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8.9.2 FIR filter design software
The filter coefficients must be created with the aid of filter design software. miniDSP does not provide any such
software, instead referring you to the many software packages available for this purpose, both freeware and
commercial. See page 36 for an example using
rephase and the FIR filter tools page on our website for other
tools.
8.9.3 Loading filter coefficients in File Mode
This is the most likely usage method. Use your FIR filter design tool to generate the impulse response (filter
coefficients) for each FIR block. The file must use
IEEE 754 single-precision binary floating-point format . The
number of entries in the file must not exceed the allocated number of taps for the block.
1. Click Browse , navigate to the file containing the filter coefficients, and open it. A dialog will appear
confirming the number of coefficients loaded.
2. Confirm that the response curve is as you expect.
3. Press Send to DSP . This will write the coefficients into the DSP's memory.
4. To clear the filter coefficients, click Unload FIR and then Send to DSP .
8.9.4 Loading filter coefficients in Manual Mode
Filter coefficients can also be pasted in directly as text format, if the block is set to Manual Mode. In this mode,
the coefficients must be plain text in this format:
b0 = 1,
b1 = -1,
b2 = 0.5,
b3 = -0.5,
b4 = 0.2,
b5 = 1,
To load in Manual Mode:
1.
Cut and paste the coefficients from the text output of the design program.
2. Press the Process button.
3. Confirm that the frequency response graph is as you expect.
4. Press Send to DSP . This will write the coefficients into the DSP's memory.
5. To clear the filter coefficients, click Clear Taps and then Send to DSP .
If, after selecting a filter file or setting coefficients, the frequency response graph does not change as
expected, make sure that the Bypass button is turned off.
If you clear the filter taps, make sure that you also bypass the filter, otherwise there will be no audio
through that channel.