diff --git a/macros/Cargo.toml b/macros/Cargo.toml
index 3aece07954..4237e21e8a 100644
--- a/macros/Cargo.toml
+++ b/macros/Cargo.toml
@@ -4,8 +4,13 @@ name = "cortex-m-rtfm-macros"
 version = "0.1.0"
 
 [dependencies]
+error-chain = "0.10.0"
 quote = "0.3.15"
 syn = "0.11.11"
 
+[dependencies.rtfm-syntax]
+git = "https://github.com/japaric/rtfm-syntax"
+optional = false
+
 [lib]
 proc-macro = true
diff --git a/macros/src/analyze.rs b/macros/src/analyze.rs
new file mode 100644
index 0000000000..0fc125daba
--- /dev/null
+++ b/macros/src/analyze.rs
@@ -0,0 +1,70 @@
+use std::cmp;
+use std::collections::HashMap;
+
+use syn::Ident;
+
+use check::App;
+
+pub type Ownerships = HashMap<Ident, Ownership>;
+
+pub enum Ownership {
+    /// Owned or co-owned by tasks that run at the same priority
+    Owned { priority: u8 },
+    /// Shared by tasks that run at different priorities.
+    ///
+    /// `ceiling` is the maximum value across all the task priorities
+    Shared { ceiling: u8 },
+}
+
+impl Ownership {
+    pub fn is_owned(&self) -> bool {
+        match *self {
+            Ownership::Owned { .. } => true,
+            _ => false,
+        }
+    }
+}
+
+pub fn app(app: &App) -> Ownerships {
+    let mut ownerships = HashMap::new();
+
+    for resource in &app.idle.resources {
+        ownerships.insert(resource.clone(), Ownership::Owned { priority: 0 });
+    }
+
+    for task in app.tasks.values() {
+        for resource in &task.resources {
+            if let Some(ownership) = ownerships.get_mut(resource) {
+                match *ownership {
+                    Ownership::Owned { priority } => {
+                        if priority == task.priority {
+                            *ownership = Ownership::Owned { priority };
+                        } else {
+                            *ownership = Ownership::Shared {
+                                ceiling: cmp::max(priority, task.priority),
+                            };
+                        }
+                    }
+                    Ownership::Shared { ceiling } => {
+                        if task.priority > ceiling {
+                            *ownership = Ownership::Shared {
+                                ceiling: task.priority,
+                            };
+                        }
+                    }
+                }
+
+                continue;
+            }
+
+            ownerships.insert(
+                resource.clone(),
+                Ownership::Owned {
+                    priority: task.priority,
+                },
+            );
+        }
+    }
+
+    ownerships
+}
diff --git a/macros/src/check.rs b/macros/src/check.rs
index 7c86326ac9..a459ab297e 100644
--- a/macros/src/check.rs
+++ b/macros/src/check.rs
@@ -1,12 +1,79 @@
-use syntax::Statics;
-use util::Ceilings;
+use std::collections::HashMap;
 
-pub fn resources(resources: &Statics, ceilings: &Ceilings) {
-    for resource in resources.keys() {
-        assert!(
-            ceilings.get(&resource).is_some(),
-            "resource {} is unused",
-            resource
+use quote::Tokens;
+use rtfm_syntax::{Idents, Idle, Init, Statics};
+use syn::Ident;
+
+use error::*;
+
+pub struct App {
+    pub device: Tokens,
+    pub idle: Idle,
+    pub init: Init,
+    pub resources: Statics,
+    pub tasks: Tasks,
+}
+
+pub type Tasks = HashMap<Ident, Task>;
+
+pub struct Task {
+    pub enabled: Option<bool>,
+    pub priority: u8,
+    pub resources: Idents,
+}
+
+pub fn app(app: ::rtfm_syntax::App) -> Result<App> {
+    let mut tasks = HashMap::new();
+
+    for (k, v) in app.tasks {
+        let name = k.clone();
+        tasks.insert(
+            k,
+            ::check::task(v)
+                .chain_err(|| format!("checking task `{}`", name))?,
         );
     }
+
+    let app = App {
+        device: app.device,
+        idle: app.idle,
+        init: app.init,
+        resources: app.resources,
+        tasks,
+    };
+
+    ::check::resources(&app)?;
+
+    Ok(app)
+}
+
+fn resources(app: &App) -> Result<()> {
+    for resource in app.resources.keys() {
+        if app.idle.resources.contains(resource) {
+            continue;
+        }
+
+        if app.tasks
+            .values()
+            .any(|task| task.resources.contains(resource))
+        {
+            continue;
+        }
+
+        bail!("resource `{}` is unused", resource);
+    }
+
+    Ok(())
+}
+
+fn task(task: ::rtfm_syntax::Task) -> Result<Task> {
+    if let Some(priority) = task.priority {
+        Ok(Task {
+            enabled: task.enabled,
+            priority,
+            resources: task.resources,
+        })
+    } else {
+        bail!("should contain a `priority` field")
+    }
 }
diff --git a/macros/src/error.rs b/macros/src/error.rs
new file mode 100644
index 0000000000..c044473728
--- /dev/null
+++ b/macros/src/error.rs
@@ -0,0 +1 @@
+error_chain!();
diff --git a/macros/src/lib.rs b/macros/src/lib.rs
index 10839eebce..467cbb9360 100644
--- a/macros/src/lib.rs
+++ b/macros/src/lib.rs
@@ -1,26 +1,44 @@
-#![deny(warnings)]
 #![feature(proc_macro)]
 #![recursion_limit = "128"]
 
+#[macro_use]
+extern crate error_chain;
 extern crate proc_macro;
 #[macro_use]
 extern crate quote;
+extern crate rtfm_syntax;
 extern crate syn;
 
