Editing Default Header Format Obj.

[[Category:Block Docs]]
Default header formatter for PDU formatting. Used to handle the default packet header.

See the parent class header_format_base for details of how these classes operate.

The default header created in this base class consists of an access code and the packet length. The length is encoded as a 16-bit value repeated twice:

  | access code | hdr | payload |

Where the access code is <= 64 bits and hdr is:

  |  0 -- 15 | 16 -- 31 |
  | pkt len  | pkt len  |

The access code and header are formatted for network byte order.

This header generator does not calculate or append a CRC to the packet. Use the CRC32 Async block for that before adding the header. The header's length will then measure the payload plus the CRC length (4 bytes for a CRC32).

The default header parser produces a PMT dictionary that contains the following keys. All formatter blocks MUST produce these two values in any dictionary.

See [https://www.gnuradio.org/doc/doxygen/classgr_1_1digital_1_1header__format__default.html] for more info.

== Parameters ==
; Access Code
: An access code that is used to find and synchronize the start of a packet. Used in the parser and in other blocks like a corr_est block that helps trigger the receiver. Can be up to 64-bits long. 

; Threshold
: How many bits can be wrong in the access code and still count as correct. 

; Payload Bits per Symbol
: The number of bits/second used in the payload's modulator. 

== Example Flowgraph ==

Insert description of flowgraph here, then show a screenshot of the flowgraph and the output if there is an interesting GUI.  Currently we have no standard method of uploading the actual flowgraph to the wiki or git repo, unfortunately.  The plan is to have an example flowgraph showing how the block might be used, for every block, and the flowgraphs will live in the git repo.

== Source Files ==

; C++ files
: [https://github.com/gnuradio/gnuradio TODO]

; Header files
: [https://github.com/gnuradio/gnuradio TODO]

; Public header files
: [https://github.com/gnuradio/gnuradio TODO]

; Block definition
: [https://github.com/gnuradio/gnuradio TODO]