4 IN 1 RF module integrates four RF chips( CC2500， NRF24L01， A7105， CYRF6936 ) in one single PCB board.
It supports more than 10 different protocols while working with MCU board， such as Frsky， Flysky， Hisky， Devo， DSM2， V2x2 and so on.
You can use arduino nano to DIY your own MCU board， it also can be used with walkera devo transmitter.

Description:

1. Arduino promini 5V/16Mhz(Protocols are using as witness the existing on board LED on B5 pin). It can be used also any setup with Atmega328P/16Mhz.
2. A7105 module(X7105-D03 PA/LNA module， V911，V939 harvested TX modules)
3. CC2500 PA/LNA module
4. Nrf24L01 PA/LNA module
5. Devo module(based on CYRF6936)
6. AMS1117 -5V and AMS1117-3.3V， LDO voltage regulator or any other regulators over 800mA.
7. Resistor 20K(between NRF_CE pin to Vcc)
8. Caps 22-47uF(3 pcs on ldo's)
9. Rotary dip switch 16 positions or DIP switch 4 positions this is required only in PPM mode.
Now in the serial mode with er9x/ersky9x/opentx there is no need to use dial switch anymore.

Pin function:

Number	Name	Property	Description
1	VCC	Power	3.3V Power supply
2	GND	Power	ground
3	PE1	input	Switch for RF chips， See the truth table
4	PE2	input	Switch for RF chips， See the truth table
5	CSN1	input	A7105 chip select
6	CSN2	input	CC2500 chip select
7	CSN3	input	NRF24L01 chip select
8	CSN4	input	CYRF6936 chip select
9	SCK	input	SPI clock signal
10	MOSI	input	SPI input for slave device
11	MISO	output	SPI output for slave device
12	CYRF_RST	input	CYRF6936 Reset
16	RFO	in/out	RF signal， connect to antenna
others	GND	Power	ground

 
Truth table:

status	PE1	PE2
A7105 RF signal to antenna	Low level	Low level
CC2500 RF signal to antenna	Low level	high level
NRF24L01 RF signal to antenna	high level	Low level
CYRF6936 RF signal to antenna	high level	high level

For more information， please visit the RCG forum:
http://www.rcgroups.com/forums/showthread.php?t=2165676

Example for MCU Board:

Package included:

1 x DIY 2.4G CC2500 NRF24L01 A7105 CYRF6936 Multi RF 4 IN 1 Wireless Module