Re: [Discuss-gnuradio] Ettus N210 GMSK 9600

[Andy Walls]

Hi Tom,

The corr_est block needs to match against the NRZI encoded symbols, so yes I 
used 7 ones for the hdlc flag.

The HDLC flag has two possible NRZI encodings depending on the initial state:

  01111110   - HDLC flag byte
1 00000001  - NRZI encoded HDLC flag byte, initial state 1

  01111110  - HDLC flag byte
0 11111110  - NRZI encoded HDLC flag byte, initial state 0


So encoding your two byte sequence:

  01111110 00100001
1 00000001 01101011
or
0 11111110 10010100

You should build your corr_est preamble samples based on one of these.

Regards,
Andy