Enhance checkConnection() function (#240)

* Modify checkConnection()

- Define MESH_CONNECTION_CHECK_ATTEMPTS
- Return from checkConnection() if -2 received, retry if -1, success if address matches, fail otherwise

* Update RF24Mesh_config.h

Co-authored-by: Brendan <[email protected]>

* Remove breaks; from switch

- Per @2bndy5 in #240

* Update comment

---------

Co-authored-by: Brendan <[email protected]>

RF24Mesh.cpp

@@ -159,12 +159,21 @@ template<class network_t, class radio_t>
 bool ESBMesh<network_t, radio_t>::checkConnection()
 {
     // getAddress() doesn't use auto-ack; do a double-check to manually retry 1 more time
-    if (getAddress(_nodeID) < 1) {
-        if (getAddress(_nodeID) < 1) {
-            return false;
+    for (uint8_t i = 0; i < MESH_CONNECTION_CHECK_ATTEMPTS; i++) {
+
+        int16_t result = getAddress(_nodeID);
+        switch (result) {
+            case -2: return false; // Address not found in list or is default
+            case -1: continue;     // Write failed or timed out
+            case 0: return false;  // This is a master node
+            default:
+                if ((uint16_t)result == mesh_address) { // Successful address lookup if result == RF24Network address
+                    return true;
+                }
+                break;
         }
     }
-    return true;
+    return false;
 }
 
 /*****************************************************/

RF24Mesh_config.h

@@ -54,6 +54,16 @@
     #define MESH_MEM_ALLOC_SIZE 10
 #endif // MESH_MEM_ALLOC_SIZE
 
+/**
+ * @brief Number of attempts to verify a connection
+ *
+ * On child nodes, when calling `mesh.checkConnection();`, configure how many attempts will be made to contact the master node to verify connectivity
+ * Raising this number can result in a more stable mesh, since nodes can more easily verify that a connection is active
+ */
+#ifndef MESH_CONNECTION_CHECK_ATTEMPTS
+    #define MESH_CONNECTION_CHECK_ATTEMPTS 3
+#endif
+
 /**************************/
 /***       Debug        ***/
 //#define RF24MESH_DEBUG_MINIMAL /** Uncomment for the Master Node to print out address assignments as they are assigned */