diff --git a/PCF8574.cpp b/PCF8574.cpp
index 9a235b0..1813f7e 100644
--- a/PCF8574.cpp
+++ b/PCF8574.cpp
@@ -22,7 +22,7 @@ PCF8574::PCF8574(uint8_t address, uint8_t interruptPin,  void (*interruptFunctio
 	_usingInterrupt = true;
 };
 
-#ifndef __AVR
+#if !defined(__AVR) && !defined(STM32F1)
 	/**
 	 * Constructor
 	 * @param address: i2c address
@@ -59,16 +59,16 @@ PCF8574::PCF8574(uint8_t address, uint8_t interruptPin,  void (*interruptFunctio
  * wake up i2c controller
  */
 void PCF8574::begin(){
-	#ifndef __AVR
+	#if !defined(__AVR) && !defined(STM32F1)
 		Wire.begin(_sda, _scl);
 	#else
-	//			Default pin for AVR some problem on software emulation
+	//			Default pin for AVR and Arduino STM32 some problem on software emulation
 	//			#define SCL_PIN _scl
 	// 			#define SDA_PIN _sda
 		Wire.begin();
 	#endif
 
-	// Che if there are pins to set low
+	// Check if there are pins to set low
 	if (writeMode>0 || readMode>0){
 		DEBUG_PRINTLN("Set write mode");
 		Wire.beginTransmission(_address);
diff --git a/PCF8574.h b/PCF8574.h
index 87036e4..449c7c4 100644
--- a/PCF8574.h
+++ b/PCF8574.h
@@ -91,8 +91,14 @@ public:
 
 private:
 	uint8_t _address;
-	uint8_t _sda = SDA;
-	uint8_t _scl = SCL;
+
+	#if !defined(__AVR) && !defined(STM32F1)
+		uint8_t _sda;
+		uint8_t _scl;
+	#else
+		uint8_t _sda = SDA;
+		uint8_t _scl = SCL;
+	#endif
 
 	bool _usingInterrupt = false;
 	uint8_t _interruptPin = 2;