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parse_imu.m
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parse_imu.m
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%% parse_imu.m
%
% Usage
% imu = parse_imu(dat_or_file)
% imu = parse_imu(dat_or_file, parse_nuc_timestamps)
% imu = parse_imu(... , 'progress', uiprogressdlg)
%
% Inputs
% - dat_or_file
% This can be a filename, cell array of filenames, the output of MATLAB's
% "dir" command, or an array of binary data.
%
% Optional Arguments
% - parse_nuc_timestamps (logical)
% | Flag to parse Nuc timestamps inserted into the IMU_timestamped* files from
% | ROSE deployments.
%
% Name-value pair arguments
% - 'progress'
% Specify a UI progress dialog handle to update it with progress information while
% parsing data.
%
% Outputs
% - imu
% Data structure containing IMU fields. The field and subfield structure matches
% the fields described in the LORD IMU manuals.
%
% Author
% - Dylan Winters (dylan.winters@oregonstate.edu)
function imu = parse_imu(dat_or_file,varargin)
%% Parse optional inputs
p = inputParser;
addOptional(p,'parse_nuc_timestamps',false,@(x) islogical(x))
addParameter(p,'progress',struct(),@(x) isa(x,'matlab.ui.dialog.ProgressDialog'));
parse(p,varargin{:});
progress = p.Results.progress;
parse_nuc_timestamps = p.Results.parse_nuc_timestamps;
%% Main parsing routine
% 1) Load binary data
if iscell(dat_or_file)
% Cell array of filenames
dat = load_data(dat_or_file);
elseif isstruct(dat_or_file)
% File info struct from dir()
dat = load_data(fullfile({dat_or_file.folder},{dat_or_file.name}));
elseif isstr(dat_or_file)
% Single filename
dat = load_data({dat_or_file});
else
% Treat input as raw data
dat = dat_or_file;
end
% 2) Locate & validate data packets
header = find_headers(dat,progress);
% 3) Convert binary data to struct
progress.Message = 'IMU: Processing data';
progress.Indeterminate = 'on';
imu = parse_data(header, dat);
progress.Indeterminate = 'off';
%%% Sub-functions
%----------------------------------------------------------
% Locate headers in the 3DM-GX5-25 binary output
%----------------------------------------------------------
function header = find_headers(dat,progress)
% Find sequences of SYNC1 and SYNC2 bytes (0x75,0x65).
% These are the first two bytes of all headers.
h = find(dat(1:end-1) == hex2dec('75') & ...
dat(2:end) == hex2dec('65'));
% Throw out trailing headers with no payload
h = h(length(dat) - h > 2);
% Look for timestamps inserted by ROSE computer
if parse_nuc_timestamps
% Discard first header if preceeding timestamp is incomplete
if ~isempty(h)
if h(1) < 8
h = h(2:end);
end
ts = double(dat(h - [7:-1:1]));
ts(:,1) = ts(:,1) + 2000; % add century
ts(:,6) = ts(:,6) + ts(:,7)/100; % add ms to s
ts = datenum(ts(:,1:6));
else
ts = [];
end
end
% The third byte is the 'descriptor set', which signifies the payload type.
d = double(dat(h + 2));
% The fourth byte is the payload length.
