instructions (if supported by the core) coupled
together with other optimisations allow
engineers to produce highly optimised signal
processing applications for Cortex-M based
micro-controllers quickly and simply.
ASN Filter Designer fully supports the CMSIS
DSP software framework, by automatically
producing optimised C code based on the
framework’s DSP functions via its code
generation engine. ASN Filter Designer
provides engineers with an easy to use, intuitive
graphical design development platform for both
IIR and FIR digital filter design. The tool’s realtime
design paradigm makes use of graphical
design markers, allowing designers to simply
draw and modify their magnitude frequency
response requirements in real-time while
allowing the tool automatically fill in the exact
specifications for them.
Consider the design of the following technical
Passband frequency: 0-40Hz
Stopband attenuation @ 125Hz: ≥ 80 dB
Passband ripple: < 0.1dB
Order: Small as possible
Figure 3. ASN filter designer: filter summary.
Graphically entering the specifications into the
ASN Filter Designer, and fine tuning the design
marker positions, the tool automatically designs
the filter as a Biquad cascade (see note below),
automatically choosing the required filter order,
and in essence - automatically producing the
filter’s exact technical specification.
The frequency response of a 5th order
IIR Elliptic Lowpass filter meeting the
specifications is shown in Figure 1. This 5th
order Lowpass filter will form the basis of the
discussion presented in the full version of this
article (see link).
18 DesignNews NOVEMBER 2017 www.eedesignnewseurope.com