MATLAB Examples

Write and Read Fixed-Point Data from Binary Files in Simulink

The Binary File Writer and Binary File Reader blocks do not support writing and reading fixed-point data. As a workaround, you can write the stored integer portion of the fi data, read the data, and use this value to reconstruct the fi data.

Contents

Write the Fixed-Point Data

Create a fi object to represent 100 signed random numbers with a word length of 14 and a fraction length of 12.

data = randn(100,1);
fiDataWriter = fi(data,1,14,12);
storeIntData = storedInteger(fiDataWriter);

Write the stored integer portion of the fi object to the data file myFile.dat. The built-in data type is int16, which can be computed using class(storeIntData).

writeModel = fullfile(matlabroot,'examples','dsp','writeFixedData');
open_system(writeModel)
sim(writeModel)

Read the Fixed-Point Data

Specify the reader to read the stored integer data as int16 data with 100 samples per data frame.

readModel = fullfile(matlabroot,'examples','dsp','readFixedData');
open_system(readModel)
sim(readModel)

The real-world value of the fixed-point number can be represented using 2^[-fractionLength*storedInteger]. If you know the signedness, word length, and fraction length of the fixed-point data, you can reconstruct the fi data using fi(realValue,signedness,wordLength,fractionLength). In this example, the data is signed with a word length of 14 and a fraction length of 12.

fractionLength = 12;
wordLength = 14;
realValue = 2^(-fractionLength)*double(dataRead);
fiDataReader = fi(realValue,1,wordLength,fractionLength);

Verify that the writer data is same as the reader data.

isequal(fiDataWriter,fiDataReader)
ans =

  logical

   1