Any non-Copy wrapper type provided by the HAL should provide a free method that consumes the wrapper and returns back the raw peripheral (and possibly other objects) it was created from.

The method should shut down and reset the peripheral if necessary. Calling new with the raw peripheral returned by free should not fail due to an unexpected state of the peripheral.

If the HAL type requires other non-Copy objects to be constructed (for example I/O pins), any such object should be released and returned by free as well. free should return a tuple in that case.

For example:

# #![allow(unused_variables)]
#fn main() {
# pub struct TIMER0;
pub struct Timer(TIMER0);

impl Timer {
    pub fn new(periph: TIMER0) -> Self {
        Self(periph)
    }

    pub fn free(self) -> TIMER0 {
        self.0
    }
}
#}

HALs can be written on top of svd2rust-generated PACs, or on top of other crates that provide raw register access. HALs should always reexport the register access crate they are based on in their crate root.

A PAC should be reexported under the name pac, regardless of the actual name of the crate, as the name of the HAL should already make it clear what PAC is being accessed.

Types provided by the HAL should implement all applicable traits provided by the embedded-hal crate.

Multiple traits may be implemented for the same type.