From 8e6e1d62ef9beb978879bfd156b3ff51940c8725 Mon Sep 17 00:00:00 2001
From: Nao Pross <np@0hm.ch>
Date: Thu, 2 Dec 2021 12:50:55 +0100
Subject: Implement phase correction in test file with embedded python block

---
 tests/correlator/epy_block_0.py | 75 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 tests/correlator/epy_block_0.py

(limited to 'tests/correlator/epy_block_0.py')

diff --git a/tests/correlator/epy_block_0.py b/tests/correlator/epy_block_0.py
new file mode 100644
index 0000000..1fa4794
--- /dev/null
+++ b/tests/correlator/epy_block_0.py
@@ -0,0 +1,75 @@
+import pmt
+
+import numpy as np
+from gnuradio import gr
+
+
+class blk(gr.sync_block):
+    def __init__(self):
+        gr.sync_block.__init__(
+            self,
+            name='Phase Lock',
+            in_sig=[np.complex64],
+            out_sig=[np.complex64]
+        )
+
+        # keep track of how many samples were processed,
+        # because tags have an absolute offset
+        self.sampnr: np.complex64 = 0
+
+        # because of block processing a tagged block could
+        # be split in half so we need to keep track of the
+        # "previous" values
+        self.last_phase = 0
+
+    def work(self, input_items, output_items):
+        # TODO: interpolate phase values for frequency correction
+
+        out = output_items[0]
+        inp = input_items[0]
+
+        # create a phase correction vector
+        phase = np.zeros(len(inp), dtype=np.float64)
+
+        # read tags
+        tags = self.get_tags_in_window(0, 0, len(inp))
+
+        # get only phase tags
+        is_phase = lambda tag: pmt.to_python(tag.key) == "phase_est"
+        phase_tags = list(filter(is_phase, tags))
+
+        print(f"Processing {len(inp)} samples, with {len(phase_tags)} tags")
+
+        # compute correction from previous block
+        first_tag = phase_tags[0]
+        first_idx = first_tag.offset - self.sampnr
+        phase[:first_idx] = self.last_phase
+
+        # iterate phase tags "in the middle"
+        for prev_tag, next_tag in zip(phase_tags, phase_tags[1:]):
+            # unpack pmt values
+            pval = pmt.to_python(prev_tag.value)
+
+            # compute indexes in phase vector
+            pidx = prev_tag.offset - self.sampnr
+            idx = next_tag.offset - self.sampnr
+
+            # compute phase correction for block
+            phase[pidx:idx] = pval
+            print(f"Correction for block {pidx} to {idx} is {pval}")
+
+        # compute the remaining part of the block
+        last_tag = phase_tags[-1]
+        last_val = pmt.to_python(last_tag.value)
+        last_idx = last_tag.offset - self.sampnr
+
+        phase[last_idx:] = last_val
+
+        # save values for next call
+        self.last_phase = last_val
+
+        # mark samples as processed and compute to output
+        self.sampnr += len(inp)
+        out[:] = inp * np.exp(-1j * phase)
+
+        return len(out)
-- 
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