Added NOTACKNOWLEDGED

Author: PaulZC

examples/Example20_SendCustomCommand/Example20_SendCustomCommand.ino

@@ -2,7 +2,7 @@
   sendCustomCommand
   By: Paul Clark (PaulZC)
   Date: April 18th, 2020
-  
+
   License: MIT. See license file for more information but you can
   basically do whatever you want with this code.
 
@@ -61,7 +61,7 @@ void setup()
 
   // Let's configure the module's dynamic platform model as if we were using setDynamicModel
   // Possible values are:
-  // 0 (PORTABLE),   2 (STATIONARY), 3 (PEDESTRIAN), 4 (AUTOMOTIVE), 5 (SEA), 
+  // 0 (PORTABLE),   2 (STATIONARY), 3 (PEDESTRIAN), 4 (AUTOMOTIVE), 5 (SEA),
   // 6 (AIRBORNE1g), 7 (AIRBORNE2g), 8 (AIRBORNE4g), 9 (WRIST),     10 (BIKE)
 
   // Let's create our custom packet
@@ -85,6 +85,7 @@ void setup()
   // SFE_UBLOX_STATUS_DATA_RECEIVED if the data we requested was read / polled successfully
   // SFE_UBLOX_STATUS_DATA_SENT     if the data we sent was writted successfully (ACK'd)
   // Other values indicate errors. Please see the sfe_ublox_status_e enum for further details.
+  // If you see a failure you can of course simply try sending the same command again.
 
   // Referring to the u-blox M8 Receiver Description and Protocol Specification we see that
   // the dynamic model is configured using the UBX-CFG-NAV5 message. So let's load our
@@ -101,9 +102,18 @@ void setup()
   // Now let's read the current navigation model settings. The results will be loaded into customCfg.
   if (myGPS.sendCustomCommand(&customCfg, maxWait) != SFE_UBLOX_STATUS_DATA_RECEIVED) // We are expecting data and an ACK
   {
-    Serial.println(F("sendCustomCommand (poll) failed! Freezing."));
-    while (1)
-      ;      
+    Serial.println(F("sendCustomCommand (poll) failed! Trying again..."));
+    // We need to reset the packet before we try again as the values could have changed
+    customCfg.cls = UBX_CLASS_CFG;
+    customCfg.id = UBX_CFG_NAV5;
+    customCfg.len = 0;
+    customCfg.startingSpot = 0;
+    if (myGPS.sendCustomCommand(&customCfg, maxWait) != SFE_UBLOX_STATUS_DATA_RECEIVED) // We are expecting data and an ACK
+    {
+      Serial.println(F("sendCustomCommand (poll) failed again! Freezing."));
+      while (1)
+        ;
+    }
   }
 
   // Referring to the message definition for UBX-CFG-NAV5 we see that we need to change
@@ -133,7 +143,7 @@ void setup()
   {
     Serial.println(F("sendCustomCommand (set) failed! Freezing."));
     while (1)
-      ;      
+      ;
   }
   else
   {