title: Is Bluetooth 4.2 compatible with 4.0?
body: <p>I was reading about the compatibility between BT 4.0 and 4.2. I found here and in another forum people saying it's full compatible. Also, according to what I read, the main differences would be basically security, speed and the IoT stuff. So if I run a simple BT connection (no IP) and don't require top speed transmission, can I rely on the fact that 4.0 and 4.2 will be compatible?</p>
  
  <p>My MCU library stack is 4.2 based but I want to make the product 4.0 compatible. Is there anything I should be aware of? Any other functionality/function I should not use?</p>