The Crazyradio dongle is based on a Nordic semiconductor nRF24LU1 chip. The radio communication is done using the Nordic “Enhanced ShockBurst™” packet protocol with acknoledge. Variable size packet, from 1 to 32 bytes, can be send and acknoledged by the copter. The acknoledgement packet can contains a payload from 0 to 32Bytes.

This page document the protocol used in the version 0.33 of the Crazyradio dongle. Future version (up to 1.0) will be kept compatible.

The USB devices have the VID/PID couple 0x1915/0x7777. Two bulk endpoint are configured:

The radio dongle is configured in PTX mode (in the Nordic terminology) which means that it sends packet to the copter and waits for the acknowledge. The acknowledge can contains a Payload which is the mean to get data from the copter.

The packet is to send is sent to the EP1 and the ack status is then received from the EP1. There are no buffering in the radio dongle, the ACK must be received by the PC before the next packet can be sent.