New approach to support RX-only mode more cleanly (#2908)

* Add enabled checks in ReceiverModel and TransmitterModel

* Move TX limit logic to TransmitterModel from radio API

* Add TX disable functionality and UI

firmware/application/transmitter_model.cpp

@@ -31,6 +31,8 @@
 #include "portapack_persistent_memory.hpp"
 #include "radio.hpp"
 
+#include <algorithm>
+
 using namespace hackrf::one;
 using namespace portapack;
 
@@ -70,7 +72,7 @@ void TransmitterModel::set_channel_bandwidth(uint32_t v) {
 }
 
 uint8_t TransmitterModel::tx_gain() const {
-    return settings_.tx_gain_db;
+    return std::min(settings_.tx_gain_db, portapack::persistent_memory::config_tx_gain_max_db());
 }
 
 void TransmitterModel::set_tx_gain(uint8_t v_db) {
@@ -79,7 +81,7 @@ void TransmitterModel::set_tx_gain(uint8_t v_db) {
 }
 
 bool TransmitterModel::rf_amp() const {
-    return settings_.rf_amp;
+    return settings_.rf_amp && !portapack::persistent_memory::config_tx_amp_disabled();
 }
 
 void TransmitterModel::set_rf_amp(bool enabled) {
@@ -92,6 +94,15 @@ void TransmitterModel::set_antenna_bias() {
 }
 
 void TransmitterModel::enable() {
+    if (portapack::persistent_memory::config_tx_disabled()) {
+        radio::disable();
+
+        TXDisabledMessage message;
+        EventDispatcher::send_message(message);
+
+        return;
+    }
+
     enabled_ = true;
     radio::set_direction(rf::Direction::Transmit);
     update_tuning_frequency();
@@ -133,11 +144,13 @@ void TransmitterModel::configure_from_app_settings(
 }
 
 void TransmitterModel::update_tuning_frequency() {
-    radio::set_tuning_frequency(target_frequency());
+    if (enabled_)
+        radio::set_tuning_frequency(target_frequency());
 }
 
 void TransmitterModel::update_baseband_bandwidth() {
-    radio::set_baseband_filter_bandwidth_tx(baseband_bandwidth());
+    if (enabled_)
+        radio::set_baseband_filter_bandwidth_tx(baseband_bandwidth());
 }
 
 void TransmitterModel::update_sampling_rate() {
@@ -146,17 +159,20 @@ void TransmitterModel::update_sampling_rate() {
     // protocols that need quick RX/TX turn-around.
 
     // Disabling baseband while changing sampling rates seems like a good idea...
+    if (enabled_)
+        radio::set_baseband_rate(sampling_rate());
 
-    radio::set_baseband_rate(sampling_rate());
     update_tuning_frequency();
 }
 
 void TransmitterModel::update_tx_gain() {
-    radio::set_tx_gain(tx_gain());
+    if (enabled_)
+        radio::set_tx_gain(tx_gain());
 }
 
 void TransmitterModel::update_rf_amp() {
-    radio::set_rf_amp(rf_amp());
+    if (enabled_)
+        radio::set_rf_amp(rf_amp());
 }
 
 void TransmitterModel::update_antenna_bias() {