Reduce the number of SD tries. Only print if SD was started.

Fix for #679

Author: nseidle

Firmware/RTK_Surveyor/Begin.ino

@@ -384,7 +384,7 @@ void beginSD()
 
             // Do a quick test to see if a card is present
             int tries = 0;
-            int maxTries = 5;
+            int maxTries = 2;
             while (tries < maxTries)
             {
                 if (sdPresent() == true)
@@ -397,7 +397,10 @@ void beginSD()
                 tries++;
             }
             if (tries == maxTries)
+            {
+                log_d("sdPresent failed");
                 break; // Give up loop
+            }
 
             // If an SD card is present, allow SdFat to take over
             log_d("SD card detected - using SPI and SdFat");

Firmware/RTK_Surveyor/SD.ino

@@ -37,6 +37,7 @@
 // within a reasonable amount of time, there is no SD card on the bus.
 // Returns false if not card is detected
 // Returns true if a card responds
+// This test takes approximately 13ms to complete
 bool sdPresent(void)
 {
     if (productVariant == REFERENCE_STATION)