l = double(dat(h + 3));
% Verify checksums of each packet payload
kp = true(size(h));
progress.Message = 'IMU: Validating checksums...';
for n = 1:length(h);
% Stop if we reach EoF before packet end
if h(n) + l(n)-1 + 6 <= length(dat)
% Extract packet payload
pp = dat(h(n) + [0:l(n)+3]);
% Extract packet checksum
chk1 = double(dat((h(n) + l(n)+3) + [1:2]));
chk1 = bitshift(chk1(1),8) + chk1(2);
% Compute packet checksum (16-bit Fletcher checksum)
sum1 = 0;
sum2 = 0;
for i = 1:length(pp)
sum1 = mod(sum1 + double(pp(i)),2^8);
sum2 = mod(sum2 + sum1,2^8);
end
chk2 = bitshift(sum1,8) + sum2;
% Discard packet if checksums don't match
if chk2 ~= chk1
kp(n) = false;
end
else % EoF reached before packet end; discard
kp(n) = false;
end
if mod(n,500) == 1;
progress.Value = n/length(h);
end
end
progress.Value = 1;
progress.Message = 'IMU: Validating checksums... Done!';
% Eliminate headers with invalid checksums
header.index = h(kp);
header.descriptor = d(kp);
header.length = l(kp);
if parse_nuc_timestamps
header.ts = ts(kp);
end
end
%----------------------------------------------------------
% Read and concatenate data in the given list of files
%----------------------------------------------------------
function dat = load_data(files,progress)
dat = [];
for i = 1:length(files)
if ~exist(files{i},'file')
error('File not found: %s',files{i})
end
[~,fname,fext] = fileparts(files{i});
progress.Message = sprintf('IMU: Opening %s%s [%d of %d]',fname,fext,i,length(files));
progress.Value = i/length(files);
fd = fopen(files{i},'r','ieee-le');
dat = cat(1,dat,uint8(fread(fd,inf,'uint8')));
fclose(fd);
end
end
%----------------------------------------------------------
% Convert raw binary data to a MATLAB struct
%----------------------------------------------------------
function output = parse_data(header, dat)
if length(header) == 0
output = [];
return
end
output = struct(); % initialize output structure
output.units = struct(); % initialize units structure
[d, f, id] = unique(header.descriptor);
len = header.length(f);
dat_preproc = cell(length(d),1);
for i = 1:length(d)
dat_preproc{i} = dat(header.index(id==i)+2 + [0:len(i)+1]);
end
for i = 1:length(d) % for each type of payload encountered while finding headers...
nb_proc = 2;
while nb_proc < size(dat_preproc{i},2) % extract fields 1-by-1
flen = unique(dat_preproc{i}(:,nb_proc+1)); % get field length
fdesc = unique(dat_preproc{i}(:,nb_proc+2)); % and descriptor
[dname fname subfields] = imu_field_defs(d(i),fdesc); % get subfield info
% initialize output fields/subfields
if ~isfield(output,dname)
output.(dname) = struct();
% store ROSE timestamps
if parse_nuc_timestamps
output.(dname).nuc_time = header.ts(id==i);
end
end
if ~isfield(output.(dname),fname)
output.(dname).(fname) = struct();
end
for sf = 1:length(subfields)
% store unit information
output.units.(dname).(fname).(subfields(sf).name) = subfields(sf).units;
% compute subfield length
if sf==length(subfields)
sf_len = flen-2 - subfields(end).offset;
else
sf_len = subfields(sf+1).offset - subfields(sf).offset;
end
% compute subfield index in pre-processed data
sf_idx = nb_proc + 3 + subfields(sf).offset + [0:sf_len-1];
% convert 8-bit integers to final datatype with MATLAB's typecast function
% this requires some reshaping, etc. to be fast
output.(dname).(fname).(subfields(sf).name) = ...
double(typecast(reshape(fliplr(dat_preproc{i}(:,sf_idx))',1,[]),subfields(sf).type));
end
nb_proc = nb_proc + double(flen);
end
end
end % of parse_data()
%----------------------------------------------------------
% Define subfield names, byte offsets, subfield lengths, and
% datatypes based on the payload descriptor.
%----------------------------------------------------------
function [dname fname subfields] = imu_field_defs(descriptor,fdesc)
dname = '';
fname = '';
subfields = struct();
switch dec2hex(descriptor,2) % Descriptor set byte
case '80' % IMU Data
dname = 'IMU';
switch dec2hex(fdesc,2)
case '04'
fname = 'scaled_accelerometer_vector';
subfields = struct(...
'name', {'x_accel','y_accel','z_accel'},...