-mod check;
-mod syntax;
-mod trans;
-mod util;
-
 use proc_macro::TokenStream;
+use rtfm_syntax::App;
+
+use error::*;
+
+mod analyze;
+mod check;
+mod error;
+mod trans;
 
 #[proc_macro]
 pub fn rtfm(ts: TokenStream) -> TokenStream {
+    match run(ts) {
+        Err(e) => panic!("{}", error_chain::ChainedError::display(&e)),
+        Ok(ts) => ts,
+    }
+}
+
+fn run(ts: TokenStream) -> Result<TokenStream> {
     let input = format!("{}", ts);
 
-    let app = syntax::parse::app(&input);
-    let ceilings = util::compute_ceilings(&app);
-    check::resources(&app.resources, &ceilings);
+    let app = check::app(App::parse(&input)
+        .chain_err(|| "parsing the `rtfm!` macro")?).chain_err(
+        || "checking the application specification",
+    )?;
 
-    format!("{}", trans::app(&app, &ceilings)).parse().unwrap()
+    let ownerships = analyze::app(&app);
+    let tokens = trans::app(&app, &ownerships);
+
+    Ok(format!("{}", tokens)
+        .parse()
+        .map_err(|_| "BUG: error parsing the generated code")?)
 }
diff --git a/macros/src/syntax/mod.rs b/macros/src/syntax/mod.rs
deleted file mode 100644
index 757e05ed95..0000000000
--- a/macros/src/syntax/mod.rs
+++ /dev/null
@@ -1,51 +0,0 @@
-use std::collections::{HashMap, HashSet};
-
-use syn::Ident;
-use quote::Tokens;
-
-pub mod parse;
-
-#[derive(Debug)]
-pub struct App {
-    pub device: Tokens,
-    pub idle: Idle,
-    pub init: Init,
-    pub resources: Statics,
-    pub tasks: Tasks,
-}
-
-#[derive(Debug)]
-pub struct Init {
-    pub path: Tokens,
-}
-
-#[derive(Debug)]
-pub struct Idle {
-    pub local: Statics,
-    pub path: Tokens,
-    pub resources: HashSet<Ident>,
-}
-
-#[derive(Debug)]
-pub struct Task {
-    pub kind: Kind,
-    pub priority: u8,
-    pub resources: HashSet<Ident>,
-}
-
-#[derive(Debug)]
-pub enum Kind {
-    Exception,
-    Interrupt { enabled: bool },
-}
-
-// $ident: $ty = $expr;
-#[derive(Debug)]
-pub struct Resource {
-    pub expr: Tokens,
-    pub ty: Tokens,
-}
-
-pub type Statics = HashMap<Ident, Resource>;
-
-pub type Tasks = HashMap<Ident, Task>;
diff --git a/macros/src/syntax/parse.rs b/macros/src/syntax/parse.rs
deleted file mode 100644
index 19b2511163..0000000000
--- a/macros/src/syntax/parse.rs
+++ /dev/null
@@ -1,522 +0,0 @@
-use std::collections::{HashMap, HashSet};
-
-use syn::{self, DelimToken, Ident, IntTy, Lit, Token, TokenTree};
-
-use syntax::{App, Idle, Init, Kind, Resource, Statics, Task, Tasks};
-
-pub fn app(input: &str) -> App {
-    let tts = syn::parse_token_trees(input).unwrap();
-
-    let mut device = None;
-    let mut init = None;
-    let mut idle = None;
-    let mut resources = None;
-    let mut tasks = None;
-
-    let mut tts = tts.into_iter();
-    while let Some(tt) = tts.next() {
-        let id = if let TokenTree::Token(Token::Ident(id)) = tt {
-            id
-        } else {
-            panic!("expected ident, found {:?}", tt);
-        };
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Colon)),
-            "expected colon, found {:?}",
-            tt
-        );
-
-        match id.as_ref() {
-            "device" => {
-                assert!(device.is_none(), "duplicated device field");
-
-                let mut pieces = vec![];
-
-                loop {
-                    if let Some(tt) = tts.next() {
-                        if tt == TokenTree::Token(Token::Comma) {
-                            break;
-                        } else {
-                            pieces.push(tt);
-                        }
-                    } else {
-                        panic!("expected path, found EOM");
-                    }
-                }
-
-                device = Some(quote!(#(#pieces)*));
-                continue;
-            }
-            "idle" => {
-                assert!(idle.is_none(), "duplicated idle field");
-
-                let tt = tts.next();
-                if let Some(TokenTree::Delimited(block)) = tt {
-                    assert_eq!(
-                        block.delim,
-                        DelimToken::Brace,
-                        "expected brace, found {:?}",
-                        block.delim
-                    );
-
-                    idle = Some(super::parse::idle(block.tts));
-                } else {
-                    panic!("expected block, found {:?}", tt);
-                }
-            }
-            "init" => {
-                assert!(init.is_none(), "duplicated init field");
-
-                let tt = tts.next();
-                if let Some(TokenTree::Delimited(block)) = tt {
-                    assert_eq!(
-                        block.delim,
-                        DelimToken::Brace,
-                        "expected brace, found {:?}",
-                        block.delim
-                    );
-
-                    init = Some(super::parse::init(block.tts));
-                } else {
-                    panic!("expected block, found {:?}", tt);
-                }
-            }
-            "resources" => {
-                assert!(resources.is_none(), "duplicated resources field");
-
-                let tt = tts.next();
-                if let Some(TokenTree::Delimited(block)) = tt {
-                    assert_eq!(
-                        block.delim,
-                        DelimToken::Brace,
-                        "expected brace, found {:?}",
-                        block.delim
-                    );
-
-                    resources = Some(super::parse::statics(block.tts));
-                }
-            }
-            "tasks" => {
-                assert!(tasks.is_none(), "duplicated tasks field");
-
-                let tt = tts.next();
-                if let Some(TokenTree::Delimited(block)) = tt {
-                    assert_eq!(
-                        block.delim,
-                        DelimToken::Brace,
-                        "expected brace, found {:?}",
