Lowpass Filter
The LowpassFilter class provides an implementation of a digial lowpass infinite impulse response (IIR) filter, which leverages the hardware acceleration provided by esp-dsp and which leverages the vector instructions on the espressif processors.
API Reference
Header File
Classes
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class LowpassFilter
Lowpass infinite impulse response (IIR) filter.
Public Functions
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LowpassFilter() = default
Default constructor.
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explicit LowpassFilter(const Config &config)
Initialize the lowpass filter coefficients based on the config.
- Parameters:
config – Configuration struct.
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void configure(const Config &config)
Set the filter coefficients based on the config.
- Parameters:
config – Configuration struct.
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void update(const float *input, float *output, size_t length)
Filter the input samples, updating internal state, and writing the filtered values to the data pointed to by output.
Note
On ESP32, the input and output arrays must have attribute((aligned(16))) to ensure proper alignment for the ESP32 DSP functions.
- Parameters:
input – Pointer to (floating point) array of new samples of the input data
output – Pointer to (floating point) array which will be filled with the filtered input.
length – Number of samples, should be >= length of input & output memory.
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float update(const float input)
Filter the signal sampled by input, updating internal state, and returning the filtered output.
- Parameters:
input – New sample of the input data.
- Returns:
Filtered output based on input and history.
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float operator()(float input)
Filter the signal sampled by input, updating internal state, and returning the filtered output.
- Parameters:
input – New sample of the input data.
- Returns:
Filtered output based on input and history.
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void reset()
Reset the filter state to zero.
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struct Config
Configuration for the lowpass filter.
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LowpassFilter() = default