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# 2.5.3.2 USB_DEVICE_CDC_QUEUE_DEPTH_COMBINED Macro

## C

    #define USB_DEVICE_CDC_QUEUE_DEPTH_COMBINED

## Summary

USB device CDC Combined Queue Size

This macro defines the number of entries in all queues in all instances of the CDC function driver. This value can be obtained by adding up the read and write queue sizes of each CDC Function driver instance. In a simple single instance USB CDC device application, that does not require buffer queuing and serial state notification, the USB_DEVICE_CDC_QUEUE_DEPTH_COMBINED macro can be set to 2. Consider a case with two CDC function driver instances, CDC 1 has a read queue size of 2 and write queue size of 3, CDC 2 has a read queue size of 4 and write queue size of 1, this macro should be set to 10 (2 +3 + 4 + 1).