python: Added curses frequency plot example

2 files changed, 153 insertions, 0 deletions

diff --git a/host/examples/python/CMakeLists.txt b/host/examples/python/CMakeLists.txt
index 4b75f57bd..669c80203 100644
--- a/host/examples/python/CMakeLists.txt
+++ b/host/examples/python/CMakeLists.txt
@@ -7,6 +7,7 @@
 SET(python_examples
     rx_to_file.py
     tx_waveforms.py
+    curses_fft.py
 )
 
 UHD_INSTALL(PROGRAMS ${python_examples} DESTINATION ${PKG_LIB_DIR}/examples/python COMPONENT examples)
diff --git a/host/examples/python/curses_fft.py b/host/examples/python/curses_fft.py
new file mode 100755
index 000000000..7a447cc67
--- /dev/null
+++ b/host/examples/python/curses_fft.py
@@ -0,0 +1,152 @@
+#!/usr/bin/env python
+#
+# Copyright 2017-2018 Ettus Research, a National Instruments Company
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+"""
+Curses FFT example using Python API
+"""
+
+import argparse
+import curses as cs
+import numpy as np
+import uhd
+
+
+def parse_args():
+    """Parse the command line arguments"""
+    parser = argparse.ArgumentParser()
+    parser.add_argument("-a", "--args", default="", type=str)
+    parser.add_argument("-f", "--freq", type=float, required=True)
+    parser.add_argument("-r", "--rate", default=1e6, type=float)
+    parser.add_argument("-g", "--gain", type=int, default=10)
+    parser.add_argument("-c", "--channel", type=int, default=0)
+    parser.add_argument("-n", "--nsamps", type=int, default=100000)
+    parser.add_argument("--dyn", type=int, default=60)
+    parser.add_argument("--ref", type=int, default=0)
+    return parser.parse_args()
+
+
+def psd(nfft, samples):
+    """Return the power spectral density of `samples`"""
+    window = np.hamming(nfft)
+    result = np.multiply(window, samples)
+    result = np.fft.fftshift(np.fft.fft(result, nfft))
+    result = np.square(np.abs(result))
+    result = np.nan_to_num(10.0 * np.log10(result))
+    result = np.abs(result)
+    return result
+
+
+def clip(minval, maxval, value):
+    """Clip the value between a and b"""
+    return min(minval, max(maxval, value))
+
+
+def main():
+    """Create Curses display of FFT"""
+    args = parse_args()
+    usrp = uhd.usrp.MultiUSRP(args.args)
+
+    # Set the USRP rate, freq, and gain
+    usrp.set_rx_rate(args.rate, args.channel)
+    usrp.set_rx_freq(uhd.types.TuneRequest(args.freq), args.channel)
+    usrp.set_rx_gain(args.gain, args.channel)
+
+    # Initialize the curses screen
+    screen = cs.initscr()
+    cs.curs_set(0)
+    cs.noecho()
+    cs.cbreak()
+    screen.keypad(1)
+    height, width = screen.getmaxyx()
+
+    # Create a pad for the y-axis
+    y_axis_width = 10
+    y_axis = cs.newwin(height, y_axis_width, 0, 0)
+
+    # Create the buffer to recv samples
+    num_samps = max(args.nsamps, width)
+    samples = np.empty((1, num_samps), dtype=np.complex64)
+
+    st_args = uhd.usrp.StreamArgs("fc32", "sc16")
+    st_args.channels = [args.channel]
+
+    metadata = uhd.types.RXMetadata()
+    streamer = usrp.get_rx_stream(st_args)
+    buffer_samps = streamer.get_max_num_samps()
+    recv_buffer = np.zeros((1, buffer_samps), dtype=np.complex64)
+
+    stream_cmd = uhd.types.StreamCMD(uhd.types.StreamMode.start_cont)
+    stream_cmd.stream_now = True
+    streamer.issue_stream_cmd(stream_cmd)
+
+    db_step = float(args.dyn) / (height - 1.0)
+    db_start = db_step * int((args.ref - args.dyn) / db_step)
+    db_stop = db_step * int(args.ref / db_step)
+
+    try:
+        while True:
+            # Resize the frequency plot on screen resize
+            screen.clear()
+            if cs.is_term_resized(height, width):
+                height, width = screen.getmaxyx()
+                cs.resizeterm(height, width)
+
+                db_step = float(args.dyn) / (height - 1.0)
+                db_start = db_step * int((args.ref - args.dyn) / db_step)
+                db_stop = db_step * int(args.ref / db_step)
+
+                y_axis.clear()
+
+            # Create the vertical (dBfs) axis
+            y_axis.addstr(0, 1, "{:> 6.2f} |-".format(db_stop))
+            for i in range(1, height - 1):
+                label = db_stop - db_step * i
+                y_axis.addstr(i, 1, "{:> 6.2f} |-".format(label))
+            try:
+                y_axis.addstr(height - 1, 1, "{:> 6.2f} |-".format(db_start))
+            except cs.error:
+                pass
+            y_axis.refresh()
+
+            # Receive the samples
+            recv_samps = 0
+            while recv_samps < num_samps:
+                samps = streamer.recv(recv_buffer, metadata)
+
+                if metadata.error_code != uhd.types.RXMetadataErrorCode.none:
+                    print(metadata.strerror())
+                if samps:
+                    real_samps = min(num_samps - recv_samps, samps)
+                    samples[:, recv_samps:recv_samps + real_samps] = recv_buffer[:, 0:real_samps]
+                    recv_samps += real_samps
+
+            # Get the power in each bin
+            bins = psd(width, samples[args.channel][0:width])
+
+            for i in range(y_axis_width, width):
+                vertical_slot = clip(height, 0, np.int(bins[i] / db_step))
+                try:
+                    for j in range(vertical_slot, height):
+                        screen.addch(j, i, '*')
+                except cs.error:
+                    pass
+            screen.refresh()
+
+    except KeyboardInterrupt:
+        pass
+
+    stream_cmd = uhd.types.StreamCMD(uhd.types.StreamMode.stop_cont)
+    streamer.issue_stream_cmd(stream_cmd)
+
+    cs.curs_set(1)
+    cs.nocbreak()
+    screen.keypad(0)
+    cs.echo()
+    cs.endwin()
+
+
+if __name__ == "__main__":
+    main()