otMacCounters::mTxErrCca field

The total number of CCA failures. The meaning of this counter can be different and it depends on the platform's radio driver capabilities. If OT_RADIO_CAPS_CSMA_BACKOFF is enabled, this counter represents the total number of full CSMA/CA failed attempts and it is incremented by one also for each retransmission (in case of a CSMA/CA fail). If OT_RADIO_CAPS_TRANSMIT_RETRIES is enabled, this counter represents the total number of full CSMA/CA failed attempts and it is incremented by one for each individual data frame request (regardless of the amount of retransmissions).