From 4a374e022dd35f59e34bd6cb0e5192c55b384b00 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20K=C3=A4berich?= <j.kaeberich@gmx.de>
Date: Wed, 15 Sep 2021 18:20:44 +0200
Subject: [PATCH] additional SCPI example for trace data reading

---
 .../UserManual/SCPI_Examples/libreVNA.py      | 17 +++++++
 .../SCPI_Examples/retrieve_trace_data.py      | 49 +++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 Documentation/UserManual/SCPI_Examples/retrieve_trace_data.py

diff --git a/Documentation/UserManual/SCPI_Examples/libreVNA.py b/Documentation/UserManual/SCPI_Examples/libreVNA.py
index 233c3e3..2365b98 100644
--- a/Documentation/UserManual/SCPI_Examples/libreVNA.py
+++ b/Documentation/UserManual/SCPI_Examples/libreVNA.py
@@ -80,3 +80,20 @@ class libreVNA:
         self.sock.sendall(query.encode())
         self.sock.send(b"\n")
         return self.__read_response()
+    
+    @staticmethod
+    def parse_trace_data(data):
+        ret = []
+        # Remove brackets (order of data implicitly known)
+        data = data.replace(']','').replace('[','')
+        values = data.split(',')
+        if int(len(values) / 3) * 3 != len(values):
+            # number of values must be a multiple of three (frequency, real, imaginary)
+            raise Exception("Invalid input data: expected tuples of three values each")
+        for i in range(0, len(values), 3):
+            freq = float(values[i])
+            real = float(values[i+1])
+            imag = float(values[i+2])
+            ret.append((freq, complex(real, imag)))
+        return ret       
+
diff --git a/Documentation/UserManual/SCPI_Examples/retrieve_trace_data.py b/Documentation/UserManual/SCPI_Examples/retrieve_trace_data.py
new file mode 100644
index 0000000..dd043a9
--- /dev/null
+++ b/Documentation/UserManual/SCPI_Examples/retrieve_trace_data.py
@@ -0,0 +1,49 @@
+#!/usr/bin/env python3
+
+import time
+from libreVNA import libreVNA
+
+# Create the control instance
+vna = libreVNA('localhost', 19542)
+
+# Quick connection check (should print "LibreVNA-GUI")
+print(vna.query("*IDN?"))
+
+# Make sure we are connecting to a device (just to be sure, with default settings the LibreVNA-GUI auto-connects)
+vna.cmd(":DEV:CONN")
+dev = vna.query(":DEV:CONN?")
+if dev == "Not connected":
+    print("Not connected to any device, aborting")
+    exit(-1)
+else:
+    print("Connected to "+dev)
+
+# Simple trace data extraction
+
+# switch to VNA mode, setup the sweep parameters
+print("Setting up the sweep...")
+vna.cmd(":DEV:MODE VNA")
+vna.cmd(":VNA:SWEEP FREQUENCY")
+vna.cmd(":VNA:STIM:LVL -10")
+vna.cmd(":VNA:ACQ:IFBW 100")
+vna.cmd(":VNA:ACQ:AVG 1")
+vna.cmd(":VNA:ACQ:POINTS 501")
+vna.cmd(":VNA:FREQuency:START 2000000000")
+vna.cmd(":VNA:FREQuency:STOP 3500000000")
+
+# wait for the sweep to finish
+print("Waiting for the sweep to finish...")
+while vna.query(":VNA:ACQ:FIN?") == "FALSE":
+    time.sleep(0.1)
+
+# grab the data of trace S11
+print("Reading trace data...")
+data = vna.query(":VNA:TRACE:DATA? S11")
+
+# Returned data is just a string containing all the measurement points.
+# Parsing the data returns a list containing frequency/complex tuples
+S11 = vna.parse_trace_data(data)
+
+for x in S11:
+    print(x)
+