-                        block.delim
-                    );
-
-                    tasks = Some(super::parse::tasks(block.tts));
-                }
-            }
-            id => panic!("unexpected field {}", id),
-        }
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Comma)),
-            "expected comma, found {:?}",
-            tt
-        );
-    }
-
-    App {
-        device: device.expect("device field is missing"),
-        idle: idle.expect("idle field is missing"),
-        init: init.expect("init field is missing"),
-        resources: resources.unwrap_or(HashMap::new()),
-        tasks: tasks.unwrap_or(HashMap::new()),
-    }
-}
-
-pub fn idle(tts: Vec<TokenTree>) -> Idle {
-    let mut tts = tts.into_iter();
-
-    let mut local = None;
-    let mut path = None;
-    let mut resources = None;
-    while let Some(tt) = tts.next() {
-        let id = if let TokenTree::Token(Token::Ident(id)) = tt {
-            id
-        } else {
-            panic!("expected ident, found {:?}", tt);
-        };
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Colon)),
-            "expected colon, found {:?}",
-            tt
-        );
-
-        match id.as_ref() {
-            "local" => {
-                assert!(local.is_none(), "duplicated local field");
-
-                let tt = tts.next();
-                if let Some(TokenTree::Delimited(block)) = tt {
-                    assert_eq!(
-                        block.delim,
-                        DelimToken::Brace,
-                        "expected brace, found {:?}",
-                        block.delim
-                    );
-
-                    local = Some(super::parse::statics(block.tts));
-                } else {
-                    panic!("expected block, found {:?}", tt);
-                }
-            }
-            "path" => {
-                assert!(path.is_none(), "duplicated path field");
-
-                let mut pieces = vec![];
-                loop {
-                    let tt = tts.next()
-                        .expect("expected comma, found end of macro");
-
-                    if tt == TokenTree::Token(Token::Comma) {
-                        path = Some(quote!(#(#pieces)*));
-                        break;
-                    } else {
-                        pieces.push(tt);
-                    }
-                }
-
-                continue;
-            }
-            "resources" => {
-                assert!(resources.is_none(), "duplicated resources field");
-
-                let tt = tts.next();
-                if let Some(TokenTree::Delimited(array)) = tt {
-                    assert_eq!(
-                        array.delim,
-                        DelimToken::Bracket,
-                        "expected bracket, found {:?}",
-                        array.delim
-                    );
-
-                    resources = Some(super::parse::idents(array.tts));
-
-                } else {
-                    panic!("expected array, found {:?}", tt);
-                }
-            }
-            id => panic!("unexpected field {}", id),
-        }
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Comma)),
-            "expected comma, found {:?}",
-            tt
-        );
-    }
-
-    Idle {
-        local: local.unwrap_or(HashMap::new()),
-        path: path.expect("path field is missing"),
-        resources: resources.unwrap_or(HashSet::new()),
-    }
-}
-
-pub fn init(tts: Vec<TokenTree>) -> Init {
-    let mut tts = tts.into_iter();
-
-    let mut path = None;
-    while let Some(tt) = tts.next() {
-        let id = if let TokenTree::Token(Token::Ident(id)) = tt {
-            id
-        } else {
-            panic!("expected ident, found {:?}", tt);
-        };
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Colon)),
-            "expected colon, found {:?}",
-            tt
-        );
-
-        match id.as_ref() {
-            "path" => {
-                let mut pieces = vec![];
-                loop {
-                    let tt = tts.next()
-                        .expect("expected comma, found end of macro");
-
-                    if tt == TokenTree::Token(Token::Comma) {
-                        path = Some(quote!(#(#pieces)*));
-                        break;
-                    } else {
-                        pieces.push(tt);
-                    }
-                }
-            }
-            id => panic!("unexpected field {}", id),
-        }
-    }
-
-    Init { path: path.expect("path field is missing") }
-}
-
-fn idents(tts: Vec<TokenTree>) -> HashSet<Ident> {
-    let mut idents = HashSet::new();
-
-    let mut tts = tts.into_iter().peekable();
-    while let Some(tt) = tts.next() {
-        if let TokenTree::Token(Token::Ident(id)) = tt {
-            assert!(!idents.contains(&id), "ident {} already listed", id);
-            idents.insert(id);
-
-            if let Some(tt) = tts.next() {
-                assert_eq!(tt, TokenTree::Token(Token::Comma));
-
-                if tts.peek().is_none() {
-                    break;
-                }
-            } else {
-                break;
-            }
-        } else {
-            panic!("expected ident, found {:?}", tt);
-        };
-    }
-
-    idents
-}
-
-pub fn statics(tts: Vec<TokenTree>) -> Statics {
-    let mut resources = HashMap::new();
-
-    let mut tts = tts.into_iter();
-    while let Some(tt) = tts.next() {
-        let name = if let TokenTree::Token(Token::Ident(ident)) = tt {
-            ident
-        } else {
-            panic!("expected ident, found {:?}", tt);
-        };
-
-        assert!(
-            !resources.contains_key(&name),
-            "resource {} already listed",
-            name
-        );
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Colon)),
-            "expected comma, found {:?}",
-            tt
-        );
-
