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#![no_std]
#![no_main]
use core::cmp::Ordering;
use defmt::info;
use embassy_executor::Spawner;
use embassy_nrf::pdm::{self, Config, Frequency, OperationMode, Pdm, Ratio, SamplerState};
use embassy_nrf::{bind_interrupts, peripherals};
use fixed::types::I7F1;
use microfft::real::rfft_1024;
use num_integer::Roots;
use {defmt_rtt as _, panic_probe as _};
// Demonstrates both continuous sampling and scanning multiple channels driven by a PPI linked timer
bind_interrupts!(struct Irqs {
PDM => pdm::InterruptHandler<peripherals::PDM>;
});
#[embassy_executor::main]
async fn main(_p: Spawner) {
let p = embassy_nrf::init(Default::default());
let mut config = Config::default();
// Pins are correct for the onboard microphone on the Feather nRF52840 Sense.
config.frequency = Frequency::_1280K; // 16 kHz sample rate
config.ratio = Ratio::RATIO80;
config.operation_mode = OperationMode::Mono;
config.gain_left = I7F1::from_bits(5); // 2.5 dB
let mut pdm = Pdm::new(p.PDM, Irqs, p.P0_00, p.P0_01, config);
let mut bufs = [[0; 1024]; 2];
pdm.run_task_sampler(&mut bufs, move |buf| {
// NOTE: It is important that the time spent within this callback
// does not exceed the time taken to acquire the 1500 samples we
// have in this example, which would be 10us + 2us per
// sample * 1500 = 18ms. You need to measure the time taken here
// and set the sample buffer size accordingly. Exceeding this
// time can lead to the peripheral re-writing the other buffer.
let mean = (buf.iter().map(|v| i32::from(*v)).sum::<i32>() / buf.len() as i32) as i16;
let (peak_freq_index, peak_mag) = fft_peak_freq(&buf);
let peak_freq = peak_freq_index * 16000 / buf.len();
info!(
"{} samples, min {=i16}, max {=i16}, mean {=i16}, AC RMS {=i16}, peak {} @ {} Hz",
buf.len(),
buf.iter().min().unwrap(),
buf.iter().max().unwrap(),
mean,
(buf.iter()
.map(|v| i32::from(*v - mean).pow(2))
.fold(0i32, |a, b| a.saturating_add(b))
/ buf.len() as i32)
.sqrt() as i16,
peak_mag,
peak_freq,
);
SamplerState::Sampled
})
.await
.unwrap();
}
fn fft_peak_freq(input: &[i16; 1024]) -> (usize, u32) {
let mut f = [0f32; 1024];
for i in 0..input.len() {
f[i] = (input[i] as f32) / 32768.0;
}
// N.B. rfft_1024 does the FFT in-place so result is actually also a reference to f.
let result = rfft_1024(&mut f);
result[0].im = 0.0;
result
.iter()
.map(|c| c.norm_sqr())
.enumerate()
.max_by(|(_, a), (_, b)| a.partial_cmp(b).unwrap_or(Ordering::Equal))
.map(|(i, v)| (i, ((v * 32768.0) as u32).sqrt()))
.unwrap()
}
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