Add Diag::SNIFFER so config verbosity of sniffer output

CommandStation-EX.ino

@@ -166,7 +166,8 @@ void loop()
     DCCPacket p = dccSniffer->fetchPacket();
     if (p.len() != 0) {
       if (DCCDecoder::parse(p)) {
-	p.print(Serial);
+	if (Diag::SNIFFER)
+	  p.print();
       }
     }
   }

DCCDecoder.cpp

@@ -42,7 +42,10 @@ bool DCCDecoder::parse(DCCPacket &p) {
   for (byte n = 0; n < p.len(); n++)
     checksum ^= d[n];
   if (checksum) {  // Result should be zero, if not it's an error!
+    if (Diag::SNIFFER) {
       DIAG(F("Checksum error"));
+      p.print();
+    }
     return false;
   }
 

DCCEXParser.cpp

@@ -1243,6 +1243,9 @@ bool DCCEXParser::parseD(Print *stream, int16_t params, int16_t p[])
     case "LCN"_hk: // <D LCN ON/OFF>
         Diag::LCN = onOff;
         return true;
+    case "SNIFFER"_hk: // <D SNIFFER ON/OFF>
+        Diag::SNIFFER = onOff;
+        return true;
 #endif
 #ifndef DISABLE_EEPROM
     case "EEPROM"_hk: // <D EEPROM NumEntries>

DCCPacket.h

@@ -20,6 +20,7 @@
 #ifndef DCCPacket_h
 #define DCCPacket_h
 #include <strings.h>
+#include "defines.h"
 
 class DCCPacket {
 public:
@@ -63,13 +64,15 @@ public:
       return true;
     return (bcmp(_data, right._data, _len) == 0);
   };
-  void print(HardwareSerial &s) {
-    s.print("<* DCCPACKET ");
+  void print() {
+    static const char hexchars[]="0123456789ABCDEF";
+    USB_SERIAL.print(F("<* DCCPACKET "));
     for (byte n = 0; n< _len; n++) {
-      s.print(_data[n], HEX);
-      s.print(" ");
+      USB_SERIAL.print(hexchars[_data[n]>>4]);
+      USB_SERIAL.print(hexchars[_data[n] & 0x0f]);
+      USB_SERIAL.print(' ');
     }
-    s.print("*>\n");
+    USB_SERIAL.print(F("*>\n"));
   };
   inline byte len() {return _len;};
   inline byte *data() {return _data;};

StringFormatter.cpp

@@ -27,6 +27,7 @@ bool Diag::WIFI=false;
 bool Diag::WITHROTTLE=false;
 bool Diag::ETHERNET=false;
 bool Diag::LCN=false;
+bool Diag::SNIFFER=false;
 
  
 void StringFormatter::diag( const FSH* input...) {

StringFormatter.h

@@ -30,7 +30,7 @@ class Diag {
   static bool WITHROTTLE;
   static bool ETHERNET;
   static bool LCN;
-  
+  static bool SNIFFER;
 };
 
 class StringFormatter