First commit

xfer_tracer/script.py

@@ -0,0 +1,95 @@
+#!/usr/bin/env python3
+
+import pyvisa
+import time
+
+import pyaudio as pa
+import numpy as np
+
+phase = 0.0 # in cycles
+scaled_frequency = 0.0
+# actual frequency = scaled_frequency * sample_rate
+# For repeatability, scaled_frequency should ideally fit in
+# much fewer than 53 bits.
+# More precisely, if scaled_frequency * frame_count is always exact, we get
+# negligible phase errors over 1hr.
+
+def audio_callback(in_data, frame_count, time_info, status):
+	global phase
+	L = np.sin(2 * np.pi * (phase + np.arange(frame_count) * scaled_frequency)).astype(np.float32) # cast to float
+	delta_phase  = scaled_frequency * frame_count # exact
+	delta_phase -= np.floor(delta_phase) # exact
+	phase += delta_phase # error at most ulp(1) = 2^-52
+	if(phase >= 1):
+		phase -= int(phase)
+	outbytes = L.tobytes()
+	#print(L, frame_count)
+	return (outbytes, pa.paContinue)
+
+paudio = pa.PyAudio()
+stream = paudio.open(format=pa.paFloat32,
+	channels=1,
+	rate=48000,
+	output=True,
+	stream_callback=audio_callback)
+
+def do_frequency(scaled_f, osci, hscale):
+	scaled_frequency = scaled_f
+	time.sleep(0.1)
+	osci.write("acquire:state run") # Restart acquisition sequence
+	time.sleep(10 * hscale)
+
+	osci.write("data:source CH1")
+	A_samps = osci.query_binary_values("curve?",datatype='b',container=numpy.array)
+	A_samps = A_samps.astype(np.float64)
+
+	osci.write("data:source CH2") # For now, do not adjust for zeros in the resp.
+	B_samps = osci.query_binary_values("curve?",datatype='b',container=numpy.array)
+	B_samps = B_samps.astype(np.float64)
+
+	A_samps = np.rfft(A_samps) # No window, because of the precise frequency
+	B_samps = np.rfft(B_samps)
+
+	# We have (10 * hscale)/Tcurv periods
+	return B_samps[np.round((10 * hscale) * (scaled_f * 4800))]
+        /A_samps[np.round((10 * hscale) * (scaled_f * 4800))]
+
+def find_oscillo():
+	rm = pyvisa.ResourceManager()
+	R = rm.list_resources("USB?*")
+	if R.empty():
+		print("No device found")
+		exit(1)
+	return rm.open_resource(R[0])
+
+osci = find_oscillo()
+print(osci.query("*IDN?"))
+
+osci.write("*RST")
+time.sleep(5)
+osci.write("horizontal:main:scale 5.0e-4")
+
+osci.write("ch1:scale 1.0e-1")
+osci.write("ch1:bandwidth ON")
+osci.write("ch1:coupling AC")
+osci.write("select:ch1 1")
+
+osci.write("ch2:scale 5.0e-2")
+osci.write("ch2:bandwidth ON")
+osci.write("ch2:coupling AC")
+osci.write("select:ch2 1")
+
+# 8-bit data
+osci.write("data:source CH1")
+osci.write("data:encdg ascii")
+
+osci.write("trigger:main:edge:source CH1")
+osci.write("trigger:main:mode NORMAL")
+osci.write("trigger:main:type EDGE")
+
+osci.write("acquire:mode average")
+osci.write("acquire:numavg 128")
+osci.write("acquire:stopafter sequence")
+osci.write("acquire:state RUN")
+
+print(osci.query("curve?"))

xfer_tracer/shell.nix

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+let
+	pkgs = import <nixpkgs> {};
+in
+pkgs.mkShell {
+	packages = [
+		(pkgs.python3.withPackages (ps : [
+			ps.pyvisa
+			ps.pyvisa-py
+			ps.zeroconf
+			ps.psutil
+			ps.pyusb
+			ps.numpy
+			ps.pyaudio]))
+	];
+}