Some files to batch convert snap-master generated SMA files, using a slightly customized version of EEGLAB's snapread() function.

batchConvertSMA.m

% batchConvertSMA() - Convert all SMA files in current directory and
%                     sub-directories to CSV files. Additionally extract the
%                     header and save as a txt file.

function [data,params,head,events] = batchConvertSMA() 

% Grab all SMA files in current directory and sub-directories
files = dir('**/*.SMA');

% count number of SMA files
numOfFiles = length(files);

% loop through each file
for i=1:numOfFiles
    % get current file
    currentFile = files(i);
    fprintf('\n Converting %s ...\n',currentFile.name);

    % generate paths to read/write to
    pathToRead = strcat(currentFile.folder,'/',currentFile.name);
    pathToWriteCSV = strcat(currentFile.folder,'/',strrep(currentFile.name,'SMA','csv'));
    pathToWriteTXT = strcat(currentFile.folder,'/',strrep(currentFile.name,'SMA','txt'));
    
    % use custom readsnap function
    [data,params,header] = readsnap(pathToRead);

    % write csv file
    dlmwrite(pathToWriteCSV,data, 'precision',30);

    % write header file
    dlmwrite(pathToWriteTXT,header,'delimiter','');
end

readsnap.m

% readsnap() - Read data in Snap-Master Standard Binary Data File Format
%              Reads Snap-Master header and data matrix (nchans,nframes).
%              Ref: Users Guide, Snap-Master for Windows (1997) p. 4-19
%              Note: This is an *altered* version of the original snapread
%              found in EEGLAB. 
% Usage:
%           >> data = readsnap(filename);  % read .SMA file data
%           >> [data,params,head,events] = readsnap(filename,seekframes); 
%                                          % save parameters, event list
% Inputs:
%        filename   = string containing whole filename of .SMA file to read
%        seekframes = skip this many initial time points {default 0}
% Output:
%        data   = data matrix, size(nchans,nframes)
%        params = [nchannels, nframes, srate]
%        head   = complete char file header 
%        events = vector of event frames (lo->hi transitions on event channel);
%                 See source to set EVENT_CHANNEL and EVENT_THRESH. 
%
% Note: This is based off the original snapread() found in EEGLAB. This version
% reverses the ordering of the output arguments, so that we can always return
% the params and header of file without having to split into events.
% 
% Author of Revision: Diego Mesa, La Jolla, October 20, 2016
% Original Authors: Scott Makeig & Tzyy-Ping Jung, SCCN/INC/UCSD, La Jolla,
% January 31, 2000
%
% Please see the original version for copyright information

function [data,params,head,events] = readsnap(file,seekframes) 

EVENT_CHANNEL = 1;   % This channel assumed to store event pulses only!
EVENT_THRESH  = 2.3; % Default event threshold (may need to adjust!!!!)

if nargin < 2
 seekframes = 0;
end 
data   = [];
events = [];
params = [];
head   = [];
%
%%%%%%%%%%%%%%%%%%%%%%%%%% Open file %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
fid = fopen(file,'r', 'ieee-le');
if fid<1
  fprintf('\nreadsnap(): Could not open file %s.\n\n',file)
  return
else
  fprintf('\n  Opened file %s for reading...\n',file);
end

%
%%%%%%%%%%%%%%%%%%%%%%%%%% Read header %%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Read header and extract info

numbegin=0;
head = [];
while ~numbegin,
  line =fgets(fid);
  head = [head line];
  if (length(line)>=8 & line(1:8)=='"NCHAN%"') 
      nchans=str2num(line(findstr(line,'=')+1:end-1));
  end
  if (length(line)>= 12 & line(1:12)=='"NUM.POINTS"') 
      nframes=str2num(line(findstr(line,'=')+1:end-1));
  end
  if (length(line)>= 10 & line(1:10)=='"ACT.FREQ"') 
      srate=str2num(line(findstr(line,'=')+1:end-1));
  end
  if (length(line)>= 4 & line(1:4)=='"TR"') 
     head = head(1:length(head)-length(line));
     line =fgets(fid); % get the time and date stamp line
     numbegin=1;
  end
end
params = [nchans, nframes, srate];
fprintf('  Number of channels:    %d\n',nchans);
fprintf('  Number of data points: %d\n',nframes);
fprintf('  Sampling rate:         %3.1f Hz\n',srate);

fseek(fid,1,0); % skip final hex-AA char

%
%%%%%%%%%%%%%%%%%%% Test for correct file length %%%%%%%%%%%%%%%%%%%%
%
datstart = ftell(fid); % save current position in file
fseek(fid,0,'eof');    % go to file end
datend = ftell(fid);   % report position
discrep = (datend-datstart) - nchans*nframes*4;
if discrep ~= 0
   fprintf(' ***> Note: File length does not match header information!\n')
   fprintf('            Difference: %g frames\n',discrep/(4*nchans));
end
fseek(fid,datstart,'bof'); % seek back to data start
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Read data %%%%%%%%%%%%%%%%%%%%%%%%%%
%

if seekframes > 0
  fprintf('  Omitting first %d frames of data.\n',seekframes)
  fprintf('moving %d bytes\n',seekframes*nchans*4);
  fsq = fseek(fid,seekframes*nchans*4,'cof')
  if fsq<0
    fsqerr = ferror(fid);
    fprintf('fseek() error: %s\n',fsqerr);
    return
  end
end

[data count] = fread(fid,[nchans,nframes],'float'); % read data frame
if count<nchans*(nframes-seekframes)
  fprintf('\nreadsnap(): Could not read %d data frames.\n             Only %g read.\n\n',...
       nframes,count/nchans);
  return
else
  fprintf('\n  Read %d frames, each one sync channel(%d) and %d data channels.\n',...
       nframes,EVENT_CHANNEL,nchans-1);
end

if nargout>3
  fprintf('  Finding event transitions (>%g) on channel %d ...\n',...
                             EVENT_THRESH,EVENT_CHANNEL);
  events = zeros(EVENT_CHANNEL,nframes);
  for n=2:nframes
     if abs(data(EVENT_CHANNEL,n-1)) < EVENT_THRESH ...
        & abs(data(EVENT_CHANNEL,n)) > EVENT_THRESH
             events(n) = 1;
     end
  end
  fprintf('  Total of %d events found.\n',sum(events));
  data = data(2:nchans,:);  % eliminate channel 1
  fprintf('  Event channel %d removed from output.\n',EVENT_CHANNEL);
  params(1) = nchans-1;
end
fprintf('\n');
fclose('all');

To have a version of batchConvertSMA() that saves mat files instead of csv, make the following changes:

%  pathToWriteCSV = strcat(currentFile.folder,'/',strrep(currentFile.name,'SMA','csv'));
    pathToWriteMAT = strcat(currentFile.folder,'/',strrep(currentFile.name,'SMA','mat'));   
...
% write MAT file
    save(pathToWriteMAT,'data')