Changed:

main.cpp: fixed the “only sends once” bug by replacing last_tx_second with a UTC minute key, so Bob/CY/DAN can send once per active peer every minute at their scheduled second.
TBeamSupremeLoRaInterface.cpp: added RSSI/SNR to receive-side PHY logging, including accepted frames, malformed frames, and simulated PHY drops.
main.cpp: added RSSI/SNR to RX ANNOUNCE and inbound RX LINK establishment logs.
README.md: added updated RSSI/SNR examples and a table for RNSLINKREQ, RNSPROOF_DELAY, RNSPROOF, RNSLRRTT, RNSLINKRX, and RNSDEC.

exercises/205_sustained_link/README.md

@@ -50,10 +50,11 @@ Substantive events retain the Exercise 204 style so multi-unit log parsing can c
 
 ```text
 TX ANNOUNCE: Bob
-RX ANNOUNCE: label=Cy hash=<destination hash> phy=Cy(2)
+RX PHY: phy=2 len=... RSSI=-73.5 SNR=9.2 frames=...
+RX ANNOUNCE: label=Cy hash=<destination hash> phy=Cy(2) RSSI=-73.5 SNR=9.2
 TX LINKREQUEST: opening link to Cy slot=19 attempt=1/3
 LINK ACTIVE: initiator link established to Cy hash=<link hash>
-RX LINK: inbound link established hash=<link hash> phy=Bob(1)
+RX LINK: inbound link established hash=<link hash> phy=Bob(1) RSSI=-74.0 SNR=8.8
 TX LINK: BOB says Hi to CY iter=0 via=outbound hash=<link hash> status=2
 RX LINK: CY says Hi to BOB iter=0 | phy=Cy(2) RSSI=... SNR=...
 LINK RETRY: no establishment after 60000 ms; retrying Cy attempts=1/3
@@ -61,6 +62,19 @@ LINK FAILED: peer=Cy attempts=3 window_ms=... waiting_for_announce=1
 LINK RETRY RESET: fresh announce from Cy
 ```
 
+`RX PHY` is emitted once per accepted LoRa frame before Reticulum decrypts or routes it. It is the broadest signal-strength record and includes frames that become announces, link setup packets, encrypted Link payloads, keepalives, or proofs. `RX PHY BAD` and `SIM PHY DROP` also include RSSI/SNR when malformed or intentionally blocked frames are seen.
+
+The following `RNS...` prefixes are generated by the linked microReticulum tree when Arduino link instrumentation is enabled:
+
+| Prefix | Source | Meaning |
+| --- | --- | --- |
+| `RNSLINKREQ` | `microReticulum/src/Link.cpp` | Incoming Link request validation accepted; shows the new link ID, owner destination, hops, status, initiator flag, interface, and whether the app has a link-established callback. |
+| `RNSPROOF_DELAY` | `microReticulum/src/Link.cpp` | Link proof send path is applying the configured proof delay before transmitting the proof packet. |
+| `RNSPROOF` | `microReticulum/src/Link.cpp` and transport proof probes | Link proof validation and proof forwarding diagnostics, including signature validity, state transitions, interface checks, and exceptions. |
+| `RNSLRRTT` | `microReticulum/src/Link.cpp` | Link request round-trip-time packet handling. This is part of Link establishment and marks decrypt, active, and owner callback events. |
+| `RNSLINKRX` | `microReticulum/src/Link.cpp` | Link-associated packet receive path. It logs packet context, decrypt success, app packet callback entry/return, no-callback cases, and LRRTT dispatch. |
+| `RNSDEC` | `microReticulum/src/Link.cpp` | Link encryption/decryption token diagnostics, including encrypt attempts, decrypt attempts, and decrypt failure class. |
+
 Reticulum library logging is set to warning level in this exercise. Heap, path-store, entries, and byte-count diagnostics are intentionally suppressed so serial logs remain focused on field-test results.
 
