kopia lustrzana https://github.com/proto17/dji_droneid
Converted the create_burst script to a function
David Protzman
rodzic
40a604dd23
commit
60ea2b16bc
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@ -1,185 +1,160 @@
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sample_rate = 15.36e6;
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show_debug_plots = 0;
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%% Build payload
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% Example:
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% create_frame_bytes('SequenceNumber', uint16(1234), ...
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% 'SerialNumber', '!this is a test!');
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frame_bytes = create_frame_bytes('SerialNumber', '!this is a test!');
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%% Turbo encoding and rate matching
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% Get the location of this script
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if (is_octave)
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this_script_path = fileparts(mfilename('fullpath'));
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else
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this_script_path = fileparts(matlab.desktop.editor.getActiveFilename);
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end
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% Make sure that the `add_turbo` binary exists. If it doesn't then you need to make sure you have compiled the
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% dji_droneid/cpp folder
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add_turbo_path = fullfile(this_script_path, '..', '..', '..', 'cpp', 'add_turbo');
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if (~ isfile(add_turbo_path))
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error("Could not find Turbo encoder application at '%s'. Check that the program has been compiled",...
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add_turbo_path);
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end
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% Where to store the files used to talk to the add_turbo binary
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frame_bin_file = '/tmp/frame.bin'; % Will write payload bytes here
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turbo_encoded_file = '/tmp/frame.bin.encoded'; % The add_turbo binary will create this
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% Write out the payload to Turbo encode and rate match
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file_handle = fopen(frame_bin_file, "w");
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fwrite(file_handle, frame_bytes, 'uint8');
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fclose(file_handle);
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% Call the Turbo encoder
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[retcode, out] = system(sprintf("%s '%s' '%s'", add_turbo_path, frame_bin_file, turbo_encoded_file));
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if (retcode ~= 0)
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warning("Failed to run the Turbo encoder. Details: %s", out);
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end
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% Verify that it created the expected output file
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if (~ isfile(turbo_encoded_file))
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error("Turbo encoder did not produce an output file");
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end
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% Read in all bytes from the encoded output file
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file_handle = fopen(turbo_encoded_file, "r");
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encoded_bits = uint8(fread(file_handle, inf, 'uint8'));
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fclose(file_handle);
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% Make sure that there are exactly the right number of bytes in the file created by the Turbo encoder
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required_bytes = 7200;
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if (length(encoded_bits) ~= required_bytes)
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error("Expected %d bytes, but got %d", required_bytes, length(encoded_bits))
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end
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%% Scrambler Application
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% Convert to a matrix of 8 rows so that each symbol has it's own row
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encoded_bits = reshape(encoded_bits, [], 6).';
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% Initial value for the second LFSR in the scrambler
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scrambler_x2_init = fliplr([0 0 1, 0 0 1 0, 0 0 1 1, 0 1 0 0, 0 1 0 1, 0 1 1 0, 0 1 1 1, 1 0 0 0]);
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% Create scrambler for all data bits and reshape so that each OFDM symbol has a row
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scrambler = uint8(reshape(generate_scrambler_seq(7200, scrambler_x2_init), [], 6).');
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encoded_bits = [scrambler(1,:); encoded_bits];
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% Apply the scrambler to each OFDM symbol's data bits
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for idx=1:6
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encoded_bits(idx+1,:) = bitxor(encoded_bits(idx+1,:), scrambler(idx,:));
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end
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%% OFDM Symbol Creation Setup
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% There are two variants I know of right now. One that uses 9 OFDM symbols (my DJI Mini 2) and others that use 8
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% symbols. To keep life simple, I am using the 8 symbol version as it doesn't require modulating an OFDM symbol that
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% doesn't get used anyway.
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% TODO(23April2022): Come back to this and support 9 symbols
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assert(use_9_symbols == 0, "Currently only support creation of 8 symbols")
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% Get some required params
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fft_size = get_fft_size(sample_rate);
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[long_cp_len, short_cp_len] = get_cyclic_prefix_lengths(sample_rate);
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% Define the size of each symbols cyclic prefix
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cyclic_prefix_schedule = [
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long_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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long_cp_len ...
