Raising errors on non-inited periphs is SHOULD (requires overhead to implement).

Hardware-API.md

@@ -60,7 +60,7 @@ Conventions are:
 
 - Peripherals should provide default values for all the initialization arguments, this way when calling `.init()` with no params, or the constructor with only the peripheral id (or no id at all, then the default one is used), it will be initialized with the default configuration.
 
-- If a peripheral is in the non-initialized state, any operation on it except for `.init()` shall raise `OSError` with `EBUSY` code.
+- If a peripheral is in the non-initialized state, any operation on it except for `.init()` SHOULD raise `OSError` with `EBUSY` code.
 
 - When connecting a periph to some pins, one uses the `pins=` keyword in the constructor/init function.  This is a tuple/list of pins, where each pin can be an integer, string or `Pin` instance.