Merge pull request #6 from ferrous-systems/simplify_puzzle

Simplify puzzle

beginner/README.md

@@ -369,6 +369,8 @@ The Dongle will respond differently depending on the length of the incoming pack
 - On one-byte sized packets it will respond with the *direct* mapping from a *plaintext* letter -- the letter contained in the packet -- to the *ciphertext* letter.
 - On packets of any other length the Dongle will respond with the string `correct` if it received the decrypted string, otherwise it will respond with the `incorrect` string.
 
+The Dongle will always respond with packets that are valid UTF-8.
+
 Our suggestion is to use a dictionary / map. `std::collections::HashMap` is not available in `no_std` code (without linking to a global allocator) but you can use one of the maps in the [`heapless`] crate. To make this crate available in your application get the latest version from [crates.io] and add it to the `beginner/apps/Cargo.toml` file, for example:
 
 [`heapless`]: https://docs.rs/heapless

beginner/apps/src/bin/radio-puzzle.rs

@@ -23,12 +23,11 @@ fn main() -> ! {
     packet.copy_from_slice(msg.as_bytes());
     radio.send(&packet);
     log::info!("sent: {:?}", msg);
-    radio.recv(&mut packet).ok();
-    if let Ok(s) = str::from_utf8(&*packet) {
-        log::info!("received: {}", s);
-    } else {
-        log::info!("received: {:?}", &*packet);
+    // listen for a response packet and ensure it is not corrupted
+    if radio.recv(&mut packet).is_ok() {
+        // convert the packet contents to str or print error message on failure
+        let response = str::from_utf8(&*packet).expect("could not convert response to str");
+        log::info!("received: {}", response);
     }
-
     dk::exit()
 }