Feature: Repeated sending for DIRECT-route packets with echo-cancellation (improves delivery, reduces floods)

docs/cli_commands.md

@@ -485,6 +485,18 @@ This document provides an overview of CLI commands that can be sent to MeshCore
 
 ---
 
+#### View or change the maximum direct-route resend attempts
+**Usage:**
+- `get max.resend`
+- `set max.resend <value>`
+
+**Parameters:**
+- `value`: Maximum number of resend attempts for direct-routed packets (0–3). `0` disables resending entirely.
+
+**Default:** `2`
+
+---
+
 #### View or change the retransmit delay factor for flood traffic
 **Usage:**
 - `get txdelay`

examples/companion_radio/DataStore.cpp

@@ -233,6 +233,7 @@ void DataStore::loadPrefsInt(const char *filename, NodePrefs& _prefs, double& no
     file.read((uint8_t *)&_prefs.rx_boosted_gain, sizeof(_prefs.rx_boosted_gain));         // 89
     file.read((uint8_t *)_prefs.default_scope_name, sizeof(_prefs.default_scope_name));    // 90
     file.read((uint8_t *)_prefs.default_scope_key, sizeof(_prefs.default_scope_key));     // 121
+    file.read((uint8_t *)&_prefs.max_resend_attempts, sizeof(_prefs.max_resend_attempts)); // 137
 
     file.close();
   }
@@ -273,6 +274,7 @@ void DataStore::savePrefs(const NodePrefs& _prefs, double node_lat, double node_
     file.write((uint8_t *)&_prefs.rx_boosted_gain, sizeof(_prefs.rx_boosted_gain));         // 89
     file.write((uint8_t *)_prefs.default_scope_name, sizeof(_prefs.default_scope_name));    // 90
     file.write((uint8_t *)_prefs.default_scope_key, sizeof(_prefs.default_scope_key));     // 121
+    file.write((uint8_t *)&_prefs.max_resend_attempts, sizeof(_prefs.max_resend_attempts)); // 137
 
     file.close();
   }

examples/companion_radio/MyMesh.cpp

@@ -106,6 +106,10 @@
 #define DIRECT_SEND_PERHOP_EXTRA_MILLIS 250
 #define LAZY_CONTACTS_WRITE_DELAY       5000
 
+#ifndef RESEND_INTERFERENCE_MARGIN
+  #define RESEND_INTERFERENCE_MARGIN   12   // dB above noise floor that blocks a resend (non-invasive LBT)
+#endif
+
 #define PUBLIC_GROUP_PSK                "izOH6cXN6mrJ5e26oRXNcg=="
 
 // these are _pushed_ to client app at any time
@@ -265,6 +269,15 @@ bool MyMesh::getCADEnabled() const {
   return true; // hardware CAD before TX (no CLI toggle on companion; enabled by default)
 }
 
+bool MyMesh::isResendChannelActive() {
+  // Non-invasive resend LBT (NO CAD, so RX stays open to overhear the downstream forward
+  // and cancel the resend). Block the resend when a LoRa preamble/header is being received
+  // (often that forward itself) OR the live channel energy is well above the noise floor
+  // (foreign interference). isReceivingPacket()/getCurrentRSSI() are IRQ/register reads.
+  int margin = (int)radio_driver.getCurrentRSSI() - _radio->getNoiseFloor();
+  return radio_driver.isReceivingPacket() || (margin >= RESEND_INTERFERENCE_MARGIN);
+}
+
 int MyMesh::calcRxDelay(float score, uint32_t air_time) const {
   if (_prefs.rx_delay_base <= 0.0f) return 0;
   return (int)((pow(_prefs.rx_delay_base, 0.85f - score) - 1.0) * air_time);
@@ -274,6 +287,7 @@ uint32_t MyMesh::getRetransmitDelay(const mesh::Packet *packet) {
   uint32_t t = (_radio->getEstAirtimeFor(packet->getPathByteLen() + packet->payload_len + 2) * 0.5f);
   return getRNG()->nextInt(0, 5*t + 1);
 }
+
 uint32_t MyMesh::getDirectRetransmitDelay(const mesh::Packet *packet) {
   uint32_t t = (_radio->getEstAirtimeFor(packet->getPathByteLen() + packet->payload_len + 2) * 0.2f);
   return getRNG()->nextInt(0, 5*t + 1);
@@ -881,6 +895,7 @@ MyMesh::MyMesh(mesh::Radio &radio, mesh::RNG &rng, mesh::RTCClock &rtc, SimpleMe
   _prefs.tx_power_dbm = LORA_TX_POWER;
   _prefs.gps_enabled = 0;       // GPS disabled by default
   _prefs.gps_interval = 0;      // No automatic GPS updates by default
+  _prefs.max_resend_attempts = 2;
   //_prefs.rx_delay_base = 10.0f;  enable once new algo fixed
 #if defined(USE_SX1262) || defined(USE_SX1268)
 #ifdef SX126X_RX_BOOSTED_GAIN
@@ -938,6 +953,7 @@ void MyMesh::begin(bool has_display) {
   _prefs.tx_power_dbm = constrain(_prefs.tx_power_dbm, -9, MAX_LORA_TX_POWER);
   _prefs.gps_enabled = constrain(_prefs.gps_enabled, 0, 1);  // Ensure boolean 0 or 1
   _prefs.gps_interval = constrain(_prefs.gps_interval, 0, 86400);  // Max 24 hours
+  _prefs.max_resend_attempts = constrain(_prefs.max_resend_attempts, 0, 3);
 