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];
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% Number of data carriers per OFDM symbol
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data_carrier_count = 600;
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%% Bits to Symbol Mapping
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% Create the QPSK samples for each OFDM symbol
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symbol_data = zeros(9, data_carrier_count);
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encoded_bits_ptr = 1;
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for symbol_idx=1:9
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% There's no work to be done for symbols 4 and 6 as they are ZC sequences
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if (symbol_idx == 4)
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elseif (symbol_idx == 6)
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else
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% Convert from bits to QPSK constellation
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symbol_data(symbol_idx,:) = to_qpsk(encoded_bits(encoded_bits_ptr,:));
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encoded_bits_ptr = encoded_bits_ptr + 1;
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end
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if (show_debug_plots)
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figure(1);
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subplot(3, 3, symbol_idx);
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plot(symbol_data(symbol_idx,:), 'o');
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end
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end
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%% Frequency Domain Symbol Creation
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% Create the frequency domain representation of each OFDM symbol
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freq_domain_symbols = zeros(9, fft_size);
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% Get the carriers that will contain the QPSK samples
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data_carrier_indices = get_data_carrier_indices(sample_rate);
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for symbol_idx=1:9
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% Copy the freq domain samples to the buffer
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freq_domain_symbols(symbol_idx,data_carrier_indices) = symbol_data(symbol_idx,:);
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if (show_debug_plots)
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figure(2);
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subplot(3, 3, symbol_idx);
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plot(abs(freq_domain_symbols(symbol_idx,:)).^2);
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function [samples] = create_burst(sample_rate, frame_configuration, add_turbo_path, show_debug_plots)
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frame_bytes = create_frame_bytes(frame_configuration{:});
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figure(3);
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subplot(3, 3, symbol_idx);
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plot(freq_domain_symbols(symbol_idx,:), 'o');
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%% Turbo encoding and rate matching
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if (~ isfile(add_turbo_path))
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error("Could not find Turbo encoder application at '%s'. Check that the program has been compiled",...
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add_turbo_path);
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end
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% Where to store the files used to talk to the add_turbo binary
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frame_bin_file = '/tmp/frame.bin'; % Will write payload bytes here
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turbo_encoded_file = '/tmp/frame.bin.encoded'; % The add_turbo binary will create this
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% Write out the payload to Turbo encode and rate match
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file_handle = fopen(frame_bin_file, "w");
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fwrite(file_handle, frame_bytes, 'uint8');
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fclose(file_handle);
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% Call the Turbo encoder
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[retcode, out] = system(sprintf("%s '%s' '%s'", add_turbo_path, frame_bin_file, turbo_encoded_file));
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if (retcode ~= 0)
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warning("Failed to run the Turbo encoder. Details: %s", out);
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end
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% Verify that it created the expected output file
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if (~ isfile(turbo_encoded_file))
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error("Turbo encoder did not produce an output file");
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end
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% Read in all bytes from the encoded output file
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file_handle = fopen(turbo_encoded_file, "r");
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encoded_bits = uint8(fread(file_handle, inf, 'uint8'));
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fclose(file_handle);
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% Make sure that there are exactly the right number of bytes in the file created by the Turbo encoder
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required_bytes = 7200;
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if (length(encoded_bits) ~= required_bytes)
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error("Expected %d bytes, but got %d", required_bytes, length(encoded_bits))
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end
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%% Scrambler Application
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% Convert to a matrix of 8 rows so that each symbol has it's own row
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encoded_bits = reshape(encoded_bits, [], 6).';
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% Initial value for the second LFSR in the scrambler
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scrambler_x2_init = fliplr([0 0 1, 0 0 1 0, 0 0 1 1, 0 1 0 0, 0 1 0 1, 0 1 1 0, 0 1 1 1, 1 0 0 0]);
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% Create scrambler for all data bits and reshape so that each OFDM symbol has a row
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scrambler = uint8(reshape(generate_scrambler_seq(7200, scrambler_x2_init), [], 6).');
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encoded_bits = [scrambler(1,:); encoded_bits];
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% Apply the scrambler to each OFDM symbol's data bits
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for idx=1:6
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encoded_bits(idx+1,:) = bitxor(encoded_bits(idx+1,:), scrambler(idx,:));
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end
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%% OFDM Symbol Creation Setup
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% Get some required params
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fft_size = get_fft_size(sample_rate);
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[long_cp_len, short_cp_len] = get_cyclic_prefix_lengths(sample_rate);
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% Define the size of each symbols cyclic prefix
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cyclic_prefix_schedule = [
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long_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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short_cp_len, ...
