loopback update

examples/loopback.rs

@@ -50,6 +50,10 @@ app! {
             path: error_usart_overflow,
             priority: 1,
         },
+        EXTI4: {
+            path: rxne_not_set,
+            priority: 1,
+        },
     }
 }
 
@@ -104,7 +108,9 @@ fn usart2_handler(_t: &mut Threshold, r: USART2::Resources) {
                 r.USART2.dr.read(); // clear the error by reading the data register
             }
         }
-    }
+    } else {
+        // rxne not set
+        rtfm::set_pending(f4::stm32f40x::Interrupt::EXTI4);
 
         match r.SEND.dequeue() {
             Some(b) => {
@@ -117,6 +123,7 @@ fn usart2_handler(_t: &mut Threshold, r: USART2::Resources) {
             }
         }
     }
+}
 
 #[allow(non_snake_case)]
 fn command(
@@ -161,6 +168,10 @@ fn error_usart_overflow() {
     ipln!("error_usart_overflow");
 }
 
+fn rxne_not_set() {
+    ip!("-");
+}
+
 #[derive(Debug)]
 enum Command {
     Start,