 #ifdef BLE_PIN_CODE // 123456 by default
   if (_prefs.ble_pin == 0) {
@@ -1440,6 +1456,9 @@ void MyMesh::handleCmdFrame(size_t len) {
         _prefs.advert_loc_policy = cmd_frame[3];
         if (len >= 5) {
           _prefs.multi_acks = cmd_frame[4];
+          if (len >= 6) {
+            _prefs.max_resend_attempts = constrain(cmd_frame[5], 0, 3);
+          }
         }
       }
     }

examples/companion_radio/MyMesh.h

@@ -106,10 +106,12 @@ class MyMesh : public BaseChatMesh, public DataStoreHost {
   float getAirtimeBudgetFactor() const override;
   int getInterferenceThreshold() const override;
   bool getCADEnabled() const override;
+  bool isResendChannelActive() override;
   int calcRxDelay(float score, uint32_t air_time) const override;
   uint32_t getRetransmitDelay(const mesh::Packet *packet) override;
   uint32_t getDirectRetransmitDelay(const mesh::Packet *packet) override;
   uint8_t getExtraAckTransmitCount() const override;
+  uint8_t getMaxResendAttempts() const override { return _prefs.max_resend_attempts; }
   bool filterRecvFloodPacket(mesh::Packet* packet) override;
   bool allowPacketForward(const mesh::Packet* packet) override;
 

examples/companion_radio/NodePrefs.h

@@ -34,4 +34,5 @@ struct NodePrefs {  // persisted to file
   uint8_t autoadd_max_hops;  // 0 = no limit, 1 = direct (0 hops), N = up to N-1 hops (max 64)
   char default_scope_name[31];
   uint8_t default_scope_key[16];
+  uint8_t max_resend_attempts; // 0 = disabled, 1-3, default 2
 };

examples/simple_repeater/MyMesh.cpp

@@ -60,6 +60,10 @@
 
 #define LAZY_CONTACTS_WRITE_DELAY    5000
 
+#ifndef RESEND_INTERFERENCE_MARGIN
+  #define RESEND_INTERFERENCE_MARGIN  12   // dB above noise floor that blocks a resend (non-invasive LBT)
+#endif
+
 void MyMesh::putNeighbour(const mesh::Identity &id, uint32_t timestamp, float snr) {
 #if MAX_NEIGHBOURS // check if neighbours enabled
   // find existing neighbour, else use least recently updated
@@ -549,6 +553,14 @@ uint32_t MyMesh::getDirectRetransmitDelay(const mesh::Packet *packet) {
   return getRNG()->nextInt(0, 5*t + 1);
 }
 
+bool MyMesh::isResendChannelActive() {
+  // Non-invasive resend LBT (NO CAD, so RX stays open to overhear the downstream forward
+  // and cancel the resend). Block when a LoRa preamble/header is being received (often that
+  // forward) OR the live channel energy is well above the noise floor (foreign interference).
+  int margin = (int)radio_driver.getCurrentRSSI() - _radio->getNoiseFloor();
+  return radio_driver.isReceivingPacket() || (margin >= RESEND_INTERFERENCE_MARGIN);
+}
+
 mesh::DispatcherAction MyMesh::onRecvPacket(mesh::Packet* pkt) {
   if (pkt->getRouteType() == ROUTE_TYPE_TRANSPORT_FLOOD) {
     recv_pkt_region = region_map.findMatch(pkt, REGION_DENY_FLOOD);
@@ -877,6 +889,7 @@ MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondCloc
   _prefs.rx_delay_base = 0.0f;   // turn off by default, was 10.0;
   _prefs.tx_delay_factor = 0.5f; // was 0.25f
   _prefs.direct_tx_delay_factor = 0.3f; // was 0.2
+  _prefs.max_resend_attempts = 2;
   StrHelper::strncpy(_prefs.node_name, ADVERT_NAME, sizeof(_prefs.node_name));
   _prefs.node_lat = ADVERT_LAT;
   _prefs.node_lon = ADVERT_LON;

examples/simple_repeater/MyMesh.h

@@ -153,12 +153,16 @@ class MyMesh : public mesh::Mesh, public CommonCLICallbacks {
   bool getCADEnabled() const override {
     return _prefs.cad_enabled;
   }
+  bool isResendChannelActive() override;   // non-invasive resend LBT (preamble/RSSI, no CAD)
   int getAGCResetInterval() const override {
     return ((int)_prefs.agc_reset_interval) * 4000;   // milliseconds
   }
   uint8_t getExtraAckTransmitCount() const override {
     return _prefs.multi_acks;
   }
+  uint8_t getMaxResendAttempts() const override {
+    return _prefs.max_resend_attempts;
+  }
 
