diff --git a/CVReader.ino b/CVReader.ino
index 31c813c..9c378ec 100644
--- a/CVReader.ino
+++ b/CVReader.ino
@@ -85,7 +85,8 @@ void setup() {
   // The main sketch has responsibilities during setup()
   
   // Responsibility 1: Start the usb connection for diagnostics and possible JMRI input
-   Serial.begin(115200);
+  // DIAGSERAL is normally Serial but uses SerialUSB on a SAMD processor
+   DIAGSERIAL.begin(115200);
    
    // Responsibility 2: Start the DCC engine.   
    DCC::begin();
@@ -122,7 +123,7 @@ void loop() {
   DCC::loop(); 
 
   // Responsibility 2: handle any incoming commands on USB connection
-  serialParser.loop(Serial);
+  serialParser.loop(DIAGSERIAL);
 
   // Responsibility 3: Optionally handle any incoming WiFi traffic
 #ifdef WIFI
diff --git a/Hardware.cpp b/Hardware.cpp
index 5b3aa51..91e475d 100644
--- a/Hardware.cpp
+++ b/Hardware.cpp
@@ -17,7 +17,8 @@
  *  along with CommandStation.  If not, see <https://www.gnu.org/licenses/>.
  */
 #include <Arduino.h>
-#include <TimerOne.h>  // use IDE menu Tools..Manage Libraries to locate and  install TimerOne
+//#include <TimerOne.h>  // use IDE menu Tools..Manage Libraries to locate and  install TimerOne
+#include <ArduinoTimers.h>  // use IDE menu Tools..Manage Libraries to locate and  install TimerOne
 #include "avdweb_AnalogReadFast.h"
 #include "Hardware.h"
 #include "Config.h"
@@ -82,11 +83,10 @@ unsigned int Hardware::getCurrentMilliamps(bool isMainTrack, int raw) {
 }
 
 void Hardware::setCallback(int duration, void (*isr)()) {
-  Timer1.initialize(duration);
-  // We don't want the timer to set pins because these often clash with motor shields etc.
-  Timer1.disablePwm(TIMER1_A_PIN);
-  Timer1.disablePwm(TIMER1_B_PIN);
-  Timer1.attachInterrupt(isr);
+  TimerA.initialize();
+  TimerA.setPeriod(duration);
+  TimerA.attachInterrupt(isr);
+  TimerA.start();
 }
 
 // shortcut to cpu dependent high speed write 
diff --git a/StringFormatter.cpp b/StringFormatter.cpp
index 6fa1a9e..f7e7f25 100644
--- a/StringFormatter.cpp
+++ b/StringFormatter.cpp
@@ -18,12 +18,11 @@
  */
 #include "StringFormatter.h"
 #include <stdarg.h>
-
-
+      
 void StringFormatter::print( const __FlashStringHelper* input...) {
   va_list args;
   va_start(args, input);
-  send2(Serial,input,args);
+  send2(DIAGSERIAL,input,args);
 }
 
 void StringFormatter::send(Print & stream, const __FlashStringHelper* input...) {
diff --git a/StringFormatter.h b/StringFormatter.h
index 888eca9..7b25329 100644
--- a/StringFormatter.h
+++ b/StringFormatter.h
@@ -19,6 +19,15 @@
 #ifndef StringFormatter_h
 #define StringFormatter_h
 #include <Arduino.h>
+
+#if defined(ARDUINO_ARCH_SAMD)
+   // Some processors use a gcc compiler that renames va_list!!!
+  #include <cstdarg>
+  #define DIAGSERIAL SerialUSB
+#elif defined(ARDUINO_ARCH_AVR)
+  #define DIAGSERIAL Serial
+#endif
+
 class StringFormatter
 {
   public: