sx1276 데이터 시트를 보다보니 CR(Coding Rate)라는게 있어서 먼지 감이 안와서(메뉴얼 상에서는) 찾아보니
FEC를 위한 추가 비트를 이야기 하고, 순수데이터/패리티포함데이터 길이로 보면 된다고 한다.
4/5는 4bit data + 1bit parity
4/6은 4bit data +2bit parity
4/7은 4bit data +3bit parity
4/8은 4bit data +4bit parity 식인셈
4.1.1.3. Coding Rate To further improve the robustness of the link the LoRa® modem employs cyclic error coding to perform forward error detection and correction. Such error coding incurs a transmission overhead - the resultant additional data overhead per transmission is shown in the table below.
Forward error correction is particularly efficient in improving the reliability of the link in the presence of interference. So that the coding rate (and so robustness to interference) can be changed in response to channel conditions - the coding rate can optionally be included in the packet header for use by the receiver. Please consult Section 4.1.1.6 for more information on the LoRa® packet and header.
