Let’s now connect the Q Brain to the flight controller. There are four connections from the Q Brain to the flight controller that allow the KK2.1 to control the four motors. To start the process, disconnect Q Brain’s wires from the connection hub we were using earlier and set the connection hub aside.
Like the connections for the radio receiver, each connection on the KK2.1 for the Q Brain has three pins: a ground pin, a power pin, and a signal pin. Also like the connections for the radio receiver, only one power and one ground connection is needed. That is why, if you examine the colored wires from the Q Brain, you will notice that, even though each is connected to a three-pin female connector, only one actually has three wires connected to it, because only one ground and one power connection is needed.
There are two problems however. First, the order of the motors around the quadcopter does not match the order expected by the KK2.1 flight control board. Fortunately, this is an easy problem to fix; we will just modify the order in which we plug the Q Brain signal wires into the flight controller. We’ll do that a bit later. The second problem is a bit trickier to solve. Although the fact that only one of the four plugs incorporates power and ground connections saves wire, the power and ground connections are attached to the wrong plug. The KK2.1 flight controller only takes power through the Output 1 connection, so we will need to make sure that the power and ground wires plug into the appropriate spots.
Let’s fix this second problem now. What we are going to do is detach the power and ground wires from the Motor 3 plug, and re-attach them to the Motor 4 plug because the Motor 4 plug will actually go into the Output 1 spot. More on that later, for now, just follow these instructions: