diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 00000000..d35dce69
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,54 @@
+cmake_minimum_required(VERSION 4.0.0)
+
+project("Arduino Core API"
+        LANGUAGES CXX C ASM
+        VERSION 1.5.2.1
+        DESCRIPTION "Forked Arduino core API from v1.5.2"
+)
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_C_STANDARD 11)
+
+set(ARDUINO_CORE_API "arduino-core-api")
+
+add_library(${ARDUINO_CORE_API} INTERFACE)
+target_sources(${ARDUINO_CORE_API}
+        INTERFACE
+            api/CanMsg.cpp
+            api/CanMsgRingbuffer.cpp
+            api/Common.cpp
+            api/IPAddress.cpp
+            api/PluggableUSB.cpp
+            api/Print.cpp
+            api/Stream.cpp
+            api/String.cpp
+        INTERFACE FILE_SET arduino_core_headers TYPE HEADERS
+        BASE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}
+        FILES
+            api/ArduinoAPI.h
+            api/Binary.h
+            api/CanMsg.h
+            api/CanMsgRingbuffer.h
+            api/Client.h
+            api/Common.h
+            api/Compat.h
+            api/DMAPool.h
+            api/HardwareCAN.h
+            api/HardwareI2C.h
+            api/HardwareSerial.h
+            api/HardwareSPI.h
+            api/Interrupts.h
+            api/IPAddress.h
+            api/itoa.h
+            api/PluggableUSB.h
+            api/Print.h
+            api/Printable.h
+            api/RingBuffer.h
+            api/Server.h
+            api/Stream.h
+            api/String.h
+            api/Udp.h
+            api/USBAPI.h
+            api/WCharacter.h
+)
+
+add_library(ARDUINO::CORE_API ALIAS ${ARDUINO_CORE_API})
\ No newline at end of file
diff --git a/api/Common.h b/api/Common.h
index 9b28f40a..80629bca 100644
--- a/api/Common.h
+++ b/api/Common.h
@@ -36,11 +36,19 @@ typedef enum {
 } PinStatus;
 
 typedef enum {
-  INPUT            = 0x0,
-  OUTPUT           = 0x1,
-  INPUT_PULLUP     = 0x2,
-  INPUT_PULLDOWN   = 0x3,
-  OUTPUT_OPENDRAIN = 0x4,
+  // Normal Arduino API pin modes.
+  INPUT                  = 0x1,
+  INPUT_SCHMITT          = 0x2,
+  INPUT_PULLUP           = 0x3,
+  INPUT_SCHMITT_PULLUP   = 0x5,
+  INPUT_PULLDOWN         = 0x4,
+  INPUT_SCHMITT_PULLDOWN = 0x6,
+  // Drive strength modes added for Pico RP2040/RP2040
+  OUTPUT                 = 0x7,
+  OUTPUT_2mA             = 0x8,
+  OUTPUT_4mA             = 0x9,
+  OUTPUT_8mA             = 0xA,
+  OUTPUT_12mA            = 0xB
 } PinMode;
 
 typedef enum {
@@ -103,7 +111,7 @@ void initVariant(void);
 #ifndef HOST
 int atexit(void (*func)()) __attribute__((weak));
 #endif
-int main() __attribute__((weak));
+[[noreturn]] int main() __attribute__((weak));
 
 #ifdef EXTENDED_PIN_MODE
 // Platforms who want to declare more than 256 pins need to define EXTENDED_PIN_MODE globally
@@ -119,12 +127,12 @@ int analogRead(pin_size_t pinNumber);
 void analogReference(uint8_t mode);
 void analogWrite(pin_size_t pinNumber, int value);
 
-unsigned long millis(void);
-unsigned long micros(void);
+uint32_t millis(void);
+uint64_t micros(void);
 void delay(unsigned long);
 void delayMicroseconds(unsigned int us);
-unsigned long pulseIn(pin_size_t pin, uint8_t state, unsigned long timeout);
-unsigned long pulseInLong(pin_size_t pin, uint8_t state, unsigned long timeout);
+uint64_t pulseIn(pin_size_t pin, uint8_t state, unsigned long timeout);
+uint64_t pulseInLong(pin_size_t pin, uint8_t state, unsigned long timeout);
 
 void shiftOut(pin_size_t dataPin, pin_size_t clockPin, BitOrder bitOrder, uint8_t val);
 uint8_t shiftIn(pin_size_t dataPin, pin_size_t clockPin, BitOrder bitOrder);
@@ -175,8 +183,8 @@ uint16_t makeWord(byte h, byte l);
 
 #define word(...) makeWord(__VA_ARGS__)
 
-unsigned long pulseIn(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
-unsigned long pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
+uint64_t pulseIn(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
+uint64_t pulseInLong(uint8_t pin, uint8_t state, unsigned long timeout = 1000000L);
 
 void tone(uint8_t _pin, unsigned int frequency, unsigned long duration = 0);
 void noTone(uint8_t _pin);
diff --git a/api/Interrupts.h b/api/Interrupts.h
index c3e37ade..02e463c1 100644
--- a/api/Interrupts.h
+++ b/api/Interrupts.h
@@ -31,13 +31,15 @@ namespace arduino {
 template <typename T>
 using voidTemplateFuncPtrParam =  void (*)(T param);
 
-template<typename T> struct __container__ {
+template<typename T>
+struct __container__ {
   void* param;
   voidTemplateFuncPtrParam<T> function;
 };
 
 // C++ only overloaded version of attachInterrupt function
-template<typename T> void attachInterrupt(pin_size_t interruptNum, voidTemplateFuncPtrParam<T> userFunc, PinStatus mode, T& param) {
+template<typename T>
+void attachInterrupt(pin_size_t interruptNum, voidTemplateFuncPtrParam<T> userFunc, PinStatus mode, T& param) {
 
   struct __container__<T> *cont = new __container__<T>();
   cont->param = &param;
@@ -54,7 +56,8 @@ template<typename T> void attachInterrupt(pin_size_t interruptNum, voidTemplateF
   attachInterruptParam(interruptNum, f, mode, cont);
 }
 
-template<typename T> void attachInterrupt(pin_size_t interruptNum, voidTemplateFuncPtrParam<T*> userFunc, PinStatus mode, T* param) {
+template<typename T>
+void attachInterrupt(pin_size_t interruptNum, voidTemplateFuncPtrParam<T*> userFunc, PinStatus mode, T* param) {
   attachInterruptParam(interruptNum, (voidFuncPtrParam)userFunc, mode, (void*)param);
 }