Here is the schematic of BeWi based on Atmega168 and NRF24l01+:

1. Atmega168 read sensor data
   
2. Atmega168 use SPI to talk to NRF24l01+ and send 2.4G BLE beacon packets
3. Atmega168 control AO6604 to enable/disable battery charging.
4. Atmega168 read battery voltage and decide when to charge, keep battery voltage low can greatly extend battery life
5. HT7333 provide power to Atmega168 and NRF24l01+
6. C2 is 0.22F super capacitor, depends on the setup, it can power BeWi alone with small solar module