-        let mut pieces = vec![];
-        loop {
-            if let Some(tt) = tts.next() {
-                if tt == TokenTree::Token(Token::Eq) {
-                    break;
-                } else {
-                    pieces.push(tt);
-                }
-            } else {
-                panic!("expected type, found EOM");
-            }
-        }
-
-        let ty = quote!(#(#pieces)*);
-
-        let mut pieces = vec![];
-        loop {
-            if let Some(tt) = tts.next() {
-                if tt == TokenTree::Token(Token::Semi) {
-                    break;
-                } else {
-                    pieces.push(tt);
-                }
-            } else {
-                panic!("expected expression, found EOM");
-            }
-        }
-
-        let expr = quote!(#(#pieces)*);
-
-        let resource = Resource { expr, ty };
-        resources.insert(name, resource);
-    }
-
-    resources
-}
-
-pub fn tasks(tts: Vec<TokenTree>) -> Tasks {
-    let mut tasks = HashMap::new();
-
-    let mut tts = tts.into_iter();
-    while let Some(tt) = tts.next() {
-        let name = if let TokenTree::Token(Token::Ident(ident)) = tt {
-            ident
-        } else {
-            panic!("expected ident, found {:?}", tt);
-        };
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Colon)),
-            "expected colon, found {:?}",
-            tt
-        );
-
-        let tt = tts.next();
-        if let Some(TokenTree::Delimited(block)) = tt {
-            assert_eq!(
-                block.delim,
-                DelimToken::Brace,
-                "expected brace, found {:?}",
-                block.delim
-            );
-
-            assert!(!tasks.contains_key(&name), "task {} already listed", name);
-            tasks.insert(name, super::parse::task(block.tts));
-        } else {
-            panic!("expected block, found {:?}", tt);
-        }
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Comma)),
-            "expected comma, found {:?}",
-            tt
-        );
-    }
-
-    tasks
-}
-
-/// Parses the body of a task
-///
-/// ```
-///     enabled: true,
-///     priority: 1,
-///     resources: [R1, TIM2],
-/// ```
-///
-/// the `enabled` field is optional and distinguishes interrupts from
-/// exceptions. Interrupts have an `enabled` field, whereas exceptions don't.
-fn task(tts: Vec<TokenTree>) -> Task {
-    let mut enabled = None;
-    let mut priority = None;
-    let mut resources = None;
-
-    let mut tts = tts.into_iter();
-    while let Some(tt) = tts.next() {
-        let ident = if let TokenTree::Token(Token::Ident(ident)) = tt {
-            ident
-        } else {
-            panic!("expected ident, found {:?}", tt);
-        };
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Colon)),
-            "expected colon, found {:?}",
-            tt
-        );
-
-        match ident.as_ref() {
-            "enabled" => {
-                assert!(enabled.is_none(), "duplicated enabled field");
-
-                let tt = tts.next();
-
-                if let Some(TokenTree::Token(Token::Literal(lit))) = tt {
-                    if let Lit::Bool(b) = lit {
-                        enabled = Some(b);
-                    } else {
-                        panic!("`enabled` value must be a boolean");
-                    }
-                } else {
-                    panic!("expected literal, found {:?}", tt);
-                }
-            }
-            "priority" => {
-                assert!(priority.is_none(), "duplicated priority field");
-
-                let tt = tts.next();
-
-                if let Some(TokenTree::Token(Token::Literal(lit))) = tt {
-                    if let Lit::Int(val, ty) = lit {
-                        assert_eq!(
-                            ty,
-                            IntTy::Unsuffixed,
-                            "`priority` value must be an unsuffixed value"
-                        );
-
-                        assert!(
-                            val < 256,
-                            "`priority` value must be less than 256"
-                        );
-
-                        priority = Some(val as u8);
-                    } else {
-                        panic!("enabled value must be a boolean");
-                    }
-                } else {
-                    panic!("expected literal, found {:?}", tt);
-                }
-            }
-            "resources" => {
-                assert!(resources.is_none(), "duplicated resources field");
-
-                let tt = tts.next();
-                if let Some(TokenTree::Delimited(block)) = tt {
-                    assert_eq!(
-                        block.delim,
-                        DelimToken::Bracket,
-                        "expected bracket, found {:?}",
-                        block.delim
-                    );
-
-                    resources = Some(super::parse::idents(block.tts));
-                } else {
-                    panic!("expected block, found {:?}", tt);
-                }
-            }
-            id => panic!("unexpected field {}", id),
-        }
-
-        let tt = tts.next();
-        assert_eq!(
-            tt,
-            Some(TokenTree::Token(Token::Comma)),
-            "expected comma, found {:?}",
-            tt
-        );
-    }
-
-    let resources = resources.unwrap_or(HashSet::new());
-    let priority = priority.expect("priority field is missing");
-    let kind = if let Some(enabled) = enabled {
-        Kind::Interrupt { enabled }
-    } else {
-        Kind::Exception
-    };
-
-    Task {
-        kind,
-        priority,
-        resources,
-    }
-}
diff --git a/macros/src/trans.rs b/macros/src/trans.rs
index 13dc51d186..7f5b2787f9 100644
--- a/macros/src/trans.rs
+++ b/macros/src/trans.rs
@@ -1,21 +1,21 @@
-use quote::Tokens;
-use syn::Ident;
+use quote::{Ident, Tokens};
 
