The Crazyflie Packet eXchange protocol is used to send data to/from the GAP8 from/to other target systems, like the STM32, ESP32 or the host computer. For more information on the inner workings of CPX, have a look at the CPX documentation.
Using CPX
The CPX API available in the GAP8 can be viewed in the cpx.h header file. From here it’s possible to send/receive messages as well as print text to the Crazyflie client console. This API is for the original ESP32 firmware.
CPX in NanoCockpit
NanoCockpit has its own CPX implementation for the GAP8, in nanocockpit/lib/cpx, which works with the ESP32 firmware for NanoCockpit. It only supports communication between the GAP8 and the computer, through the ESP32: there is no route to the Crazyflie and no console in the Crazyflie client. The cpx component example shows how to use it.