From 26c23dc8a0444b0d329356e12920654c487146ef Mon Sep 17 00:00:00 2001
From: Jared Boone <jboone@earfeast.com>
Date: Wed, 4 Nov 2015 09:49:14 -0800
Subject: [PATCH] Use new FIR decimation in FSK demodulator.

Reduces FIR calculation effort when output samples are skipped at FIR filter, not after.
---
 firmware/baseband/proc_fsk.cpp | 4 ++--
 firmware/baseband/proc_fsk.hpp | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/firmware/baseband/proc_fsk.cpp b/firmware/baseband/proc_fsk.cpp
index a26c224a..42d6edbd 100644
--- a/firmware/baseband/proc_fsk.cpp
+++ b/firmware/baseband/proc_fsk.cpp
@@ -65,7 +65,7 @@ void FSKProcessor::execute(buffer_c8_t buffer) {
 
 	/* 153.6kHz complex<int16_t>[128]
 	 * -> FIR filter, <?kHz (?fs) pass, gain 1.0
-	 * -> 76.8kHz int16_t[64] */
+	 * -> 19.2kHz int16_t[16] */
 	auto channel = channel_filter.execute(decimator_out, work_baseband_buffer);
 
 	/* 76.8kHz, 64 samples */
@@ -79,7 +79,7 @@ void FSKProcessor::execute(buffer_c8_t buffer) {
 	// 76.8k
 
 	// TODO: Factor out this hidden decimation magic.
-	for(size_t i=0; i<channel.count; i+=4) {
+	for(size_t i=0; i<channel.count; i++) {
 		// TODO: No idea why implicit cast int16_t->float is not allowed.
 		const std::complex<float> sample {
 			static_cast<float>(channel.p[i].real()),
diff --git a/firmware/baseband/proc_fsk.hpp b/firmware/baseband/proc_fsk.hpp
index d2324dc9..72dd09df 100644
--- a/firmware/baseband/proc_fsk.hpp
+++ b/firmware/baseband/proc_fsk.hpp
@@ -55,7 +55,7 @@ private:
 	
 	ChannelDecimator decimator { ChannelDecimator::DecimationFactor::By16 };
 	const fir_taps_real<64>& channel_filter_taps = taps_64_lp_031_070_tfilter;
-	dsp::decimate::FIRAndDecimateComplex channel_filter { channel_filter_taps.taps, 2 };
+	dsp::decimate::FIRAndDecimateComplex channel_filter { channel_filter_taps.taps, 8 };
 
 	dsp::matched_filter::MatchedFilter mf { baseband::ais::rrc_taps_128_decim_4_p, 1 };