Added setSeqnoUp and getSessionKeys

These functions are useful when you have a way to store configuration
on the node. You can use them to avoid joining on restart and to ensure
that sequence numbers are monotonic.

Author: frankleonrose

examples/ttn-otaa/ttn-otaa.ino

@@ -87,7 +87,29 @@ void onEvent (ev_t ev) {
             break;
         case EV_JOINED:
             Serial.println(F("EV_JOINED"));
-
+            {
+              u4_t netid = 0;
+              devaddr_t devaddr = 0;
+              u1_t nwkKey[16];
+              u1_t artKey[16];
+              LMIC_getSessionKeys(&netid, &devaddr, nwkKey, artKey);
+              Serial.print("netid: ");
+              Serial.println(netid, DEC);
+              Serial.print("devaddr: ");
+              Serial.println(devaddr, HEX);
+              Serial.print("artKey: ");
+              for (int i=0; i<sizeof(artKey); ++i) {
+                Serial.print(artKey[i], HEX);
+              }
+              Serial.println("");
+              Serial.print("nwkKey: ");
+              for (int i=0; i<sizeof(nwkKey); ++i) {
+                Serial.print(nwkKey[i], HEX);
+              }
+              Serial.println("");
+
+              LMIC_setSeqnoUp(140);
+            }
             // Disable link check validation (automatically enabled
             // during join, but not supported by TTN at this time).
             LMIC_setLinkCheckMode(0);

src/lmic/lmic.c

@@ -2364,10 +2364,29 @@ void LMIC_setClockError(u2_t error) {
     LMIC.clockError = error;
 }
 
-// \brief return the current uplink sequence number.
+// \brief return the uplink sequence number for the next transmission.
 // This simple getter returns the uplink sequence number maintained by the LMIC engine.
-// It's useful in debugging, as it allows you to correlate a debug trace event with
+// The caller should store the value and restore it (see LMIC_setSeqnoUp) on
+// LMIC initialization to ensure monotonically increasing sequence numbers.
+// It's also useful in debugging, as it allows you to correlate a debug trace event with
 // a specific packet sent over the air.
 u4_t LMIC_getSeqnoUp(void) {
     return LMIC.seqnoUp;
 }
+
+// \brief set the uplink sequence number for the next transmission.
+// Use the function on startup to ensure that the next transmission uses
+// a sequence number higher than the last transmission.
+u4_t LMIC_setSeqnoUp(u4_t seq_no) {
+    u4_t last = LMIC.seqnoUp;
+    LMIC.seqnoUp = seq_no;
+    return last;
+}
+
+// \brief return the current session keys returned from join.
+void LMIC_getSessionKeys (u4_t *netid, devaddr_t *devaddr, xref2u1_t nwkKey, xref2u1_t artKey) {
+    *netid = LMIC.netid;
+    *devaddr = LMIC.devaddr;
+    memcpy(artKey, LMIC.artKey, sizeof(LMIC.artKey));
+    memcpy(nwkKey, LMIC.nwkKey, sizeof(LMIC.nwkKey));
+}

src/lmic/lmic.h

@@ -307,6 +307,8 @@ void LMIC_setLinkCheckMode (bit_t enabled);
 void LMIC_setClockError(u2_t error);
 
 u4_t LMIC_getSeqnoUp	(void);
+u4_t LMIC_setSeqnoUp	(u4_t);
+void LMIC_getSessionKeys (u4_t *netid, devaddr_t *devaddr, xref2u1_t nwkKey, xref2u1_t artKey);
 
 // Declare onEvent() function, to make sure any definition will have the
 // C conventions, even when in a C++ file.