Hi,
nice projet. I am very interested in it.
But why you are using 5 V and not 3.3 V? The ATmea328 works with 3.3 V too and the NRF have to use 3.3 V.
The only restriction on 3.3 V is the clock limitation for the Atmega (8 MHz). But with no crystal it don't care.
For example you could use an HLK-PM03 instead of HLK-PM01 and remove the linear voltage regulator. So you get more space an everything have the same voltage level.
And another point is, it is recommended to use a capacitor (0.1 µF) to ground for each voltage pin (Vcc, Avcc, Aref).
@Sunseeker According to the Connecting the Radio page, D2 is the default pin for the CE signal for the NRF24. If you'd like to use this pin for I2C, you can free it up by assigning a different pin for the CE signal by adding this line to your sketch:
#define MY_RF24_CE_PIN pin
IIRC, all available pins should work for this purpose (D0, D3, D4). Just pick one and if it doesn't work, use one of the other pins. Please make sure to add that line before #include <MySensors.h>.
