median-filter the samples before sending them over itm
we're limited by the itm busrate. but we can at least get a cleaner signal by sampling at a higher rate and then downsampling before sending to the PC.
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parent
0695b22d4f
commit
749ffc0411
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@ -8,6 +8,7 @@ version = "0.1.0"
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cortex-m = "0.5.6"
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cortex-m-rt = "0.6.3"
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panic-itm = "0.4.0"
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pdqsort = "1.0"
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[dependencies.f3]
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features = ["rt"]
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@ -8,6 +8,7 @@ itm-to-pcm.py dump.txt dump.wav
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import wave
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import sys
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from math import pi
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class Fifo(object):
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def __init__(self, size):
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@ -46,16 +47,36 @@ def med_filt_stream(stream, kernel=5):
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accum.append(f)
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yield median(accum.list())
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def dc_filt_stream(stream, kernel=2):
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def dc_filt_stream(stream, kernel=5000):
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accum = Fifo(kernel)
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for f in stream:
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accum.append(f)
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dc = sum(accum.list()) / len(accum.list())
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yield f - dc
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def scale_stream(stream, gamma=1.2, makeup=1000):
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# map x -> scale*x^gamma, but maintain:
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# 0xffff = scale*0xffff^gamma
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scale = makeup * 0xffff / 0xffff**gamma
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for f in stream:
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if f > 0:
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yield scale * f**gamma
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else:
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yield -scale * (-f)**gamma
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def hpf(stream, f_c=0.2):
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# y[i] := α * (y[i-1] + x[i] - x[i-1])
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alpha = 1 / (2*pi*f_c + 1)
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y_prev, x_prev = 0, 0
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for x in stream:
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y = alpha * (y_prev + x - x_prev)
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yield y
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y_prev = y
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def frames_from_samples(itm):
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b = bytearray()
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for sample in itm:
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sample = round(sample)
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sample = (sample + 0x10000) % 0x10000 # counteract Python's signed mod badness
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lsb0 = sample % 0x100
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lsb1 = (sample // 0x100) % 0x100
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@ -71,30 +92,45 @@ def median(samples):
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def stream_to_wav(file_in, file_out):
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# broken
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itm_stream = stream_itm(file_in)
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clean_stream = dc_filt_stream(med_filt_stream(itm_stream))
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#clean_stream = dc_filt_stream(med_filt_stream(itm_stream))
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#clean_stream = dc_filt_stream(itm_stream)
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clean_stream = dc_filt_stream(itm_stream)
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#clean_stream = scale_stream(itm_stream)
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wave_out = wave.open(file_out, 'wb')
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wave_out.setnchannels(1)
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wave_out.setsampwidth(2)
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wave_out.setframerate(1000)
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wave_out.setframerate(2300)
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wave_out.writeframes(frames_from_samples(list(clean_stream)))
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def stream_to_term(file_in):
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stream = dc_filt_stream(med_filt_stream(stream_itm(file_in)))
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#stream = dc_filt_stream(med_filt_stream(stream_itm(file_in)))
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#stream = scale_stream(dc_filt_stream(stream_itm(file_in)))
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stream = scale_stream(hpf(dc_filt_stream(stream_itm(file_in))))
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#stream = stream_itm(file_in)
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for f in stream:
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print(ansi_rgb(color_for_sample(f), '█'), end='')
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def ansi_rgb(color, text):
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r, g, b = color
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#print(color)
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return '\033[38;2;{r};{g};{b}m{text}\033[0m'.format(**locals())
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def color_for_sample(sample):
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r, g, b = 0, 0, 0
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if sample < 0:
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b = int(-sample)
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b = -sample / 0x100
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else:
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r = int(sample)
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#return (128, 0, 0)
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return r, g, b
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r = sample / 0x100
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if b > 0xff:
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g = min(0xff, b / 16)
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b = 0xff
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if r > 0xff:
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g = min(0xff, r / 16)
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r = 0xff
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assert r < 0x100, sample
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assert g < 0x100, sample
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assert b < 0x100, sample
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return int(r), int(g), int(b)
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def main():
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if len(sys.argv) == 3:
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18
src/main.rs
18
src/main.rs
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@ -115,6 +115,7 @@ mod bsp;
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use cortex_m::{iprintln, itm};
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use cortex_m::asm::{bkpt, delay};
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use cortex_m_rt::entry;
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use pdqsort;
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#[entry]
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fn main() -> ! {
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@ -296,7 +297,22 @@ fn main() -> ! {
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// itm::write_all(&mut per.itm.stim[0], &[sample]);
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// }
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loop {
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let sample = (per.adc1.dr.read().bits() << 4) as u16;
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// median filter decimation
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// NB: 3.6 KB/sec for 63 filter width
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// 4.4 KB/sec for 53 filter width
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// 4.6 KB/sec for 51 filter width
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// 5.0 KB/sec for 49 filter width vv--- these rates and below show alias patterns
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// 5.0 KB/sec for 47 filter width
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// 5.0 KB/sec for 31 filter width
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// 5.0 KB/sec for 15 filter width
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// measured: ll /tmp/itm.txt ; sleep 10 ; ll /tmp/itm.txt
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let mut buf = [0; 51];
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for sub_sample in buf.iter_mut() {
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*sub_sample = (per.adc1.dr.read().bits() << 4) as u16;
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}
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pdqsort::sort(&mut buf);
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let sample = buf[25];
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let high = (sample >> 8) as u8;
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let low = (sample & 0xff) as u8;
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itm::write_all(&mut per.itm.stim[0], &[low, high]);
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