USB Library
USBUSARTIsTxTrfReady Macro
Syntax
#define USBUSARTIsTxTrfReady (cdc_trf_state == CDC_TX_READY)
Description

This macro is used to check if the CDC class handler firmware is ready to send more data to the host over the CDC bulk IN endpoint. 

Typical Usage:

    if(USBUSARTIsTxTrfReady())
    {
        putrsUSBUSART("Hello World");
    }
Preconditions

The return value of this function is only valid if the device is in a configured state (i.e. - USBDeviceGetState() returns CONFIGURED_STATE)

Remarks

Make sure the application periodically calls the CDCTxService() handler, or pending USB IN transfers will not be able to advance and complete.

MLA - USB Library Help Version : 2.16
http://www.microchip.com/mla