diff --git a/CommandStation-EX.ino b/CommandStation-EX.ino
index 219e245..1834228 100644
--- a/CommandStation-EX.ino
+++ b/CommandStation-EX.ino
@@ -85,8 +85,8 @@ void setup()
   EthernetInterface::setup();
 #endif // ETHERNET_ON
 
-// Initialise HAL layer before reading EEprom or setting up MotorDrivers 
-//  IODevice::begin();
+  // Initialise HAL layer before reading EEprom or setting up MotorDrivers 
+  IODevice::begin();
 
   // Responsibility 3: Start the DCC engine.
   // Note: this provides DCC with two motor drivers, main and prog, which handle the motor shield(s)
@@ -107,10 +107,10 @@ void setup()
     #undef SETUP
   #endif
 
-//  #if defined(LCN_SERIAL)
-//  LCN_SERIAL.begin(115200);
-//  LCN::init(LCN_SERIAL);
-//  #endif
+  #if defined(LCN_SERIAL)
+  LCN_SERIAL.begin(115200);
+  LCN::init(LCN_SERIAL);
+  #endif
   LCD(3, F("Ready"));
   CommandDistributor::broadcastPower();
 }
@@ -121,7 +121,7 @@ void loop()
 
   // Responsibility 1: Handle DCC background processes
   //                   (loco reminders and power checks)
-//  DCC::loop();
+  DCC::loop();
 
   // Responsibility 2: handle any incoming commands on USB connection
   SerialManager::loop();
@@ -134,18 +134,18 @@ void loop()
   EthernetInterface::loop();
 #endif
 
-//  RMFT::loop();  // ignored if no automation
+  RMFT::loop();  // ignored if no automation
 
   #if defined(LCN_SERIAL)
   LCN::loop();
   #endif
 
-//  LCDDisplay::loop();  // ignored if LCD not in use
+  LCDDisplay::loop();  // ignored if LCD not in use
 
   // Handle/update IO devices.
-  //IODevice::loop();
+  IODevice::loop();
 
-  //Sensor::checkAll(); // Update and print changes
+  Sensor::checkAll(); // Update and print changes
 
   // Report any decrease in memory (will automatically trigger on first call)
   static int ramLowWatermark = __INT_MAX__; // replaced on first loop
diff --git a/DCCTimerSAMD.cpp b/DCCTimerSAMD.cpp
index deff05b..159dd55 100644
--- a/DCCTimerSAMD.cpp
+++ b/DCCTimerSAMD.cpp
@@ -70,55 +70,59 @@ void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
                       GCLK_CLKCTRL_ID_TCC0_TCC1;      // Feed GCLK to TCC0/1
   while (GCLK->STATUS.bit.SYNCBUSY);
 
-  // PMA - assume we're using TCC0
-  REG_GCLK_GENDIV =   GCLK_GENDIV_DIV(1) |            // Divide 48MHz by 1
-                      GCLK_GENDIV_ID(4);              // Apply to GCLK4
-  while (GCLK->STATUS.bit.SYNCBUSY);                  // Wait for synchronization
-                
-  REG_GCLK_GENCTRL =  GCLK_GENCTRL_GENEN |            // Enable GCLK
-                      GCLK_GENCTRL_SRC_DFLL48M |      // Set the 48MHz clock source
-                      GCLK_GENCTRL_ID(4);             // Select GCLK4
-  while (GCLK->STATUS.bit.SYNCBUSY);                  // Wait for synchronization
-
-  REG_GCLK_CLKCTRL =  GCLK_CLKCTRL_CLKEN |            // Enable generic clock
-                      4 << GCLK_CLKCTRL_GEN_Pos |     // Apply to GCLK4
-                      GCLK_CLKCTRL_ID_TCC0_TCC1;      // Feed GCLK to TCC0/1
-  while (GCLK->STATUS.bit.SYNCBUSY);                  // Wait for synchronization
-
+  // PMA - assume we're using TCC0... as we're bit-bashing the DCC waveform output pins anyway
+  //       for "normal accuracy" DCC waveform generation. For high accuracy we're going to need
+  //       to a good deal more. The TCC waveform output pins are mux'd on the SAMD, and OP pins
+  //       for each TCC are only available on certain pins
   TCC0->WAVE.reg = TCC_WAVE_WAVEGEN_NPWM;     // Select NPWM as waveform
   while (TCC0->SYNCBUSY.bit.WAVE);            // Wait for sync
-  TCC0->INTENSET.reg = TCC_INTENSET_OVF;      // Interrupt on overflow
 
