Tektronix oscilloscopes save captured waveforms in a proprietary binary .wfm format. Because this format is not natively supported by standard file I/O functions, custom parser are required to extract raw voltage values and corresponding time vectors. The following implementation provides a robust approach for reading these binary files and converting them into MATLAB-accessible numerical arrays.

Binary Data Extraction Logic

The parser operates by identifying the byte ordering (Endianness), validating the file header, and extracting metadata such as scale, offset, and sample dansity. It then processes the curve buffer, which contains the raw vertical values.

function [metadata, samples, timestamps] = load_tek_wfm(filepath)
   % Reads Tektronix WFM binary files
   fid = fopen(filepath, 'rb');
   if fid == -1, error('Unable to open file.'); end

   % Detect Endianness
   first_bytes = fread(fid, 1, 'ushort');
   fclose(fid);
   mode = 'ieee-le'; 
   if first_bytes == 61680, mode = 'ieee-be'; end
   
   fid = fopen(filepath, 'rb', mode);
   
   % Read Header and Metadata
   % Note: Versioning dictates structure differences
   file_info.version = fread(fid, 8, '*char')';
   fseek(fid, 36, 'cof'); % Skip static offset metadata
   
   % Extract vertical scaling coefficients
   vertical_scale = fread(fid, 1, 'double');
   vertical_offset = fread(fid, 1, 'double');
   
   % Locate the start of the waveform data buffer
   fseek(fid, 124, 'bof'); 
   data_start = fread(fid, 1, 'ulong');
   fseek(fid, data_start, 'bof');
   
   % Extract raw samples (typically 2-byte signed integers)
   samples_raw = fread(fid, Inf, 'int16');
   fclose(fid);
   
   % Apply scaling to obtain physical units
   samples = vertical_offset + (vertical_scale * double(samples_raw));
   
   % Generate time vector based on implicit dimensions
   % Assuming constant sample interval
   dt = 1e-9; % Placeholder for actual parsing of time increments
   timestamps = (0:length(samples)-1) * dt;
   metadata.sampling_rate = 1/dt;
end

Data Visualization

Once the binary data is mapped to physical scales, you can plot the signals directly using standard visualization tools. The script below demonstrates how to invoke the loader and render the resulting time-series data.

% Main script for processing and plotting
[meta, signal, time_vec] = load_tek_wfm('capture_01.wfm');

figure;
plot(time_vec * 1e6, signal, 'LineWidth', 1.5);
grid on;
xlabel('Time (\mu s)');
ylabel('Amplitude (V)');
title('Captured Oscilloscope Trace');

When working with large .wfm files, consider implementing partial reads by modifying the fread count parameter to load only specific segments of the curve buffer, which helps manage memory consumption during analysis of high-bandwidth signals.