From 7dd0070d468bcf5cce7a2abe32a39fff055e43f7 Mon Sep 17 00:00:00 2001
From: drowe67 <drowe67@01035d8c-6547-0410-b346-abe4f91aad63>
Date: Wed, 14 Oct 2015 01:53:47 +0000
Subject: [PATCH] added clock offset ppm measurement software

git-svn-id: https://svn.code.sf.net/p/freetel/code@2440 01035d8c-6547-0410-b346-abe4f91aad63
---
 codec2-dev/octave/fsk_horus.m        | 27 ++++++++++++++++++++++++---
 codec2-dev/octave/fsk_horus_stream.m |  2 +-
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/codec2-dev/octave/fsk_horus.m b/codec2-dev/octave/fsk_horus.m
index d076e194..2a8f5a18 100644
--- a/codec2-dev/octave/fsk_horus.m
+++ b/codec2-dev/octave/fsk_horus.m
@@ -65,6 +65,8 @@ function states = fsk_horus_init()
   states.df = 0;
   states.f1 = 0;
   states.f2 = 0;
+  states.norm_rx_timing = 0;
+  states.ppm = 0;
 endfunction
 
 
@@ -218,8 +220,21 @@ function [rx_bits states] = fsk_horus_demod(states, sf)
 
   states.x = x;
   states.rx_timing = rx_timing;
+  prev_norm_rx_timing = states.norm_rx_timing;
   states.norm_rx_timing = norm_rx_timing;
 
+  % estimate sample clock offset in ppm
+  % d_norm_timing is fraction of symbol period shift over nsym symbols
+
+  d_norm_rx_timing = norm_rx_timing - prev_norm_rx_timing;
+
+  % filter out big jumps due to nin changes
+
+  if abs(d_norm_rx_timing) < 0.1
+    appm = 1E6*d_norm_rx_timing/nsym;
+    states.ppm = 0.9*states.ppm + 0.1*appm;
+  end
+
   % work out how many input samples we need on the next call. The aim
   % is to keep angle(x) away from the -pi/pi (+/- 0.5 fine timing
   % offset) discontinuity.  The side effect is to track sample clock
@@ -492,6 +507,7 @@ function rx_bits_log = demod_file(filename)
   f1_int_resample_log = [];
   f2_int_resample_log = [];
   EbNodB_log = [];
+  ppm_log = [];
 
   % First extract raw bits from samples ------------------------------------------------------
 
@@ -514,6 +530,7 @@ function rx_bits_log = demod_file(filename)
     f1_int_resample_log = [f1_int_resample_log abs(states.f1_int_resample)];
     f2_int_resample_log = [f2_int_resample_log abs(states.f2_int_resample)];
     EbNodB_log = [EbNodB_log states.EbNodB];
+    ppm_log = [ppm_log states.ppm];
   end
 
   printf("plotting...\n");
@@ -535,13 +552,17 @@ function rx_bits_log = demod_file(filename)
   clf
   plot(EbNodB_log);
   title('Eb/No estimate')
-  mean(EbNodB_log)
 
   figure(4)
   clf
   plot(rx);
   title('input signal to demod')
 
+  figure(6);
+  clf
+  plot(ppm_log)
+  title('Sample clock (baud rate) offset in PPM');
+
   printf("frame sync and data extraction...\n");
 
   % Now perform frame sync and extract ASCII text -------------------------------------------
@@ -594,8 +615,8 @@ endfunction
 % run test functions from here during development
 
 %run_sim
-%rx_bits = demod_file("~/Desktop/vk5arg-3.wav");
-%rx_bits = demod_file("~/Desktop/fsk_horus_10dB_1000ppm.wav");
+%rx_bits = demod_file("~/Desktop/vk5arg-3-1.wav");
+rx_bits = demod_file("~/Desktop/fsk_horus_10dB_1000ppm.wav");
 %rx_bits = demod_file("~/Desktop/fsk_horus_6dB_0ppm.wav");
 %rx_bits = demod_file("fsk_horus_rx.raw");
 %rx_bits = demod_file("~/Desktop/fsk_horus_20dB_0ppm_20dBfade.wav");
diff --git a/codec2-dev/octave/fsk_horus_stream.m b/codec2-dev/octave/fsk_horus_stream.m
index 6e94c28e..d6724a9e 100644
--- a/codec2-dev/octave/fsk_horus_stream.m
+++ b/codec2-dev/octave/fsk_horus_stream.m
@@ -49,7 +49,7 @@ while c
     %printf("nin: %d length(rx): %d length(rx_bits_buf): %d \n", nin, length(rx), length(rx_bits_buf));
   endwhile
   f = (states.f1+states.f2)/2; shift = states.f2 - states.f1;
-  printf("max: %d f: %d fshift %d Eb/No: %3.1f SNR: %3.1f bits: %d\r", max(s), f, shift, EbNo, SNR, length(rx_bits_buf));
+  printf("max: %d f: %d fshift %d ppm: %d Eb/No: %3.1f SNR: %3.1f bits: %d\r", max(s), f, shift, states.ppm, EbNo, SNR, length(rx_bits_buf));
 
   % look for complete Horus frame, delimited by 2 unique words
 
-- 
2.25.1