 #if ENV_INCLUDE_GPS == 1
   void applyGpsPrefs() {

examples/simple_room_server/MyMesh.cpp

@@ -10,6 +10,10 @@
 
 #define POST_SYNC_DELAY_SECS        6
 
+#ifndef RESEND_INTERFERENCE_MARGIN
+  #define RESEND_INTERFERENCE_MARGIN  12   // dB above noise floor that blocks a resend (non-invasive LBT)
+#endif
+
 #define FIRMWARE_VER_LEVEL       1
 
 #define REQ_TYPE_GET_STATUS         0x01 // same as _GET_STATS
@@ -280,6 +284,14 @@ uint32_t MyMesh::getDirectRetransmitDelay(const mesh::Packet *packet) {
   return getRNG()->nextInt(0, 5*t + 1);
 }
 
+bool MyMesh::isResendChannelActive() {
+  // Non-invasive resend LBT (NO CAD, so RX stays open to overhear the downstream forward
+  // and cancel the resend). Block when a LoRa preamble/header is being received (often that
+  // forward) OR the live channel energy is well above the noise floor (foreign interference).
+  int margin = (int)radio_driver.getCurrentRSSI() - _radio->getNoiseFloor();
+  return radio_driver.isReceivingPacket() || (margin >= RESEND_INTERFERENCE_MARGIN);
+}
+
 bool MyMesh::allowPacketForward(const mesh::Packet *packet) {
   if (_prefs.disable_fwd) return false;
   if (packet->isRouteFlood()) {
@@ -633,6 +645,7 @@ MyMesh::MyMesh(mesh::MainBoard &board, mesh::Radio &radio, mesh::MillisecondCloc
   _prefs.rx_delay_base = 0.0f;   // off by default, was 10.0
   _prefs.tx_delay_factor = 0.5f; // was 0.25f;
   _prefs.direct_tx_delay_factor = 0.2f; // was zero
+  _prefs.max_resend_attempts = 2;
   StrHelper::strncpy(_prefs.node_name, ADVERT_NAME, sizeof(_prefs.node_name));
   _prefs.node_lat = ADVERT_LAT;
   _prefs.node_lon = ADVERT_LON;

examples/simple_room_server/MyMesh.h

@@ -147,12 +147,16 @@ class MyMesh : public mesh::Mesh, public CommonCLICallbacks {
   bool getCADEnabled() const override {
     return _prefs.cad_enabled;
   }
+  bool isResendChannelActive() override;   // non-invasive resend LBT (preamble/RSSI, no CAD)
   int getAGCResetInterval() const override {
     return ((int)_prefs.agc_reset_interval) * 4000;   // milliseconds
   }
   uint8_t getExtraAckTransmitCount() const override {
     return _prefs.multi_acks;
   }
+  uint8_t getMaxResendAttempts() const override {
+    return _prefs.max_resend_attempts;
+  }
 
   mesh::DispatcherAction onRecvPacket(mesh::Packet* pkt) override;
 

examples/simple_sensor/SensorMesh.cpp

@@ -715,6 +715,7 @@ SensorMesh::SensorMesh(mesh::MainBoard& board, mesh::Radio& radio, mesh::Millise
   _prefs.rx_delay_base =   0.0f;  // turn off by default, was 10.0;
   _prefs.tx_delay_factor = 0.5f;   // was 0.25f
   _prefs.direct_tx_delay_factor = 0.2f; // was zero
+  _prefs.max_resend_attempts = 2;
   StrHelper::strncpy(_prefs.node_name, ADVERT_NAME, sizeof(_prefs.node_name));
   _prefs.node_lat = ADVERT_LAT;
   _prefs.node_lon = ADVERT_LON;

examples/simple_sensor/SensorMesh.h

@@ -122,6 +122,7 @@ class SensorMesh : public mesh::Mesh, public CommonCLICallbacks {
   int getInterferenceThreshold() const override;
   bool getCADEnabled() const override;
   int getAGCResetInterval() const override;
+  uint8_t getMaxResendAttempts() const override { return _prefs.max_resend_attempts; }
   void onAnonDataRecv(mesh::Packet* packet, const uint8_t* secret, const mesh::Identity& sender, uint8_t* data, size_t len) override;
   int searchPeersByHash(const uint8_t* hash) override;
   void getPeerSharedSecret(uint8_t* dest_secret, int peer_idx) override;