add example flowgraph for modulating sync word

examples/modulate_sync_word.grc

+options:
+  parameters:
+    author: ''
+    catch_exceptions: 'True'
+    category: '[GRC Hier Blocks]'
+    cmake_opt: ''
+    comment: ''
+    copyright: University of Melbourne
+    description: ''
+    gen_cmake: 'On'
+    gen_linking: dynamic
+    generate_options: qt_gui
+    hier_block_src_path: '.:'
+    id: modulate_sync_word
+    max_nouts: '0'
+    output_language: python
+    placement: (0,0)
+    qt_qss_theme: ''
+    realtime_scheduling: ''
+    run: 'True'
+    run_command: '{python} -u {filename}'
+    run_options: prompt
+    sizing_mode: fixed
+    thread_safe_setters: ''
+    title: Modulate Sync Word
+    window_size: (1000,1000)
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [8, 8]
+    rotation: 0
+    state: enabled
+
+blocks:
+- name: constel
+  id: variable_constellation
+  parameters:
+    comment: ''
+    const_points: '[-1-1j, -1+1j, 1+1j, 1-1j]'
+    dims: '1'
+    normalization: digital.constellation.AMPLITUDE_NORMALIZATION
+    precision: '8'
+    rot_sym: '4'
+    soft_dec_lut: None
+    sym_map: '[0, 1, 3, 2]'
+    type: bpsk
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [184, 12.0]
+    rotation: 0
+    state: true
+- name: excess_bw
+  id: variable
+  parameters:
+    comment: ''
+    value: '0.35'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [728, 12.0]
+    rotation: 0
+    state: true
+- name: nsamps
+  id: variable
+  parameters:
+    comment: ''
+    value: sps*nsymbs
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [824, 12.0]
+    rotation: 0
+    state: true
+- name: nsymbs
+  id: variable
+  parameters:
+    comment: ''
+    value: 8*len(preamble)//constel.bits_per_symbol()
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [504, 12.0]
+    rotation: 0
+    state: true
+- name: ntaps
+  id: variable
+  parameters:
+    comment: ''
+    value: 11*sps
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [656, 12.0]
+    rotation: 0
+    state: true
+- name: preamble
+  id: variable
+  parameters:
+    comment: ''
+    value: digital.packet_utils.default_access_code_binary
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [344, 12.0]
+    rotation: 0
+    state: true
+- name: sps
+  id: variable
+  parameters:
+    comment: ''
+    value: '2'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [584, 12.0]
+    rotation: 0
+    state: true
+- name: analog_const_source_x_0
+  id: analog_const_source_x
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    const: '0'
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    type: complex
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [520, 180.0]
+    rotation: 0
+    state: true
+- name: blocks_file_sink_0
+  id: blocks_file_sink
+  parameters:
+    affinity: ''
+    alias: ''
+    append: 'False'
+    comment: "Saves modulate sync word samples to \nbinary file. You can load in Python\
+      \ using \nnumpy:\n\nnumpy.fromfile(<filename>, dtype=np.complex64)"
+    file: modulated_sync_word.bin
+    type: complex
+    unbuffered: 'False'
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [528, 260.0]
+    rotation: 180
+    state: true
+- name: blocks_head_0
+  id: blocks_head
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    num_items: nsamps
+    type: complex
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [760, 276.0]
+    rotation: 180
+    state: true
+- name: blocks_packed_to_unpacked_xx_0
+  id: blocks_packed_to_unpacked_xx
+  parameters:
+    affinity: ''
+    alias: ''
+    bits_per_chunk: constel.bits_per_symbol()
+    comment: ''
+    endianness: gr.GR_MSB_FIRST
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    num_ports: '1'
+    type: byte
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [216, 116.0]
+    rotation: 0
+    state: true
+- name: blocks_skiphead_0
+  id: blocks_skiphead
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: 'Skip ramp up samples of RRC
+
+      transmit pulse-shaping filter'
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    num_items: ntaps//2
+    type: complex
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [920, 276.0]
+    rotation: 180
+    state: true
+- name: blocks_stream_mux_0
+  id: blocks_stream_mux
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    lengths: (nsymbs, ntaps//2)
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    num_inputs: '2'
+    type: complex
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [696, 128.0]
+    rotation: 0
+    state: true
+- name: blocks_vector_source_x_0
+  id: blocks_vector_source_x
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    repeat: 'True'
+    tags: '[]'
+    type: byte
+    vector: '[int(x) for x in preamble]'
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [8, 108.0]
+    rotation: 0
+    state: true
+- name: digital_chunks_to_symbols_xx_0
+  id: digital_chunks_to_symbols_xx
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    dimension: '1'
+    in_type: byte
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    num_ports: '1'
+    out_type: complex
+    symbol_table: constel.points()
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [504, 112.0]
+    rotation: 0
+    state: true
+- name: root_raised_cosine_filter_0
+  id: root_raised_cosine_filter
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha: excess_bw
+    comment: ''
+    decim: '1'
+    gain: '1.0'
+    interp: sps
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    ntaps: ntaps
+    samp_rate: sps
+    sym_rate: '1.0'
+    type: interp_fir_filter_ccf
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [848, 100.0]
+    rotation: 0
+    state: true
+
+connections:
+- [analog_const_source_x_0, '0', blocks_stream_mux_0, '1']
+- [blocks_head_0, '0', blocks_file_sink_0, '0']
+- [blocks_packed_to_unpacked_xx_0, '0', digital_chunks_to_symbols_xx_0, '0']
+- [blocks_skiphead_0, '0', blocks_head_0, '0']
+- [blocks_stream_mux_0, '0', root_raised_cosine_filter_0, '0']
+- [blocks_vector_source_x_0, '0', blocks_packed_to_unpacked_xx_0, '0']
+- [digital_chunks_to_symbols_xx_0, '0', blocks_stream_mux_0, '0']
+- [root_raised_cosine_filter_0, '0', blocks_skiphead_0, '0']
+
+metadata:
+  file_format: 1