root/branches/workshop/Accelerator/GetAccelerator.m @ 34

function [acc_vector] = GetAccelerator(f_sensorport)

%% Build hex command and send it with NXT_LSWrite
    %-----------------------------LSWRITE----------------------------------

    % create this I2C command. basically all we want to do is request 1
    % byte, the current sensor reading!
    
    RequestLen = 6;
    I2Cdata = hex2dec(['02'; '42']); % Read Measurement Byte 0 (see LEGO Mindstorms NXT 
                                     % Ultrasonic Sensor - I2C Communication Protocol)
    
        NXT_LSWrite(f_sensorport, RequestLen, I2Cdata, 'dontreply')
    
    %----------------------------------------------------------------------
    
    
%% Get current processing status of digital sensor    
    %---------------------------LSGETSTATUS--------------------------------;
    
    % we keep on asking the NXT when the ultrasonic sensor is ready...
    % note the dangerous potential of an infinite loop in case the sensor
    % should never get ready...
    
    BytesReady = 0;
    while (BytesReady == 0)
        %TODO some sort of timeout in here in case we never get an answer?
        [BytesReady status] = NXT_LSGetStatus(f_sensorport);
    end%if
    
    acc_vector = -1;

%% If ready get object distance (ultrasonic sensor value)    
    if ( status == 0 ) && ( BytesReady > 0 ) 
        
        %-------------------------LSREAD-----------------------------------
        
        [data BytesRead] = NXT_LSRead(f_sensorport);
        
        if BytesRead > 5
            if (data(1) > 127) data(1) = data(1) - 256; end
            if (data(2) > 127) data(2) = data(2) - 256; end
            if (data(3) > 127) data(3) = data(3) - 256; end
            acc_vector(1) = data(1) * 4 + data(4);
            acc_vector(2) = data(2) * 4 + data(5);
            acc_vector(3) = data(3) * 4 + data(6);
        end%if
        
        %------------------------------------------------------------------
    end%if
    
end%function