remove blocking code and optimize for sleep

src/MKRWAN.h

@@ -496,12 +496,15 @@ class LoRaModem : public Stream
     pollInterval = secs * 1000;
   }
 
-  void poll() {
-    if (millis() - lastPollTime < pollInterval) return;
-    lastPollTime = millis();
+/**
+ * @brief Poll modem for status of a confirmed packet
+ * 
+ * @return int >0 indicates packet sent.  <0 indicates LORA_ERROR.
+ */
+  int poll() {
     // simply trigger a fake write
     uint8_t dummy = 0;
-    modemSend(&dummy, 1, true);
+    return modemSend(&dummy, 1, true);
   }
 
   bool factoryDefault() {
@@ -704,6 +707,55 @@ class LoRaModem : public Stream
     return fcd;
   }
 
+/**
+ * @brief Trigger the modem to send received data
+ *        For a Class C device, the module should not send a response if the host MCU (SAMD21) is sleeping.
+ *        Either the host needs to wake on RX or it needs to poll the module for a response.
+ *        This function is used in you want to poll the module for RX data.
+ *        Note, the module firmware should remove the call to at_Receive() in the LoraRxData() function defined in main.c
+ * 
+ * @return true if we received data from modem
+ * @return false if no response or LORA_ERROR
+ */
+  bool sendRXData() {
+    sendAT(GF("+RECV?"));
+    if (waitResponse(10) != 99) {
+      return false;
+    }
+    return true;
+  }
+
+/**
+ * @brief Get the Join Status from the modem
+ * 
+ * @return int -1: if timeout or LORA_ERROR,
+ *              0: if not joined
+ *              1: if joined
+ */
+  int getJoinStatus() {
+    sendAT(GF("+NJS?"));
+    if (waitResponse(2000L) != 1) {
+      return -1;
+    }
+    streamSkipUntil('=');
+    return stream.readStringUntil('\r').toInt();
+  }
+
+  /**
+   * @brief Get confirmation status of the last AT+SEND (0-1)
+   *        This can be used to poll the status of a confirmed uplink
+   *  Notes:  The McpsConfirmed() in lora.c (line 310) callback is called from LoRaMac.c (line 1378) when the mac state is idle. 
+   *          Presently, SX1276OnDio0Irq (sx1276.c line 1477) sends the "+ACK" string (line 1647) to the UART when a downlink is received.  This is incorrect.
+   *          It may be advantageous to notify the application using McpsConfirmed() when the uplink is confirmed.
+   * @return int 
+   */
+  int getCFS() {
+    int cfs = -1;
+    sendAT(GF("+CFS?"));
+    cfs = waitResponse("0", "1") - 1;
+    return cfs;
+  }
+
 
 private:
 
@@ -777,11 +829,6 @@ class LoRaModem : public Stream
     if (waitResponse() != 1) {
       return -1;
     }
-    if (confirmed) {
-        if (waitResponse(10000L, "+ACK") != 1) {
-            return -1;
-        }
-    }
     return len;
   }
 
@@ -797,15 +844,6 @@ class LoRaModem : public Stream
     return stream.readStringUntil('\r').toInt();
   }
 
-  size_t getJoinStatus() {
-    sendAT(GF("+NJS?"));
-    if (waitResponse(2000L) != 1) {
-      return 0;
-    }
-    streamSkipUntil('=');
-    return stream.readStringUntil('\r').toInt();
-  }
-
   /* Utilities */
   template<typename T>
   void streamWrite(T last) {
@@ -879,6 +917,8 @@ class LoRaModem : public Stream
                 i++;
             }
           }
+          index = 99;
+          goto finish;
         }
       }
     } while (millis() - startMillis < timeout);