'offset', {0,4,8},...
'type', {'single','single','single'},...
'units', {'g','g','g'});
case '05'
fname = 'scaled_gyro_vector';
subfields = struct(...
'name', {'x_gyro','y_gyro','z_gyro'},...
'offset', {0,4,8},...
'type',{'single','single','single'},...
'units',{'rad/s','rad/s','rad/s'});
case '06'
fname = 'scaled_magnetometer_vector';
subfields = struct(...
'name', {'x_mag','y_mag','z_mag'},...
'offset', {0,4,8},...
'type',{'single', 'single', 'single'},...
'units', {'gauss','gauss','gauss'});
case '17'
fname = 'scaled_ambient_pressure';
case '07'
fname = 'delta_theta_vector';
case '08'
fname = 'delta_velocity_vector';
case '09'
fname = 'cf_orientation_matrix';
case '0A'
fname = 'cf_quaternion';
case '0C'
fname = 'cf_euler_angles';
subfields = struct(...
'name', {'roll','pitch','yaw'},...
'offset', {0,4,8},...
'type', {'single','single','single'},...
'units', {'radians','radians','radians'});
case '10'
fname = 'cf_stabilized_north_vector';
case '11'
fname = 'cf_stabilized_up_vector';
case '12'
fname = 'gps_correlation_timestamp';
subfields = struct(...
'name', {'gps_time_of_week','gps_week_number','timestamp_flags'},...
'offset', {0,8,10},...
'type', {'double','uint16','uint16'},...
'units', {'seconds','n/a','see manual'});
end
case '81' % GNSS Data
dname = 'GNSS';
switch dec2hex(fdesc,2)
case '03'
fname = 'llh_position';
subfields = struct(...
'name', {'latitude' ,...
'longitude',...
'height_above_ellipsoid',...
'height_above_msl',...
'horizontal_accuracy',...
'vertical_accuracy',...
'valid_flags'} ,...
'offset',{0,8,16,24,32,36,40},...
'type', {'double',...
'double',...
'double',...
'double',...
'single',...
'single',...
'uint16'},...
'units', {'decimal degrees',...
'decimal degrees',...
'meters',...
'meters',...
'meters',...
'meters',...
'see manual'});
case '04'
fname = 'position_eath_centered_earth_fixed_frame';
subfields = struct(...
'name', {'x_pos','y_pos','z_pos','pos_accuracy','valid_flags'},...
'offset', {0,8,16,24,28},...
'type', {'double','double','double','single','uint16'},...
'units',{'meters','meters','meters','meters','see manual'});
case '05'
fname = 'velocity_north_east_down_frame';
subfields = struct(...
'name', {'north',...
'east',...
'down',...
'speed',...
'ground_speed',...
'heading',...
'speed_accuracy',...
'heading_accuracy',...
'valid_flags'},...
'offset', {0,4,8,12,16,20,24,28,32},...
'type', {'single',...
'single',...
'single',...
'single',...
'single',...
'single',...
'single',...
'single',...
'uint16'},...
'units', {'m/sec',...
'm/sec',...
'm/sec',...
'm/sec',...
'm/sec',...
'decimal degrees',...
'm/sec',...
'decimal degrees',...
'see manual'});
case '06'
fname = 'velocity_eath_centered_earth_fixed_frame';
subfields = struct(...
'name', {'x_vel','y_vel','z_vel','vel_accuracy','valid_flags'},...
'offset', {0,4,8,12,16},...
'type', {'single','single','single','single','uint16'},...
'units',{'m/sec','m/sec','m/sec','m/sec','see manual'});
case '07'
fname = 'DOP_data';
case '08'
fname = 'UTC_time';
subfields = struct(...
'name',{'year','month','day','hour','minute','second',...
'millisecond','valid_flags'},...
'offset',{0,2,3,4,5,6,7,11},...
'type',{'uint16','uint8','uint8','uint8','uint8',...
'uint8','uint32','uint16'},...