   // PMA - set the frequency
   TCC0->CTRLA.reg |= TCC_CTRLA_PRESCALER(TCC_CTRLA_PRESCALER_DIV1_Val);
-  unsigned long cycles = F_CPU / 10000000 * 58;   // 58uS to cycles
-  unsigned long pwmPeriod = cycles / 2;
-  TCC0->PER.reg = pwmPeriod;
+  TCC0->PER.reg = CLOCK_CYCLES * 2;
   while (TCC0->SYNCBUSY.bit.PER);
 
   // PMA - start it
   TCC0->CTRLA.bit.ENABLE = 1;
   while (TCC0->SYNCBUSY.bit.ENABLE);
 
+  // PMA - set interrupt condition, priority and enable
+  TCC0->INTENSET.reg = TCC_INTENSET_OVF;      // Only interrupt on overflow
+  NVIC_SetPriority((IRQn_Type)TCC0_IRQn, 0);  // Make this highest priority
   NVIC_EnableIRQ((IRQn_Type)TCC0_IRQn);       // Enable the interrupt
   interrupts();
 }
 
-// PMA - IRQ handler copied from rf24 branch
+// PMA - Timer IRQ handlers replace the dummy handlers (cortex_handlers)
+// copied from rf24 branch
 // TODO: test
 void TCC0_Handler() {
     if(TCC0->INTFLAG.bit.OVF) {
-        TCC0->INTFLAG.bit.OVF = 1;
+        TCC0->INTFLAG.bit.OVF = 1; // writing a 1 clears the flag
+        interruptHandler();
+    }
+}
+
+void TCC1_Handler() {
+    if(TCC1->INTFLAG.bit.OVF) {
+        TCC1->INTFLAG.bit.OVF = 1; // writing a 1 clears the flag
+        interruptHandler();
+    }
+}
+
+void TCC2_Handler() {
+    if(TCC2->INTFLAG.bit.OVF) {
+        TCC2->INTFLAG.bit.OVF = 1; // writing a 1 clears the flag
         interruptHandler();
     }
 }
 
 
 bool DCCTimer::isPWMPin(byte pin) {
-       //TODO: SAMD digitalPinHasPWM
-      (void) pin;
-       return false;  // TODO what are the relevant pins? 
-  }
+  //TODO: SAMD test this works!
+//  return digitalPinHasPWM(pin);
+  return false;
+}
 
 void DCCTimer::setPWM(byte pin, bool high) {
     // TODO: what are the relevant pins?
diff --git a/MotorDrivers.h b/MotorDrivers.h
index 74aab48..5237298 100644
--- a/MotorDrivers.h
+++ b/MotorDrivers.h
@@ -47,7 +47,8 @@
 //
 // Arduino standard Motor Shield
 #if defined(ARDUINO_ARCH_SAMD)
-// PMA - senseFactor for 3.3v systems is 1.95 as calculated when using 10-bit A/D samples,
+// PMA - Setup for SAMD21 Sparkfun DEV board
+// senseFactor for 3.3v systems is 1.95 as calculated when using 10-bit A/D samples,
 // and for 12-bit samples it's more like 0.488, but we probably need to tweak both these
 #define STANDARD_MOTOR_SHIELD F("STANDARD_MOTOR_SHIELD"),                                                 \
                               new MotorDriver(3, 12, UNUSED_PIN, 9, A0, 1.95, 2000, UNUSED_PIN), \