UM1545 datasheet(35/64 Pages) STMICROELECTRONICS

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UM1545

APW walkthrough

Doc ID 023225 Rev 1

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response. If this goal cannot be achieved, the import option will apply the best gains to

minimize the gain mismatch between the desired overall frequency response and the

actual response.

●

Enable auto-scaler (manual gain adjustment): the user is given the choice of the

attenuation to apply. The resulting global frequency response envelope will be

preserved, although attenuated by the selected gain. Under these circumstances the

attenuation might be compensated using the volume controls.

●

Disable auto-scaler (skip invalid filters, if any): the scaling procedure is disabled and the

filters that cannot be applied are skipped. The overall frequency response will differ

from the desired response.

Figure 35.

Filter import options

Once the scaling options are set, the filters are imported by pressing the Import filter button.

Before downloading any information into the device, the APW also performs a stability check

to prevent the user from applying unstable filters, thus causing dangerous and unpredictable

behaviors. At the end of the procedure a message will give the user the number of applied

coefficients. Invalid filter (whether instable or out of range) coefficients are skipped, each

time this happens a warning message appears. For further information about the import

process please refer to Appendix D: Filter import wizard.

2.9

Exporting filter coefficients

Filter coefficients can be imported but they can also be exported. The APW offers two export

formats:

●

C/C++ arrays format (.c file)

●

Matlab® arrays format (.m file)

The first format is very useful for MCU programming, while the second one might be used

for in-depth filter analysis. Left click on the File menu to enable these features (Figure 36).

Figure 36.

Exporting coefficients

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