-use syntax::{App, Kind};
-use util::{Ceiling, Ceilings};
+use analyze::{Ownership, Ownerships};
+use check::App;
 
 fn krate() -> Ident {
-    Ident::new("rtfm")
+    Ident::from("rtfm")
 }
 
-pub fn app(app: &App, ceilings: &Ceilings) -> Tokens {
-    let mut main = vec![];
+pub fn app(app: &App, ownerships: &Ownerships) -> Tokens {
     let mut root = vec![];
+    let mut main = vec![];
 
-    super::trans::init(app, &mut main, &mut root);
-    super::trans::idle(app, ceilings, &mut main, &mut root);
-    super::trans::resources(app, ceilings, &mut root);
-    super::trans::tasks(app, ceilings, &mut root);
+    // ::trans::check(app, &mut main);
+    ::trans::init(app, &mut main, &mut root);
+    ::trans::idle(app, ownerships, &mut main, &mut root);
+    ::trans::resources(app, ownerships, &mut root);
+    ::trans::tasks(app, ownerships, &mut root);
 
     root.push(quote! {
         fn main() {
@@ -26,127 +26,15 @@ pub fn app(app: &App, ceilings: &Ceilings) -> Tokens {
     quote!(#(#root)*)
 }
 
-fn init(app: &App, main: &mut Vec<Tokens>, root: &mut Vec<Tokens>) {
-    let device = &app.device;
-    let krate = krate();
-
-    let mut tys = vec![quote!(init::Peripherals)];
-    let mut exprs = vec![quote!(init::Peripherals::all())];
-    let mut mod_items = vec![];
-
-    if !app.resources.is_empty() {
-        let mut fields = vec![];
-        let mut lifetime = None;
-        let mut rexprs = vec![];
-
-        for (name, resource) in &app.resources {
-            lifetime = Some(quote!('a));
-
-            let ty = &resource.ty;
-
-            fields.push(quote! {
-                pub #name: &'a mut #krate::Static<#ty>,
-            });
-
-            rexprs.push(quote! {
-                #name: ::#krate::Static::ref_mut(&mut *super::#name.get()),
-            });
-        }
-
-        root.push(quote! {
-            #[allow(non_camel_case_types)]
-            #[allow(non_snake_case)]
-            pub struct _initResources<#lifetime> {
-                #(#fields)*
-            }
-        });
-
-        mod_items.push(quote! {
-            pub use ::_initResources as Resources;
-
-            impl<#lifetime> Resources<#lifetime> {
-                pub unsafe fn new() -> Self {
-                    Resources {
-                        #(#rexprs)*
-                    }
-                }
-            }
-        });
-
-        tys.push(quote!(init::Resources));
-        exprs.push(quote!(init::Resources::new()));
-    }
-
-    root.push(quote! {
-        mod init {
-            pub use ::#device::Peripherals;
-
-            #(#mod_items)*
-        }
-    });
-
-    let mut exceptions = vec![];
-    let mut interrupts = vec![];
-    for (name, task) in &app.tasks {
-        match task.kind {
-            Kind::Exception => {
-                if exceptions.is_empty() {
-                    exceptions.push(quote! {
-                        let scb = #device::SCB.borrow(_cs);
-                    });
-                }
-
-                let priority = task.priority;
-                exceptions.push(quote! {
-                    let prio_bits = #device::NVIC_PRIO_BITS;
-                    let hw = ((1 << prio_bits) - #priority) << (8 - prio_bits);
-                    scb.shpr[#krate::Exception::#name.nr() - 4].write(hw);
-                });
-            }
-            Kind::Interrupt { enabled } => {
-                if interrupts.is_empty() {
-                    interrupts.push(quote! {
-                        let nvic = #device::NVIC.borrow(_cs);
-                    });
-                }
-
-                let priority = task.priority;
-                interrupts.push(quote! {
-                    let prio_bits = #device::NVIC_PRIO_BITS;
-                    let hw = ((1 << prio_bits) - #priority) << (8 - prio_bits);
-                    nvic.set_priority(#device::Interrupt::#name, hw);
-                });
-
-                if enabled {
-                    interrupts.push(quote! {
-                        nvic.enable(#device::Interrupt::#name);
-                    });
-                } else {
-                    interrupts.push(quote! {
-                        nvic.disable(#device::Interrupt::#name);
-                    });
-                }
-            }
-        }
-    }
-
-    let init = &app.init.path;
-    main.push(quote! {
-        // type check
-        let init: fn(#(#tys,)*) = #init;
-
-        #krate::atomic(|_cs| unsafe {
-            init(#(#exprs,)*);
-
-            #(#exceptions)*
-            #(#interrupts)*
-        });
-    });
-}
+// Check that the exceptions / interrupts are valid
+// Sadly we can't do this test at expansion time. Instead we'll generate some
+// code that won't compile if the interrupt name is invalid.
+// fn check(app: &App, main: &mut Vec<Tokens>) {
+// }
 
 fn idle(
     app: &App,
-    ceilings: &Ceilings,
+    ownerships: &Ownerships,
     main: &mut Vec<Tokens>,
     root: &mut Vec<Tokens>,
 ) {
@@ -160,17 +48,17 @@ fn idle(
         !app.idle
             .resources
             .iter()
-            .all(|resource| ceilings[resource].is_owned())
+            .all(|resource| ownerships[resource].is_owned())
     {
         tys.push(quote!(#krate::Threshold));
         exprs.push(quote!(unsafe { #krate::Threshold::new(0) }));
     }
 
-    if !app.idle.local.is_empty() {
+    if !app.idle.locals.is_empty() {
         let mut lexprs = vec![];
         let mut lfields = vec![];
 
-        for (name, resource) in &app.idle.local {
+        for (name, resource) in &app.idle.locals {
             let expr = &resource.expr;
             let ty = &resource.ty;
 
@@ -184,16 +72,16 @@ fn idle(
         }
 
         mod_items.push(quote! {
-            pub struct Local {
+            pub struct Locals {
                 #(#lfields)*
             }
         });
 
