Fig: WR clocks and PPS

figures/white-rabbit/src/wr-clocks.py

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+#!/usr/bin/env python3
+
+__doc__ = \
+"""Generate some figures showing the alignment of clocks
+in a White Rabbit system with GrandMaster setup.
+"""
+
+import matplotlib.pyplot as plt
+import numpy as np
+import scipy.signal as sig
+rng = np.random.default_rng(12345)
+
+### Functions
+def pps(t, t_start, width=0.5):
+    """
+    Generate a PPS with width $width$ and starting at $t_start.
+    """
+
+    return (t > t_start) & (t < t_start + width)
+
+
+def detect_rising_edges(threshold, data):
+    """
+    Detect rising edges in data.
+
+    https://stackoverflow.com/a/50365462
+    """
+    return np.flatnonzero((data[:-1] < threshold) & (data[1:] > threshold))+1
+
+
+
+def first_shared_edge(x1, x2, threshold=0.3):
+    try:
+        length = len(x2)
+    except TypeError:
+        length = 1
+
+    x1_edges = detect_rising_edges(threshold, x1)
+    if length > 1:
+            x2_edges = detect_rising_edges(threshold, x2)
+    else:
+        x2_edges = x2
+
+    start_edge = x1_edges[x1_edges > x2_edges][0]
+
+    return start_edge
+
+
+def aligned_pps(t, clock_in, pps_in, width=None):
+    t_start = t[first_shared_edge(clock_in, pps_in)]
+
+    if width is not None:
+        return pps(t, t_start, width)
+    else:
+        return pps(t, t_start)
+
+## Main
+def main(time_base = 10e-9):
+    """
+    Generate a figure showing the required GrandMaster inputs
+    with an aligned PPS out and DIO clock,
+    and a random input event and its timestamp.
+    """
+
+    clock_freq = 10e6 # Hz
+    dio_freq = 12.5*clock_freq # Hz
+    
+    pps_in_early = -1.7/clock_freq #s
+    pps_in_width = 10e1/clock_freq #s
+    pps_out_width = 10e1/clock_freq #s
+    
+    t = np.linspace(-2.25*1/clock_freq, 0.8*1/clock_freq, 5000) #
+    
+    random_event_idx = rng.integers(len(t)*2/3, len(t)) # Somewhere within the time space
+    random_event = t[random_event_idx]
+    
+    
+    ## Create Grandmaster input signals
+    clock_in = (sig.square(2*np.pi*clock_freq*t)+1)/2
+    pps_in = pps(t, pps_in_early, pps_in_width)
+    
+    ## Determine output signal
+    clock_alignment = t[first_shared_edge(clock_in, pps_in)]
+    pps_out = aligned_pps(t, clock_in, pps_in, width=pps_out_width)
+    dio = (sig.square(2*np.pi*dio_freq*(t - clock_alignment))+1)/2
+    
+    ## Random event timestamp
+    timestamped_event = t[first_shared_edge(dio, random_event_idx)]
+    
+    # Create the figure
+    fig, axs = plt.subplots(4,1, sharex=True, gridspec_kw={'hspace': 0}, figsize=(16,4))
+    
+    ## Plot signals
+    i=0
+    axs[i].set_ylabel("$\mathrm{PPS}_\mathrm{in}$", rotation='horizontal', ha='right', va='center')
+    axs[i].plot(t, pps_in, 'purple', label="PPS in")
+    
+    i+=1
+    axs[i].set_ylabel("GM Clock\n($10\,\mathrm{MHz}$)", rotation='horizontal', ha='right', va='center')
+    axs[i].plot(t, clock_in, label='10MHz in')
+    
+    i+=1
+    axs[i].set_ylabel("FMC DIO\n($125\,MHz$)", rotation='horizontal', ha='right', va='center')
+    axs[i].plot(t, dio, 'y', label='DIO')
+    axs[i].plot(random_event, 0.5, 'r*')
+    axs[i].axvline(timestamped_event, color='b')
+    
+    i+=1
+    axs[i].set_ylabel("$\mathrm{PPS}_\mathrm{out}$", rotation='horizontal', ha='right', va='center')
+    axs[i].plot(t, pps_out, 'g', label="PPS out")
+    
+    
+    ## Styling
+    for ax in axs:
+        ax.axvline(clock_alignment, color='r', linestyle='--')
+        ax.set_ylim(-0.2, 1.2)
+        ax.set_yticks([])
+        ax.set_yticklabels([])
+        ax.grid()
+
+    if time_base == 10e-9:
+        axs[-1].set_xlabel("Time (ns)")
+    
+        ticks = axs[-1].get_xticks()/time_base
+        axs[-1].set_xticklabels(np.floor(ticks))
+    else:
+        axs[-1].set_xlabel("Time (s)")
+
+    return fig, (clock_alignment, random_event, timestamped_event)
+
+if __name__ == "__main__":
+    from argparse import ArgumentParser
+    import os.path as path
+
+    parser = ArgumentParser(description=__doc__)
+    parser.add_argument("fname", metavar="path/to/figure[/]", nargs="?", help="Location for generated figure, will append __file__ if a directory. If not supplied, figure is shown.")
+
+    args = parser.parse_args()
+
+    if args.fname is not None and path.isdir(args.fname):
+        args.fname = path.join(args.fname, path.splitext(path.basename(__file__))[0] + ".pdf")
+
+    ###
+    fig, _ = main()
+
+    if args.fname is not None:
+        plt.savefig(args.fname)
+    else:
+        plt.show()
+