 # Build, Upload, And Monitor

exercises/205_sustained_link/src/TBeamSupremeLoRaInterface.cpp

@@ -103,6 +103,12 @@ void TBeamSupremeLoRaInterface::loop() {
       _radio->startReceive();
       return;
     }
+    Serial.printf("RX PHY: phy=%u len=%d RSSI=%.1f SNR=%.1f frames=%lu\r\n",
+                  (unsigned)physical_tx,
+                  len,
+                  _last_rssi,
+                  _last_snr,
+                  (unsigned long)_phy_rx_frames);
     if (len <= 1) {
       _radio->startReceive();
       return;
@@ -158,21 +164,33 @@ bool TBeamSupremeLoRaInterface::unpack_frame(uint8_t* frame, int& len, uint8_t&
 #if SIM_PHY_ENVELOPE
   if (len < PHY_ENVELOPE_LEN + 1) {
     ++_phy_bad_frames;
+    Serial.printf("RX PHY BAD: reason=short len=%d RSSI=%.1f SNR=%.1f bad=%lu\r\n",
+                  len,
+                  _last_rssi,
+                  _last_snr,
+                  (unsigned long)_phy_bad_frames);
     DEBUGF("SIM PHY malformed: short frame len=%d", len);
     return false;
   }
   if (frame[0] != PHY_MAGIC_0 || frame[1] != PHY_MAGIC_1 || frame[2] != PHY_VERSION) {
     ++_phy_bad_frames;
+    Serial.printf("RX PHY BAD: reason=envelope len=%d RSSI=%.1f SNR=%.1f bad=%lu\r\n",
+                  len,
+                  _last_rssi,
+                  _last_snr,
+                  (unsigned long)_phy_bad_frames);
     DEBUGF("SIM PHY malformed: bad envelope len=%d", len);
     return false;
   }
   physical_tx = frame[3];
   if (should_drop_physical_tx(physical_tx)) {
     ++_phy_blocked_frames;
-    Serial.printf("SIM PHY DROP: rx=%u tx=%u len=%d blocked=%lu\r\n",
+    Serial.printf("SIM PHY DROP: rx=%u tx=%u len=%d RSSI=%.1f SNR=%.1f blocked=%lu\r\n",
                   (unsigned)NODE_SLOT_INDEX,
                   (unsigned)physical_tx,
                   len,
+                  _last_rssi,
+                  _last_snr,
                   (unsigned long)_phy_blocked_frames);
     DEBUGF("SIM PHY DROP: rx=%u tx=%u len=%d",
            (unsigned)NODE_SLOT_INDEX,

exercises/205_sustained_link/src/main.cpp

@@ -123,7 +123,7 @@ struct PeerState {
   uint32_t last_rx_ms = 0;
   uint32_t last_tx_ms = 0;
   uint32_t tx_iter = 0;
-  uint8_t last_tx_second = 255;
+  uint32_t last_tx_minute = 0xFFFFFFFFUL;
 };
 
 static PeerState peers[MAX_PEERS];
@@ -714,7 +714,7 @@ static void clear_peer_slot(uint8_t index) {
   peers[index].last_rx_ms = 0;
   peers[index].last_tx_ms = 0;
   peers[index].tx_iter = 0;
-  peers[index].last_tx_second = 255;
+  peers[index].last_tx_minute = 0xFFFFFFFFUL;
 }
 
 static int ensure_peer_for_label(const String& label) {
@@ -893,10 +893,14 @@ static void on_inbound_link_established(RNS::Link& link) {
     peers[peer_index].last_link_active_ms = millis();
   }
   uint8_t physical_tx = lora_impl ? lora_impl->last_physical_tx() : 255;
-  Serial.printf("RX LINK: inbound link established hash=%s phy=%s(%u)\r\n",
+  float rssi = lora_impl ? lora_impl->last_rssi() : 0.0f;
+  float snr = lora_impl ? lora_impl->last_snr() : 0.0f;
+  Serial.printf("RX LINK: inbound link established hash=%s phy=%s(%u) RSSI=%.1f SNR=%.1f\r\n",
                 link.hash().toHex().c_str(),
                 node_label_for_slot(physical_tx),
-                (unsigned)physical_tx);
+                (unsigned)physical_tx,
+                rssi,
+                snr);
   show_status("LINK ACTIVE", "inbound", link.hash().toHex().c_str());
 }
 
@@ -941,11 +945,15 @@ class LinkAnnounceHandler : public RNS::AnnounceHandler {
     }
 
     uint8_t physical_tx = lora_impl ? lora_impl->last_physical_tx() : 255;
-    Serial.printf("RX ANNOUNCE: label=%s hash=%s phy=%s(%u)\r\n",
+    float rssi = lora_impl ? lora_impl->last_rssi() : 0.0f;
+    float snr = lora_impl ? lora_impl->last_snr() : 0.0f;
+    Serial.printf("RX ANNOUNCE: label=%s hash=%s phy=%s(%u) RSSI=%.1f SNR=%.1f\r\n",
                   peers[peer_index].label.c_str(),
                   peers[peer_index].destination_hash.toHex().c_str(),
                   node_label_for_slot(physical_tx),
-                  (unsigned)physical_tx);
+                  (unsigned)physical_tx,
+                  rssi,
+                  snr);
     show_status("RX ANNOUNCE", peers[peer_index].label.c_str(), peers[peer_index].destination_hash.toHex().c_str());
   }
 };
@@ -1224,9 +1232,10 @@ void loop() {
   maybe_send_scheduled_announce();
   const uint8_t send_slot = node_send_slot_second();
   if (have_rtc_now && rtc_now.second == send_slot) {
+    const uint32_t tx_minute = (uint32_t)(to_epoch_seconds(rtc_now) / 60LL);
     for (uint8_t i = 0; i < MAX_PEERS; ++i) {
       PeerState& peer = peers[i];
-      if (peer.label.length() == 0 || peer.last_tx_second == rtc_now.second) {
+      if (peer.label.length() == 0 || peer.last_tx_minute == tx_minute) {
         continue;
       }
 
@@ -1242,7 +1251,7 @@ void loop() {
         continue;
       }
 
-      peer.last_tx_second = rtc_now.second;
+      peer.last_tx_minute = tx_minute;
       peer.last_tx_ms = now;
       const char* recipient = board_id_for_label(peer.label);
       String message = String(BOARD_ID) + " says Hi to " + recipient + " iter=" + String(peer.tx_iter++);