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long_cp_len ...
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];
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% Number of data carriers per OFDM symbol
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data_carrier_count = 600;
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%% Bits to Symbol Mapping
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% Create the QPSK samples for each OFDM symbol
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symbol_data = zeros(9, data_carrier_count);
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encoded_bits_ptr = 1;
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for symbol_idx=1:9
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% There's no work to be done for symbols 4 and 6 as they are ZC sequences
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if (symbol_idx == 4)
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elseif (symbol_idx == 6)
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else
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% Convert from bits to QPSK constellation
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symbol_data(symbol_idx,:) = to_qpsk(encoded_bits(encoded_bits_ptr,:));
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encoded_bits_ptr = encoded_bits_ptr + 1;
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end
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if (show_debug_plots)
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figure(1);
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subplot(3, 3, symbol_idx);
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plot(symbol_data(symbol_idx,:), 'o');
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end
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end
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%% Frequency Domain Symbol Creation
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% Create the frequency domain representation of each OFDM symbol
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freq_domain_symbols = zeros(9, fft_size);
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% Get the carriers that will contain the QPSK samples
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data_carrier_indices = get_data_carrier_indices(sample_rate);
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for symbol_idx=1:9
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% Copy the freq domain samples to the buffer
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freq_domain_symbols(symbol_idx,data_carrier_indices) = symbol_data(symbol_idx,:);
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if (show_debug_plots)
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figure(2);
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subplot(3, 3, symbol_idx);
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plot(abs(freq_domain_symbols(symbol_idx,:)).^2);
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figure(3);
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subplot(3, 3, symbol_idx);
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plot(freq_domain_symbols(symbol_idx,:), 'o');
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end
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end
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%% Time Domain Symbol Creation
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% Create the time domain representation of each OFDM symbol (no cyclic prefix at this point)
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time_domain_symbols = zeros(9, fft_size);
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for symbol_idx=1:9
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time_domain_symbols(symbol_idx,:) = ifft(fftshift(freq_domain_symbols(symbol_idx,:)));
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if (show_debug_plots)
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figure(4);
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subplot(3, 3, symbol_idx);
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plot(10 * log10(abs(time_domain_symbols(symbol_idx,:)).^2))
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end
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end
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time_domain_symbols(4,:) = create_zc(fft_size, 4);
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time_domain_symbols(6,:) = create_zc(fft_size, 6);
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samples = [];
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for symbol_idx=1:9
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cp_len = cyclic_prefix_schedule(symbol_idx);
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symbol = time_domain_symbols(symbol_idx,:);
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cp = symbol(end-cp_len+1:end);
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samples = [samples, cp, symbol];
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end
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end
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%% Time Domain Symbol Creation
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% Create the time domain representation of each OFDM symbol (no cyclic prefix at this point)
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time_domain_symbols = zeros(9, fft_size);
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for symbol_idx=1:9
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time_domain_symbols(symbol_idx,:) = ifft(fftshift(freq_domain_symbols(symbol_idx,:)));
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if (show_debug_plots)
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figure(4);
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subplot(3, 3, symbol_idx);
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plot(10 * log10(abs(time_domain_symbols(symbol_idx,:)).^2))
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figure(7);
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plot(10 * log10(abs(time_domain).^2));
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filter_out = filter(conj(create_zc(fft_size, 4)), 1, samples);
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figure(8);
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plot(abs(filter_out).^2);
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end
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end
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time_domain_symbols(4,:) = create_zc(fft_size, 4);
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time_domain_symbols(6,:) = create_zc(fft_size, 6);
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time_domain = [];
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for symbol_idx=1:9
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cp_len = cyclic_prefix_schedule(symbol_idx);
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symbol = time_domain_symbols(symbol_idx,:);
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cp = symbol(end-cp_len+1:end);
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time_domain = [time_domain, cp, symbol];
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end
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time_domain = awgn([zeros(1, 10000), time_domain, zeros(1, 10000)], 60);
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write_complex_floats('/tmp/burst.fc32', time_domain);
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if (show_debug_plots)
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figure(7);
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plot(10 * log10(abs(time_domain).^2));
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filter_out = filter(conj(create_zc(fft_size, 4)), 1, time_domain);
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figure(8);
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plot(abs(filter_out).^2);
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end
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