MCU的答案。我想设置一个USB_DEVICE_PRINTER_WRITE。

我决定在app.c中修改代码如下：

case APP_STATE_SCHEDULE_WRITE:

    /* Setup the write */
              
    appData.writeTransferHandle = USB_DEVICE_PRINTER_TRANSFER_HANDLE_INVALID;
    appData.state = APP_STATE_WAIT_FOR_WRITE_COMPLETE;
    /* Reset Switch Pressed status */
    appData.isSwitchPressed = false;
               
    printerResult = USB_DEVICE_PRINTER_Write(USB_DEVICE_PRINTER_INDEX_0,
        &appData.writeTransferHandle, (void*)&appData.prntrReadBuffer[0],
        APP_READ_BUFFER_SIZE,USB_DEVICE_PRINTER_TRANSFER_FLAGS_DATA_COMPLETE);
    
    if(printerResult== USB_DEVICE_PRINTER_RESULT_ERROR_INSTANCE_NOT_CONFIGURED)
    {
        LED_Toggle();
    }      
    break;

我总是将以下结果作为打印机：usb_device_printer_rinter_error_error_error_instance_not_configured，

是否缺少某些东西？

还有其他参考吗？