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PDM clock frequency control

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This commit is contained in:
Quentin Smith
2022-08-21 02:16:26 -04:00
parent 029713eca0
commit ed97e61dbe
2 changed files with 18 additions and 8 deletions
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13
examples/nrf/src/bin/pdm_continuous.rs
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@ -5,8 +5,7 @@
use defmt::info;
use embassy_executor::Spawner;
use embassy_nrf::interrupt;
use embassy_nrf::pdm::{Config, Channels, Pdm, SamplerState};
use embassy_nrf::timer::Frequency;
use embassy_nrf::pdm::{Config, Channels, Pdm, SamplerState, Frequency, Ratio};
use fixed::types::I7F1;
use num_integer::Roots;
use {defmt_rtt as _, panic_probe as _};
@ -18,11 +17,13 @@ async fn main(_p: Spawner) {
let mut 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.channels = Channels::Mono;
config.gain_left = I7F1::from_bits(5); // 2.5 dB
let mut pdm = Pdm::new(p.PDM, interrupt::take!(PDM), &mut p.P0_00, &mut p.P0_01, config);
let mut bufs = [[0; 500]; 2];
let mut bufs = [[0; 1024]; 2];
pdm
.run_task_sampler(
@ -34,13 +35,15 @@ async fn main(_p: Spawner) {
// 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;
info!(
"{} samples, min {=i16}, max {=i16}, RMS {=i16}",
"{} samples, min {=i16}, max {=i16}, mean {=i16}, AC RMS {=i16}",
buf.len(),
buf.iter().min().unwrap(),
buf.iter().max().unwrap(),
mean,
(
buf.iter().map(|v| i32::from(*v).pow(2)).fold(0i32, |a,b| a.saturating_add(b))
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,
);
SamplerState::Sampled