pub fn is_busy(&self) -> bool {
        cfg_if::cfg_if! {
            if #[cfg(esp32)] {
                A::is_busy(&self.sha.borrow().sha)
            } else {
                self.sha.borrow().regs().busy().read().state().bit_is_set()
            }
        }
    }
Returns true if the hardware is processing the next message.
esp-hal/src/sha.rs