I've been working on this idea of building my own transmitter for my RC devices. One of the first things that I needed to do was build a nRF24 Multipro to talk with the RC devices. This will allow me to concentrate on the building the transmitter and not worry about building the RF code. With Multipro I can just send it a PPM signal and Multipro will do everything else to talk with the RC device (handle binding and device choice). I wanted to make sure that I understood how Multipro works so I implemented the simpliest solution possible. Having an Arduino talk with the Multipro via PPM.
The idea is simple. For the Multipro we need to connect a Arduino to the an nRF24 chip. No external chips are required other than the nRF24 since the Arduino supports 3.3V needed by the nRF24.
Here is the pin layout to connect the nRF24 to the Multipro:
GND - GND
VCC - 3.3V
CE - D5
CS - A1
SCK - D4
MOSI - D3
MISO - A0
IRQ - NC
After that we need a way to interface with the Multipro via a PPM signal. Another Arduino running custom code.
Just program an Arduino with the above code and connect it to the Multipro like so:
D13 (PPM) - D2 (PPM)
GND - GND
Turn on the quad and restart the Multipro. It should bind and stop flashing. After that you can open up a serial port to the Joystick_to_ppm Arduino and you can type 1, 2, ...., 9 for throttle and 0 to set it back to 0. You should get something like below: