diff --git a/Arduino/CanGrow/include/CanGrow_ESP32.h b/Arduino/CanGrow/include/CanGrow_ESP32.h
index d9fbdb1..2bbdc7c 100644
--- a/Arduino/CanGrow/include/CanGrow_ESP32.h
+++ b/Arduino/CanGrow/include/CanGrow_ESP32.h
@@ -30,3 +30,7 @@
 
 #define PinWIPE 2
 #define PinWIPE_default LOW
+#define Pin_I2C_SCL = 22;
+#define Pin_I2C_SDA = 21;
+
+// free usable pins
diff --git a/Arduino/CanGrow/include/CanGrow_ESP8266.h b/Arduino/CanGrow/include/CanGrow_ESP8266.h
index 260df47..1595039 100644
--- a/Arduino/CanGrow/include/CanGrow_ESP8266.h
+++ b/Arduino/CanGrow/include/CanGrow_ESP8266.h
@@ -30,3 +30,15 @@
 
 #define PinWIPE 2
 #define PinWIPE_default HIGH
+#define Pin_I2C_SCL = 5;
+#define Pin_I2C_SDA = 4;
+
+/*
+ * free usable pins
+ * - GPIO 0 / D3 boot fails if pulled LOW
+ * - GPIO 12 / D6
+ * - GPIO 13 / D7
+ * - GPIO 14 / D5
+ * - GPIO 15 / D8 Boot fails if pulled HIGH
+ * - GPIO 16 / D0
+ */