Makes the uarte endtx event available

This commit allows event_endtx to be used outside of the Uarte itself. As a consequence, PPI can be used to drive tasks given the end of transmission on the Uarte. This is particularly useful for situations like RS485 where a GPIO must be set to high when transmitting then cleared when done. A non-ppi approach can cause a delay in the clearing of this GPIO as other Embassy tasks might become scheduled.

embassy-nrf/src/uarte.rs

@@ -151,6 +151,12 @@ impl<'d, T: Instance> Uarte<'d, T> {
         (self.tx, self.rx)
     }
 
+    /// Return the endtx event for use with PPI
+    pub fn event_endtx(&self) -> Event {
+        let r = T::regs();
+        Event::from_reg(&r.events_endtx)
+    }
+
     fn on_interrupt(_: *mut ()) {
         let r = T::regs();
         let s = T::state();