Use FIX2INT() for converting C/C++ values to Ruby

https://github.com/ruby/ruby/blob/trunk/doc/extension.rdoc

README.md

@@ -85,7 +85,9 @@ Bug reports and pull requests are welcome on GitHub at https://github.com/tubbo/
 
 ## License
 
-The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).
+This Ruby gem is available as open source under the terms of the [MIT
+License](http://opensource.org/licenses/MIT). The GrovePi C++ code is
+Copyright (C) 2017 Dexter Industries.
 
 ## Code of Conduct
 

ext/grovepi/grovepi.cpp

@@ -420,23 +420,23 @@ const char* GrovePi::I2CError::detail()
 // TODO: how to convert VALUE -> uint8_t || VALUE -> bool?
 namespace GrovePiRuby {
   static void digitalWrite(VALUE pin, VALUE data) {
-    GrovePi::digitalWrite(pin, data);
+    GrovePi::digitalWrite(FIX2INT(pin), data);
   }
 
   static VALUE digitalRead(VALUE pin) {
-    return rb_str_new2(GrovePi::digitalRead(pin));
+    return rb_str_new2(GrovePi::digitalRead(FIX2INT(pin)));
   }
 
   static void analogWrite(VALUE pin, VALUE data) {
-    return GrovePi::analogWrite(pin, data);
+    return GrovePi::analogWrite(FIX2INT(pin), data);
   }
 
   static VALUE analogRead(VALUE pin) {
-    return rb_str_new2(GrovePi::analogRead(pin));
+    return rb_str_new2(GrovePi::analogRead(FIX2INT(pin)));
   }
 
   static VALUE ultrasonicRead(VALUE pin) {
-    return rb_str_new2(GrovePi::ultrasonicRead(pin));
+    return rb_str_new2(GrovePi::ultrasonicRead(FIX2INT(pin)));
   }
 }