From 45a1ccbc53fa951331dd83acd19cca8b7d330b61 Mon Sep 17 00:00:00 2001
From: Jared Boone <jboone@earfeast.com>
Date: Wed, 3 Aug 2016 16:12:01 -0700
Subject: [PATCH] Correctly map TX gain from dB to register value.

---
 firmware/application/max2837.cpp | 16 ++++++++++++++--
 firmware/application/max2837.hpp | 10 +++++++++-
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/firmware/application/max2837.cpp b/firmware/application/max2837.cpp
index 33e4a8b60..4db7bf923 100644
--- a/firmware/application/max2837.cpp
+++ b/firmware/application/max2837.cpp
@@ -55,6 +55,18 @@ static uint_fast8_t gain_ordinal(const int8_t db) {
 
 } /* namespace vga */
 
+namespace tx {
+
+static uint_fast8_t gain_ordinal(const int8_t db) {
+	const auto db_sat = gain_db_range.clip(db);
+	uint8_t value = db_sat & 0x0f;
+	value = (db_sat >= 16) ? (value | 0x20) : value;
+	value = (db_sat >= 32) ? (value | 0x10) : value;
+	return (value & 0b111111) ^ 0b111111;
+}
+
+} /* namespace tx */
+
 namespace filter {
 
 static uint_fast8_t bandwidth_ordinal(const uint32_t bandwidth) {
@@ -170,8 +182,8 @@ reg_t MAX2837::read(const Register reg) {
 	return read(toUType(reg));
 }
 
-void MAX2837::set_tx_vga_gain(const int_fast8_t value) {
-	_map.r.tx_gain.TXVGA_GAIN_SPI = value;
+void MAX2837::set_tx_vga_gain(const int_fast8_t db) {
+	_map.r.tx_gain.TXVGA_GAIN_SPI = tx::gain_ordinal(db);
 	_dirty[Register::TX_GAIN] = 1;
 	flush();
 }
diff --git a/firmware/application/max2837.hpp b/firmware/application/max2837.hpp
index 6c91ae58d..857bb4e9b 100644
--- a/firmware/application/max2837.hpp
+++ b/firmware/application/max2837.hpp
@@ -83,6 +83,14 @@ constexpr int8_t gain_db_step = 2;
 
 /*************************************************************************/
 
+namespace tx {
+
+constexpr range_t<int8_t> gain_db_range { 0, 47 };
+constexpr int8_t gain_db_step = 1;
+}
+
+/*************************************************************************/
+
 namespace filter {
 
 constexpr std::array<uint32_t, 16> bandwidths {
@@ -829,7 +837,7 @@ public:
 	void init();
 	void set_mode(const Mode mode);
 
-	void set_tx_vga_gain(const int_fast8_t value);
+	void set_tx_vga_gain(const int_fast8_t db);
 	void set_lna_gain(const int_fast8_t db);
 	void set_vga_gain(const int_fast8_t db);
 	void set_lpf_rf_bandwidth(const uint32_t bandwidth_minimum);