function sosibitsub(spo,bit,mode)

%    SOSI-M2 V1.0 MATLAB M-file
%
% Set channel mode to analog, digital input, or digital output
%
% Arguments: sosibit(spo,bit,mode)
%
% spo: serial port object
% bit: channel 0 - 6
% mode:  'ai'  analog input
%        'do' digital output
%        'di' digital input

delayt=0.1;

% set up channel number string
s1=sprintf('#sec%d',bit)

% Set up mode and I/O strings
if mode(1)=='a'
    s2='#a';           % analog
elseif mode(1)=='d'
    s2='#d';
    if mode(2)=='o'
        s3='#o';
    elseif mode(2)=='i'
        s3='#i';
    else
        disp('error: (mode) string');
        return;
    end
else
    disp('error: (mode) string');
    return;
end


cmd(spo,s1,delayt);                % Set channel number
cmd(spo,s2,delayt);                % Set channel type
if mode(1)=='d'
    cmd(spo,s3,delayt);            % Set I/O if digital
end

cmd(spo,'#e',0.5);              % exit, extra delay

% Set output channel state
% s3=sprintf('#o%dh',bit);        % output n high
% s4=sprintf('#o%dl',bit);        % output n low
% cmd(spo,s3,delayt);

return;