diff --git a/.gitignore b/.gitignore
index 6237359..9f44e98 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,3 +13,4 @@ myFilter.cpp
 my*.h
 !my*.example.h
 compile_commands.json
+*.yaml
diff --git a/CommandStation-EX.ino b/CommandStation-EX.ino
index 77e8f40..2e749a7 100644
--- a/CommandStation-EX.ino
+++ b/CommandStation-EX.ino
@@ -69,6 +69,11 @@
 void setup()
 {
   // The main sketch has responsibilities during setup()
+  pinMode(LED_BUILTIN, OUTPUT);
+  digitalWrite(LED_BUILTIN, LOW);
+
+  while(!Serial)
+    delay(100);
 
   // Responsibility 1: Start the usb connection for diagnostics
   // This is normally Serial but uses SerialUSB on a SAMD processor
diff --git a/DCCTimerRP2040.cpp b/DCCTimerRP2040.cpp
index 5245962..ae03836 100644
--- a/DCCTimerRP2040.cpp
+++ b/DCCTimerRP2040.cpp
@@ -42,11 +42,26 @@ INTERRUPT_CALLBACK interruptHandler=0;
 #define ALARM_NUM 0
 #define ALARM_IRQ TIMER_IRQ_0
 
+static uint32_t dcc_signal_time = 0;
+
+static void alarm_irq(void) {
+    // Clear the alarm irq
+    hw_clear_bits(&timer_hw->intr, 1u << ALARM_NUM);
+    // Reload timer
+    uint64_t target = timer_hw->timerawl + dcc_signal_time;
+    timer_hw->alarm[ALARM_NUM] = (uint32_t) target;
+
+    if (interruptHandler)
+      interruptHandler();
+}
+
 void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
+    interruptHandler = callback;
+    dcc_signal_time = DCC_SIGNAL_TIME;
     // Enable the interrupt for our alarm (the timer outputs 4 alarm irqs)
     hw_set_bits(&timer_hw->inte, 1u << ALARM_NUM);
     // Set irq handler for alarm irq
-    irq_set_exclusive_handler(ALARM_IRQ, callback);
+    irq_set_exclusive_handler(ALARM_IRQ, alarm_irq);
     // Enable the alarm irq
     irq_set_enabled(ALARM_IRQ, true);
     // Enable interrupt in block and at processor
@@ -54,7 +69,7 @@ void DCCTimer::begin(INTERRUPT_CALLBACK callback) {
     // Alarm is only 32 bits so if trying to delay more
     // than that need to be careful and keep track of the upper
     // bits
-    uint64_t target = timer_hw->timerawl + DCC_SIGNAL_TIME;
+    uint64_t target = timer_hw->timerawl + dcc_signal_time;
 
     // Write the lower 32 bits of the target time to the alarm which
     // will arm it
@@ -148,4 +163,3 @@ void ADCee::begin() {
 }
 
 #endif // RP2040
-
diff --git a/DCCWaveform.cpp b/DCCWaveform.cpp
index 4a99997..3479921 100644
--- a/DCCWaveform.cpp
+++ b/DCCWaveform.cpp
@@ -62,7 +62,7 @@ const bool signalTransform[]={
    /* WAVE_PENDING (should not happen) -> */ LOW};
 
 void DCCWaveform::begin() {
-  DCCTimer::begin(DCCWaveform::interruptHandler);     
+  DCCTimer::begin(DCCWaveform::interruptHandler);
 }
 
 void DCCWaveform::loop() {
@@ -71,7 +71,10 @@ void DCCWaveform::loop() {
 
 #pragma GCC push_options
 #pragma GCC optimize ("-O3")
+static uint32_t blinker = 0;
 void DCCWaveform::interruptHandler() {
+  if (!(blinker++ % 25000))
+    digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
   // call the timer edge sensitive actions for progtrack and maintrack
   // member functions would be cleaner but have more overhead
   byte sigMain=signalTransform[mainTrack.state];
diff --git a/MotorDriver.cpp b/MotorDriver.cpp
index a27b58c..0ff088f 100644
--- a/MotorDriver.cpp
+++ b/MotorDriver.cpp
@@ -91,7 +91,7 @@ MotorDriver::MotorDriver(int16_t power_pin, byte signal_pin, byte signal_pin2, i
     }
   }
   else dualSignal=false; 
-  
+
   if (brake_pin!=UNUSED_PIN){
     invertBrake=brake_pin < 0;
     if (invertBrake)
@@ -446,8 +446,6 @@ void  MotorDriver::getFastPin(const FSH* type,int pin, bool input, FASTPIN & res
     PortGroup *port = digitalPinToPort(pin);
 #elif defined(ARDUINO_ARCH_STM32)
     GPIO_TypeDef *port = digitalPinToPort(pin);
-#elif defined(ARDUINO_ARCH_RP2040)
-    volatile uint32_t port = 0;
 #else
     uint8_t port = digitalPinToPort(pin);
 #endif
diff --git a/MotorDriver.h b/MotorDriver.h
index a4884c4..84d2e03 100644
--- a/MotorDriver.h
+++ b/MotorDriver.h
@@ -61,6 +61,10 @@ enum TRACK_MODE : byte {TRACK_MODE_NONE = 1, TRACK_MODE_MAIN = 2, TRACK_MODE_PRO
 #define PORTC GPIOC->ODR
 #define HAVE_PORTC(X) X
 #endif
+#if defined(ARDUINO_ARCH_RP2040)
+#define HAVE_PORTA(X) X
+#define PORTA (sio_hw->gpio_out)
+#endif
 
 // if macros not defined as pass-through we define
 // them here as someting that is valid as a
diff --git a/MotorDrivers.h b/MotorDrivers.h
index 907c11b..2282238 100644
--- a/MotorDrivers.h
+++ b/MotorDrivers.h
@@ -59,7 +59,21 @@
 
 // Arduino STANDARD Motor Shield, used on different architectures:
 
-#if defined(ARDUINO_ARCH_SAMD) || defined(ARDUINO_ARCH_STM32)
+#if defined(ARDUINO_ARCH_RP2040)
+// Standard Motor Shield definition for RP2040
+// This setup is for the iLabs Challenger NB RP2040 WiFi board. Other boards likely need
+// a separate setup.
+#define STANDARD_MOTOR_SHIELD "STANDARD_MOTOR_SHIELD", \
+                              new MotorDriver(D17, D16, UNUSED_PIN, D15, A0, 0.488, 1500, UNUSED_PIN), \
+                              new MotorDriver(D14, D13, UNUSED_PIN, D12, A1, 0.488, 1500, UNUSED_PIN)
+#define RP2040_STANDARD_MOTOR_SHIELD STANDARD_MOTOR_SHIELD
+
+// EX 8874 based shield connected to a 3V3 system with 12-bit (4096) ADC
+#define EX8874_SHIELD "EX8874", \
+ new MotorDriver(D17, D16, UNUSED_PIN, D15, A0, 1.27, 5000, A4), \
+ new MotorDriver(D14, D13, UNUSED_PIN, D12, A1, 1.27, 5000, A5)
+
+#elif defined(ARDUINO_ARCH_SAMD) || defined(ARDUINO_ARCH_STM32)
 // Standard Motor Shield definition for 3v3 processors (other than the ESP32)
 // Setup for SAMD21 Sparkfun DEV board MUST use Arduino Motor Shield R3 (MUST be R3
 // for 3v3 compatibility!!) senseFactor for 3.3v systems is 1.95 as calculated when using