-        tys.push(quote!(&'static mut idle::Local));
-        exprs.push(quote!(unsafe { &mut LOCAL }));
+        tys.push(quote!(&'static mut idle::Locals));
+        exprs.push(quote!(unsafe { &mut LOCALS }));
 
         main.push(quote! {
-            static mut LOCAL: idle::Local = idle::Local {
+            static mut LOCALS: idle::Locals = idle::Locals {
                 #(#lexprs)*
             };
         });
@@ -205,10 +93,10 @@ fn idle(
 
         let mut needs_reexport = false;
         for name in &app.idle.resources {
-            if ceilings[name].is_owned() {
+            if ownerships[name].is_owned() {
                 if app.resources.get(name).is_some() {
                     needs_reexport = true;
-                    break
+                    break;
                 }
             }
         }
@@ -221,7 +109,7 @@ fn idle(
         let mut rexprs = vec![];
         let mut rfields = vec![];
         for name in &app.idle.resources {
-            if ceilings[name].is_owned() {
+            if ownerships[name].is_owned() {
                 lifetime = Some(quote!('a));
                 if let Some(resource) = app.resources.get(name) {
                     let ty = &resource.ty;
@@ -305,7 +193,282 @@ fn idle(
     });
 }
 
-fn tasks(app: &App, ceilings: &Ceilings, root: &mut Vec<Tokens>) {
+fn init(app: &App, main: &mut Vec<Tokens>, root: &mut Vec<Tokens>) {
+    let device = &app.device;
+    let krate = krate();
+
+    let mut tys = vec![quote!(#device::Peripherals)];
+    let mut exprs = vec![quote!(#device::Peripherals::all())];
+    let mut mod_items = vec![];
+
+    if !app.resources.is_empty() {
+        let mut fields = vec![];
+        let mut lifetime = None;
+        let mut rexprs = vec![];
+
+        for (name, resource) in &app.resources {
+            lifetime = Some(quote!('a));
+
+            let ty = &resource.ty;
+
+            fields.push(quote! {
+                pub #name: &'a mut #krate::Static<#ty>,
+            });
+
+            rexprs.push(quote! {
+                #name: ::#krate::Static::ref_mut(&mut *super::#name.get()),
+            });
+        }
+
+        root.push(quote! {
+            #[allow(non_camel_case_types)]
+            #[allow(non_snake_case)]
+            pub struct _initResources<#lifetime> {
+                #(#fields)*
+            }
+        });
+
+        mod_items.push(quote! {
+            pub use ::_initResources as Resources;
+
+            impl<#lifetime> Resources<#lifetime> {
+                pub unsafe fn new() -> Self {
+                    Resources {
+                        #(#rexprs)*
+                    }
+                }
+            }
+        });
+
+        tys.push(quote!(init::Resources));
+        exprs.push(quote!(init::Resources::new()));
+    }
+
+    root.push(quote! {
+        mod init {
+            pub use ::#device::Peripherals;
+
+            #(#mod_items)*
+        }
+    });
+
+    let mut exceptions = vec![];
+    let mut interrupts = vec![];
+    for (name, task) in &app.tasks {
+        if let Some(enabled) = task.enabled {
+            // Interrupt. These can be enabled / disabled through the NVIC
+            if interrupts.is_empty() {
+                interrupts.push(quote! {
+                    let nvic = #device::NVIC.borrow(_cs);
+                });
+            }
+
+            let priority = task.priority;
+            interrupts.push(quote! {
+                let prio_bits = #device::NVIC_PRIO_BITS;
+                let hw = ((1 << prio_bits) - #priority) << (8 - prio_bits);
+                nvic.set_priority(#device::Interrupt::#name, hw);
+            });
+
+            if enabled {
+                interrupts.push(quote! {
+                    nvic.enable(#device::Interrupt::#name);
+                });
+            } else {
+                interrupts.push(quote! {
+                    nvic.disable(#device::Interrupt::#name);
+                });
+            }
+        } else {
+            // Exception
+            if exceptions.is_empty() {
+                exceptions.push(quote! {
+                    let scb = #device::SCB.borrow(_cs);
+                });
+            }
+
+            let priority = task.priority;
+            exceptions.push(quote! {
+                let prio_bits = #device::NVIC_PRIO_BITS;
+                let hw = ((1 << prio_bits) - #priority) << (8 - prio_bits);
+                scb.shpr[#krate::Exception::#name.nr() - 4].write(hw);
+            });
+        }
+    }
+
+    let init = &app.init.path;
+    main.push(quote! {
+        // type check
+        let init: fn(#(#tys,)*) = #init;
+
+        #krate::atomic(|_cs| unsafe {
+            init(#(#exprs,)*);
+
+            #(#exceptions)*
+            #(#interrupts)*
+        });
+    });
+}
+
+fn resources(app: &App, ownerships: &Ownerships, root: &mut Vec<Tokens>) {
+    let krate = krate();
+    let device = &app.device;
+
+    let mut items = vec![];
+    let mut impls = vec![];
+    for (name, ownership) in ownerships {
+        let mut impl_items = vec![];
+
+        match *ownership {
+            Ownership::Owned { .. } => {
+                if let Some(resource) = app.resources.get(name) {
+                    // For owned resources we don't need claim() or borrow(),
+                    // just get()
