diff --git a/advanced/common/usb/src/lib.rs b/advanced/common/usb/src/lib.rs
index 4b8ff2e..466e09a 100644
--- a/advanced/common/usb/src/lib.rs
+++ b/advanced/common/usb/src/lib.rs
@@ -6,6 +6,9 @@
 
 use core::num::NonZeroU8;
 
+/// Device address assigned by the host; will be in the range 1..=127
+pub type Address = NonZeroU8;
+
 /// Standard USB request
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum Request {
@@ -22,7 +25,7 @@ pub enum Request {
     // see section 9.4.6 of the USB specification
     SetAddress {
         /// New device address, in the range `1..=127`
-        address: Option<NonZeroU8>,
+        address: Option<Address>,
     },
 
     /// SET_CONFIGURATION
@@ -101,8 +104,6 @@ pub enum Descriptor {
     // there are even more descriptor types but we don't need to support them
 }
 
-/// Device address assigned by the host; will be in the range 1..=127
-pub type Address = NonZeroU8;
 /// The state of the USB device
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum DeviceState {
@@ -122,6 +123,7 @@ pub enum DeviceState {
 
 #[cfg(test)]
 mod tests {
+    #[cfg(TODO)]
     use core::num::NonZeroU8;
 
     use crate::{Descriptor, Request};
diff --git a/advanced/firmware/src/bin/usb-2-solution.rs b/advanced/firmware/src/bin/usb-2-solution.rs
index c49d430..9132adc 100644
--- a/advanced/firmware/src/bin/usb-2-solution.rs
+++ b/advanced/firmware/src/bin/usb-2-solution.rs
@@ -6,7 +6,7 @@ use dk::{
     usbd::{self, Event},
 };
 use panic_log as _; // panic handler
-use usb::{Descriptor, Request, DeviceState};
+use usb::{Address, Descriptor, DeviceState, Request};
 
 #[rtic::app(device = dk)]
 const APP: () = {
@@ -67,35 +67,35 @@ fn on_event(usbd: &USBD, state: &mut DeviceState, event: Event) {
                 wvalue
             );
 
-            // todo handle less indentedly?
-            if let Ok(request) = Request::parse(bmrequesttype, brequest, wvalue, windex, wlength) {
-                match request {
-                    Request::GetDescriptor { descriptor, length }
-                        if descriptor == Descriptor::Device =>
-                    {
-                        log::info!("GET_DESCRIPTOR Device [length={}]", length);
+            let request = Request::parse(bmrequesttype, brequest, wvalue, windex, wlength)
+                .expect("Error parsing request");
+            match request {
+                Request::GetDescriptor { descriptor, length }
+                    if descriptor == Descriptor::Device =>
+                {
+                    log::info!("GET_DESCRIPTOR Device [length={}]", length);
 
-                        log::info!("Goal reached; move to the next section");
-                        dk::exit()
-                    }
-                    Request::SetAddress { address } => {
-                        log::info!("SETUP: device state is {:?}", state);
-
-                        // todo hide this in a helper?
-                        // todo check for state configured -> err
-                        if let Some(address) = address {
-                            log::info!("SETUP: assigning address {}", address);
-                            *state = DeviceState::Address(address);
-                        } else {
-                            log::info!("SETUP: address was None; assigning Default");
-                            *state = DeviceState::Default;
-                        }
-                    }
-                    _ => unreachable!(), // we don't handle any other Requests
+                    log::info!("Goal reached; move to the next section");
+                    dk::exit()
                 }
-            } else {
-                unreachable!() // don't care about this for now
+                Request::SetAddress { address } => set_device_address(state, address),
+                _ => unreachable!(), // we don't handle any other Requests
             }
         }
     }
 }
+
+fn set_device_address(state: &mut DeviceState, address: Option<Address>) {
+    match state {
+        DeviceState::Default | DeviceState::Address(..) => {
+            if let Some(address) = address {
+                log::info!("SETUP: assigning device address {}", address);
+                *state = DeviceState::Address(address);
+            } else {
+                log::info!("SETUP: address was None; assigning Default");
+                *state = DeviceState::Default;
+            }
+        }
+        DeviceState::Configured { .. } => panic!(), // unspecified behavior
+    }
+}