update RAK811_LoRaNode firmware version to 2.x.3.3
Adjust duty cycle to improve the user experience.
update RAK811_LoRaNode firmware version to 2.x.3.2
1.Fix a debug about "The Hard Fault exception occurs,Reset!".
2.The end number in version indicate the version with DEBUG or RELEASE :odd:DEBUG ,even:RELEASE.
RAK811_LoRaNode firmware version 2.x.3.1
1.RAK811 is a LoRaNode module based on STM32L151 and SX1276. It has two kinds of boards : RAK811-HF board and RAK811-LF board.
2.This Firmware is based on LoRaWAN 1.0.2 protocol ,support Class A and Class C mode.User could switch the mode by such as 'at+set_config=class:2' command,0:class A,1:class B(unsupported),2:class C.
Tips:It supports almost all frequency bands:(HF)->EU868, US915, AU915, KR920, AS923，IN865.
(LF)->EU433，CN470.
3.The AT Command folder contains two firmware: "RAK811_HF.bin"and"RAK811_LF.bin".
"RAK811_HF.bin" surpport region:EU868, US915, AU915, KR920, AS923，IN865.
"RAK811_LF.bin" surpport region:EU433，CN470.
Tips： Region switch by such as"at+band=EU868"command，
details about AT command refer to RAK811 Lora AT Command V1.4.pdf.
4.Method of The Demo project generates different firmware refer to ReleaseNotes.txt.