From e7be7c5121d21413b4c343af5084e10d2736d7bd Mon Sep 17 00:00:00 2001
From: Jared Boone <jboone@earfeast.com>
Date: Sat, 2 Jan 2016 10:49:37 -0800
Subject: [PATCH] Comments about IFIR filter taps design parameters.

---
 firmware/baseband/dsp_fir_taps.hpp | 2 ++
 firmware/baseband/proc_tpms.cpp    | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/firmware/baseband/dsp_fir_taps.hpp b/firmware/baseband/dsp_fir_taps.hpp
index 8b7b6feac..c043cab93 100644
--- a/firmware/baseband/dsp_fir_taps.hpp
+++ b/firmware/baseband/dsp_fir_taps.hpp
@@ -184,6 +184,7 @@ constexpr fir_taps_real<32> taps_6k0_channel {
 
 // WFM 200KF8E emission type //////////////////////////////////////////////
 
+// IFIR image-reject filter: fs=3072000, pass=100000, stop=484000, decim=4, fout=768000
 constexpr fir_taps_real<24> taps_200k_wfm_decim_0 = {
 	.pass_frequency_normalized = 100000.0f / 3072000.0f,
 	.stop_frequency_normalized = 484000.0f / 3072000.0f,
@@ -194,6 +195,7 @@ constexpr fir_taps_real<24> taps_200k_wfm_decim_0 = {
 	} },
 };
 
+// IFIR prototype filter: fs=768000, pass=100000, stop=284000, decim=2, fout=384000
 constexpr fir_taps_real<16> taps_200k_wfm_decim_1 = {
 	.pass_frequency_normalized = 100000.0f / 768000.0f,
 	.stop_frequency_normalized = 284000.0f / 768000.0f,
diff --git a/firmware/baseband/proc_tpms.cpp b/firmware/baseband/proc_tpms.cpp
index 1e8d378a0..e7f8257a8 100644
--- a/firmware/baseband/proc_tpms.cpp
+++ b/firmware/baseband/proc_tpms.cpp
@@ -28,6 +28,7 @@ using namespace lpc43xx;
 
 #include "dsp_fir_taps.hpp"
 
+// IFIR image-reject filter: fs=2457600, pass=100000, stop=407200, decim=4, fout=614400
 static constexpr fir_taps_real<24> taps_200k_decim_0 = {
 	.pass_frequency_normalized = 100000.0f / 2457600.0f,
 	.stop_frequency_normalized = 407200.0f / 2457600.0f,
@@ -38,6 +39,7 @@ static constexpr fir_taps_real<24> taps_200k_decim_0 = {
 	} },
 };
 
+// IFIR prototype filter: fs=614400, pass=100000, stop=207200, decim=2, fout=307200
 static constexpr fir_taps_real<16> taps_200k_decim_1 = {
 	.pass_frequency_normalized = 100000.0f / 614400.0f,
 	.stop_frequency_normalized = 207200.0f / 614400.0f,