+                    let expr = &resource.expr;
+                    let ty = &resource.ty;
+
+                    root.push(quote! {
+                        static #name: #krate::Resource<#ty> =
+                            #krate::Resource::new(#expr);
+                    });
+                } else {
+                    // Peripheral
+                    continue;
+                }
+            }
+            Ownership::Shared { ceiling } => {
+                if let Some(resource) = app.resources.get(name) {
+                    let expr = &resource.expr;
+                    let ty = &resource.ty;
+
+                    root.push(quote! {
+                        static #name: #krate::Resource<#ty> =
+                            #krate::Resource::new(#expr);
+                    });
+
+                    impl_items.push(quote! {
+                        pub fn borrow<'cs>(
+                            &'cs self,
+                            cs: &'cs #krate::CriticalSection,
+                        ) -> &'cs #krate::Static<#ty> {
+                            unsafe { #name.borrow(cs) }
+                        }
+
+                        pub fn borrow_mut<'cs>(
+                            &'cs mut self,
+                            cs: &'cs #krate::CriticalSection,
+                        ) -> &'cs mut #krate::Static<#ty> {
+                            unsafe { #name.borrow_mut(cs) }
+                        }
+
+                        pub fn claim<R, F>(
+                            &self,
+                            t: &mut #krate::Threshold,
+                            f: F,
+                        ) -> R
+                        where
+                            F: FnOnce(
+                                &#krate::Static<#ty>,
+                                &mut #krate::Threshold) -> R
+                        {
+                            unsafe {
+                                #name.claim(
+                                    #ceiling,
+                                    #device::NVIC_PRIO_BITS,
+                                    t,
+                                    f,
+                                )
+                            }
+                        }
+
+                        pub fn claim_mut<R, F>(
+                            &mut self,
+                            t: &mut #krate::Threshold,
+                            f: F,
+                        ) -> R
+                        where
+                            F: FnOnce(
+                                &mut #krate::Static<#ty>,
+                                &mut #krate::Threshold) -> R
+                        {
+                            unsafe {
+                                #name.claim_mut(
+                                    #ceiling,
+                                    #device::NVIC_PRIO_BITS,
+                                    t,
+                                    f,
+                                )
+                            }
+                        }
+                    });
+                } else {
+                    root.push(quote! {
+                        static #name: #krate::Peripheral<#device::#name> =
+                            #krate::Peripheral::new(#device::#name);
+                    });
+
+                    impl_items.push(quote! {
+                        pub fn borrow<'cs>(
+                            &'cs self,
+                            cs: &'cs #krate::CriticalSection,
+                        ) -> &'cs #device::#name {
+                            unsafe { #name.borrow(cs) }
+                        }
+
+                        pub fn claim<R, F>(
+                            &self,
+                            t: &mut #krate::Threshold,
+                            f: F,
+                        ) -> R
+                        where
+                            F: FnOnce(
+                                &#device::#name,
+                                &mut #krate::Threshold) -> R
+                        {
+                            unsafe {
+                                #name.claim(
+                                    #ceiling,
+                                    #device::NVIC_PRIO_BITS,
+                                    t,
+                                    f,
+                                )
+                            }
+                        }
+                    });
+                }
+
+                impls.push(quote! {
+                    #[allow(dead_code)]
+                    impl _resource::#name {
+                        #(#impl_items)*
+                    }
+                });
+
+                items.push(quote! {
+                    #[allow(non_camel_case_types)]
+                    pub struct #name { _0: () }
+
+                    impl #name {
+                        pub unsafe fn new() -> Self {
+                            #name { _0: () }
+                        }
+                    }
+                });
+            }
+        }
+    }
+
+    root.push(quote! {
+        mod _resource {
+            #(#items)*
+        }
+
+        #(#impls)*
+    });
+}
+
+fn tasks(app: &App, ownerships: &Ownerships, root: &mut Vec<Tokens>) {
+    let device = &app.device;
     let krate = krate();
 