'units',{'years','months','days','hours','minutes',...
'seconds','milliseconds','see manual'});
case '09'
fname = 'GPS_time';
subfields = struct(...
'name',{'time_of_week','week_number','valid_flags'},...
'offset',{0,8,10},...
'type',{'double','uint16','uint16'},...
'units',{'seconds','n/a','see manual'});
case '0A'
fname = 'clock_information';
case '0B'
fname = 'gnss_fix_information';
case '0C'
fname = 'space_vehicle_information';
case '0D'
fname = 'hardware_status';
case '0E'
fname = 'dgnss_information';
case '0F'
fname = 'dgnss_channel_status';
end
case '82' % Estimation Filter (Attitude) Data
dname = 'attitude';
switch dec2hex(fdesc,2)
case '10'
fname = 'filter_status';
case '11'
fname = 'gps_timestamp';
subfields = struct(...
'name', {'time_of_week' ,...
'week_number' ,...
'valid'} ,...
'offset',{0,8,10} ,...
'type', {'double' ,...
'uint16' ,...
'uint16'} ,...
'units', {'seconds' ,...
'n/a' ,...
'1=valid, 0=invalid'});
case '03'
fname = 'orientation_quaternion';
case '12'
fname = 'attitude_uncertainty_quaternion_elements';
case '05'
fname = 'orientation_euler_angles';
subfields = struct(...
'name', {'roll' ,...
'pitch' ,...
'yaw' ,...
'valid'} ,...
'offset',{0,4,8,12} ,...
'type', {'single' ,...
'single' ,...
'single' ,...
'uint16'} ,...
'units', {'radians' ,...
'radians' ,...
'radians' ,...
'1=valid, 0=invalid'});
case '0A'
fname = 'attitude_uncertainty_euler_angles';
case '04'
fname = 'orientation_matrix';
case '0E'
fname = 'compensated_angular_rate';
subfields = struct(...
'name', {'X' ,...
'Y' ,...
'Z' ,...
'valid'} ,...
'offset',{0,4,8,12} ,...
'type', {'single' ,...
'single' ,...
'single' ,...
'uint16'} ,...
'units', {'rads/sec' ,...
'rads/sec' ,...
'rads/sec' ,...
'1=valid, 0=invalid'});
case '06'
fname = 'gyro_bias';
case '0B'
fname = 'gyro_bias_uncertainty';
case '1C'
fname = 'compensated_acceleration';
case '0D'
fname = 'linear_acceleration';
subfields = struct(...
'name', {'X' ,...
'Y' ,...
'Z' ,...
'valid'} ,...
'offset',{0,4,8,12} ,...
'type', {'single' ,...
'single' ,...
'single' ,...
'uint16'} ,...
'units', {'m/sec^2' ,...
'm/sec^2' ,...
'm/sec^2' ,...
'1=valid, 0=invalid'});
case '21'
fname = 'pressure_altitude';
case '13'
fname = 'gravity_vector';
case '0F'
fname = 'wgs84_local_gravity_magnitude';
case '14'
fname = 'heading_update_source_state';
subfields = struct(...
'name', {'heading' ,...
'heading_1_sigma_uncertainty' ,...
'source' ,...
'valid'} ,...
'offset',{0,4,8,10} ,...
'type', {'single' ,...
'single' ,...
'uint16' ,...
'uint16'} ,...
'units', {'radians' ,...
'radians' ,...
'0=no source, 1=Magnetometer, 4=External',...
'1=valid, 0=invalid'});
case '15'
fname = 'magnetic_model_solution';
case '25'
fname = 'mag_auto_hard_iron_offset';
case '28'
fname = 'mag_auto_hard_iron_offset_uncertainty';
case '26'
fname = 'mag_auto_soft_iron_matrix';
case '29'
fname = 'mag_auto_soft_iron_matrix_uncertainty';
end
end
end % of imu_field_defs
end % of parse_imu()