diff --git a/src/Adafruit_MCP23X18.cpp b/src/Adafruit_MCP23X18.cpp
new file mode 100644
index 0000000..d8accf4
--- /dev/null
+++ b/src/Adafruit_MCP23X18.cpp
@@ -0,0 +1,32 @@
+/*!
+ * @file Adafruit_MCP23X18.cpp
+ */
+
+#include "Adafruit_MCP23X18.h"
+
+/**************************************************************************/
+/*!
+  @brief default ctor.
+*/
+/**************************************************************************/
+Adafruit_MCP23X18::Adafruit_MCP23X18() { pinCount = 16; }
+
+/**************************************************************************/
+/*!
+  @brief Configures the specified pin to behave either as an input or an
+  output.
+  @param pin the Arduino pin number to set the mode of
+  @param mode INPUT, OUTPUT, or INPUT_PULLUP
+*/
+/**************************************************************************/
+void Adafruit_MCP23X18::pinMode(uint8_t pin, uint8_t mode) {
+  Adafruit_BusIO_Register IODIR(i2c_dev, spi_dev, MCP23XXX_SPIREG,
+                                getRegister(MCP23XXX_IODIR, MCP_PORT(pin)));
+  Adafruit_BusIO_Register GPPU(i2c_dev, spi_dev, MCP23XXX_SPIREG,
+                               getRegister(MCP23XXX_GPPU, MCP_PORT(pin)));
+  Adafruit_BusIO_RegisterBits dir_bit(&IODIR, 1, pin % 8);
+  Adafruit_BusIO_RegisterBits pullup_bit(&GPPU, 1, pin % 8);
+
+  dir_bit.write((mode == OUTPUT) ? 0 : 1);
+  pullup_bit.write((mode == INPUT_PULLUP || mode == OUTPUT_PULLUP) ? 1 : 0);
+}
\ No newline at end of file
diff --git a/src/Adafruit_MCP23X18.h b/src/Adafruit_MCP23X18.h
new file mode 100644
index 0000000..8cd97b1
--- /dev/null
+++ b/src/Adafruit_MCP23X18.h
@@ -0,0 +1,24 @@
+/*!
+ * @file Adafruit_MCP23X18.h
+ */
+
+#ifndef __ADAFRUIT_MCP23X18_H__
+#define __ADAFRUIT_MCP23X18_H__
+
+#include "Adafruit_MCP23X17.h"
+
+#define OUTPUT_PULLUP 4 //!< Additional define for Output with Pullup
+
+/**************************************************************************/
+/*!
+    @brief  Class for MCP23018 I2C and MCP23S18 SPI variants.
+*/
+/**************************************************************************/
+class Adafruit_MCP23X18 : public Adafruit_MCP23X17 {
+public:
+  Adafruit_MCP23X18();
+
+  void pinMode(uint8_t pin, uint8_t mode);
+};
+
+#endif