     for (name, task) in &app.tasks {
@@ -313,12 +476,11 @@ fn tasks(app: &App, ceilings: &Ceilings, root: &mut Vec<Tokens>) {
         let mut fields = vec![];
         let mut items = vec![];
 
-        let device = &app.device;
         let mut lifetime = None;
         let mut needs_reexport = false;
         for name in &task.resources {
-            match ceilings[name] {
-                Ceiling::Shared(ceiling) if ceiling > task.priority => {
+            match ownerships[name] {
+                Ownership::Shared { ceiling } if ceiling > task.priority => {
                     fields.push(quote! {
                         pub #name: super::_resource::#name,
                     });
@@ -405,169 +567,5 @@ fn tasks(app: &App, ceilings: &Ceilings, root: &mut Vec<Tokens>) {
                 #(#items)*
             }
         });
-
     }
 }
-
-fn resources(app: &App, ceilings: &Ceilings, root: &mut Vec<Tokens>) {
-    let krate = krate();
-    let device = &app.device;
-
-    let mut items = vec![];
-    let mut impls = vec![];
-    for (name, ceiling) in ceilings {
-        let mut impl_items = vec![];
-
-        match *ceiling {
-            Ceiling::Owned(_) => {
-                if let Some(resource) = app.resources.get(name) {
-                    // For owned resources we don't need claim() or borrow(),
-                    // just get()
-                    let expr = &resource.expr;
-                    let ty = &resource.ty;
-
-                    root.push(quote! {
-                        static #name: #krate::Resource<#ty> =
-                            #krate::Resource::new(#expr);
-                    });
-                } else {
-                    // Peripheral
-                    continue
-                }
-            },
-            Ceiling::Shared(ceiling) => {
-                if let Some(resource) = app.resources.get(name) {
-                    let expr = &resource.expr;
-                    let ty = &resource.ty;
-
-                    root.push(quote! {
-                        static #name: #krate::Resource<#ty> =
-                            #krate::Resource::new(#expr);
-                    });
-
-                    impl_items.push(quote! {
-                        pub fn borrow<'cs>(
-                            &'cs self,
-                            _cs: &'cs #krate::CriticalSection,
-                        ) -> &'cs #krate::Static<#ty> {
-                            unsafe {
-                                #krate::Static::ref_(&*#name.get())
-                            }
-                        }
-
-                        pub fn borrow_mut<'cs>(
-                            &'cs mut self,
-                            _cs: &'cs #krate::CriticalSection,
-                        ) -> &'cs mut #krate::Static<#ty> {
-                            unsafe {
-                                #krate::Static::ref_mut(&mut *#name.get())
-                            }
-                        }
-
-                        pub fn claim<R, F>(
-                            &self,
-                            t: &mut #krate::Threshold,
-                            f: F,
-                        ) -> R
-                        where
-                            F: FnOnce(
-                                &#krate::Static<#ty>,
-                                &mut #krate::Threshold) -> R
-                        {
-                            unsafe {
-                                #name.claim(
-                                    #ceiling,
-                                    #device::NVIC_PRIO_BITS,
-                                    t,
-                                    f,
-                                )
-                            }
-                        }
-
-                        pub fn claim_mut<R, F>(
-                            &mut self,
-                            t: &mut #krate::Threshold,
-                            f: F,
-                        ) -> R
-                        where
-                            F: FnOnce(
-                                &mut #krate::Static<#ty>,
-                                &mut #krate::Threshold) -> R
-                        {
-                            unsafe {
-                                #name.claim_mut(
-                                    #ceiling,
-                                    #device::NVIC_PRIO_BITS,
-                                    t,
-                                    f,
-                                )
-                            }
-                        }
-                    });
-                } else {
-                    root.push(quote! {
-                        static #name: #krate::Peripheral<#device::#name> =
-                            #krate::Peripheral::new(#device::#name);
-                    });
-
-                    impl_items.push(quote! {
-                        pub fn borrow<'cs>(
-                            &'cs self,
-                            _cs: &'cs #krate::CriticalSection,
-                        ) -> &'cs #device::#name {
-                            unsafe {
-                                &*#name.get()
-                            }
-                        }
-
-                        pub fn claim<R, F>(
-                            &self,
-                            t: &mut #krate::Threshold,
-                            f: F,
-                        ) -> R
-                        where
-                            F: FnOnce(
-                                &#device::#name,
-                                &mut #krate::Threshold) -> R
-                        {
-                            unsafe {
-                                #name.claim(
-                                    #ceiling,
-                                    #device::NVIC_PRIO_BITS,
-                                    t,
-                                    f,
-                                )
-                            }
-                        }
-                    });
-                }
-
-                impls.push(quote! {
-                    #[allow(dead_code)]
-                    impl _resource::#name {
-                        #(#impl_items)*
-                    }
-                });
-
-                items.push(quote! {
-                    #[allow(non_camel_case_types)]
-                    pub struct #name { _0: () }
-
-                    impl #name {
-                        pub unsafe fn new() -> Self {
-                            #name { _0: () }
-                        }
-                    }
-                });
-            }
-        }
-    }
-
-    root.push(quote! {
-        mod _resource {
-            #(#items)*
-        }
-
-        #(#impls)*
-    });
-}
diff --git a/macros/src/util.rs b/macros/src/util.rs
deleted file mode 100644
index 4722ca7de6..0000000000
--- a/macros/src/util.rs
+++ /dev/null
@@ -1,62 +0,0 @@
-use std::cmp;
-use std::collections::HashMap;
-
-use syn::Ident;
-
-use syntax::App;
-
-pub type Ceilings = HashMap<Ident, Ceiling>;
-
-#[derive(Clone, Copy, Debug, PartialEq)]
-pub enum Ceiling {
-    // Owned by one or more tasks that have the same priority
-    Owned(u8),
-    // Shared by tasks with different priorities
-    Shared(u8),
-}
-
-impl Ceiling {
-    pub fn is_owned(&self) -> bool {
-        match *self {
-            Ceiling::Owned(_) => true,
-            _ => false,
-        }
-    }
-}
-
-pub fn compute_ceilings(app: &App) -> Ceilings {
-    let mut ceilings = HashMap::new();
-
-    for resource in &app.idle.resources {
-        ceilings.insert(resource.clone(), Ceiling::Owned(0));
-    }
-
-    for task in app.tasks.values() {
-        for resource in &task.resources {
-            if let Some(ceiling) = ceilings.get_mut(resource) {
-                match *ceiling {
-                    Ceiling::Owned(current) => {
-                        if current == task.priority {
-                            *ceiling = Ceiling::Owned(current);
-                        } else {
-                            *ceiling = Ceiling::Shared(
-                                cmp::max(current, task.priority),
-                            );
-                        }
-                    }
-                    Ceiling::Shared(old) => {
-                        if task.priority > old {
-                            *ceiling = Ceiling::Shared(task.priority);
-                        }
-                    }
-                }
-
-                continue;
-            }
-
-            ceilings.insert(resource.clone(), Ceiling::Owned(task.priority));
-        }
-    }
-
-    ceilings
-}
diff --git a/src/lib.rs b/src/lib.rs
index 23f3abd1c5..daca2d0d8e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -82,6 +82,14 @@ impl<P> Peripheral<P> {
         Peripheral { peripheral }
     }
 
+    #[inline(always)]
+    pub unsafe fn borrow<'cs>(
+        &'static self,
+        _cs: &'cs CriticalSection,
+    ) -> &'cs P {
+        &*self.peripheral.get()
+    }
+
     #[inline(always)]
     pub unsafe fn claim<R, F>(
         &'static self,
@@ -123,7 +131,25 @@ pub struct Resource<T> {
 
 impl<T> Resource<T> {
     pub const fn new(value: T) -> Self {
-        Resource { data: UnsafeCell::new(value) }
+        Resource {
+            data: UnsafeCell::new(value),
+        }
+    }
+
+    #[inline(always)]
+    pub unsafe fn borrow<'cs>(
+        &'static self,
+        _cs: &'cs CriticalSection,
+    ) -> &'cs Static<T> {
+        Static::ref_(&*self.data.get())
+    }
+
+    #[inline(always)]
+    pub unsafe fn borrow_mut<'cs>(
+        &'static self,
+        _cs: &'cs CriticalSection,
+    ) -> &'cs mut Static<T> {
+        Static::ref_mut(&mut *self.data.get())
     }
 
     #[inline(always)]