hdlc 프로토콜 - bit stuffing, endian?

아.. 이런 변수가 하나 더 있었던 건가..

111111 가 전송되려면 1111101 이런식으로 전송되어야 한다.

(그런데.. 진짜 데이터가 111110 이면 어떡해야 하지? 어짜피 5개가 되었으니 1111100이 되는건가?)

Because a flag sequence consists of six consecutive 1-bits, other data is coded to ensure that it never contains more than five 1-bits in a row. This is done by bit stuffing: any time that five consecutive 1-bits appear in the transmitted data, the data is paused and a 0-bit is transmitted. HDLC transmits bytes of data with the least significant bit first (not to be confused with little-endian order, which refers to byte ordering within a multi-byte field).

[링크 : https://en.wikipedia.org/wiki/High-Level_Data_Link_Control]

 

The NRZI coding scheme transmits a 0 bit as a signal transition, and a 1 bit as no change. In this case, bit stuffing is most easily described as the insertion of a 0 bit after a long run of 1 bits.

[링크 : https://en.wikipedia.org/wiki/Bit_stuffing]

 

[링크 : https://copycode.tistory.com/79]

[링크 : https://itwiki.kr/w/HDLC]

[링크 : https://goodgid.github.io/What-is-HDLC/]

 

+

 

 

0,1 눈대중으로 변환해서 연속된 0이나 1에 대한 오류가 존재하지만

전반적으로 비트가 뒤집힌 형태로 전송됨을 확인함. (바이트 내에서 LSB가 MSB에 존재함)

7E 11 22 33 1E 0A 7F 01111110 00010001 00100010 00110011 00011110 00001010 01111111 (raw) 01111110 10110100 10010110 10001000 10111110 10100110 01111111 (nrzi) 11111110 01011010 11010010 00100010 11111010 11001010 11111110 (수신데이터) 01111111 01011010 01001011 01000100 01011111 01010011 01111111 (수신데이터 바이트 단위 순서 변경)