Add analyzer script to produce figures of random bytes distribution.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>

firmware/pico_rng_analyze.py

@@ -0,0 +1,56 @@
+#!/usr/bin/env python3
+
+import numpy as np
+import matplotlib.pyplot as plt
+import argparse
+from scipy import stats
+
+parser = argparse.ArgumentParser(description="Raspberry Pi Pico Random Number Generator Test Analyzer")
+parser.add_argument("file", help="File that contains a random sample of bytes.", metavar="FILENAME")
+args = parser.parse_args()
+
+def read_in_chunks(file_object, chunk_size=1024):
+    """Lazy function (generator) to read a file piece by piece.
+    Default chunk size: 1k."""
+    while True:
+        data = file_object.read(chunk_size)
+        if not data:
+            break
+        yield data
+
+with open(args.file, 'rb') as f:
+    myhist = np.zeros(256, dtype='float64')
+    chisqs = []
+    chisps = []
+    acumd = 0
+    acumn = 0
+    for data in read_in_chunks(f, 10000):
+        n, jnk = np.histogram(list(data), list(range(257)))
+        myhist += n
+        chisq, chisp = stats.chisquare(n)
+        chisqs.append(chisq)
+        chisps.append(chisp*100)
+        acumd += sum(data)
+        acumn += len(data)
+
+#    plt.subplot(1, 2, 1)
+    plt.bar(range(256), myhist/np.sum(myhist), width=1)
+    plt.ylabel('Probability')
+    plt.title(f'Distribution of randomness [$\mu$={acumd/acumn:.4f}]')
+    plt.grid(True)
+    plt.show()
+
+    plt.subplot(1, 2, 1)
+    n, bins, _ = plt.hist(chisqs, 401, density=True)
+    plt.ylabel('Probability')
+    plt.title(f'Distribution of chi-square [$\mu$={np.mean(chisqs):.4f}, Mdn={np.median(chisqs):.4f}]')
+    plt.grid(True)
+
+    plt.subplot(1, 2, 2)
+    n, bins, _ = plt.hist(chisps, list(range(101)), density=False)
+    plt.ylabel('Probability')
+    plt.title(f'Distribution of percentage excess [$\mu$={np.mean(chisps):.4f}, Mdn={np.median(chisps):.4f}]')
+    plt.grid(True)
+    plt.show()
+
+