Add `init` fn. Initializes hw and returns Peripherals.

24 files changed, 217 insertions, 258 deletions

diff --git a/embassy-extras/src/macros.rs b/embassy-extras/src/macros.rs
index 860c0795a..fba752619 100644
--- a/embassy-extras/src/macros.rs
+++ b/embassy-extras/src/macros.rs
@@ -46,18 +46,17 @@ macro_rules! peripherals {
         impl Peripherals {
             ///Returns all the peripherals *once*
             #[inline]
-            pub fn take() -> Option<Self> {
+            pub(crate) fn take() -> Self {
 
                 #[no_mangle]
                 static mut _EMBASSY_DEVICE_PERIPHERALS: bool = false;
 
-                critical_section::with(|_| {
-                    if unsafe { _EMBASSY_DEVICE_PERIPHERALS } {
-                        None
-                    } else {
-                        unsafe { _EMBASSY_DEVICE_PERIPHERALS = true };
-                        Some(unsafe { <Self as embassy::util::Steal>::steal() })
+                critical_section::with(|_| unsafe {
+                    if _EMBASSY_DEVICE_PERIPHERALS {
+                        panic!("init called more than once!")
                     }
+                    _EMBASSY_DEVICE_PERIPHERALS = true;
+                    <Self as embassy::util::Steal>::steal()
                 })
             }
         }
diff --git a/embassy-macros/src/chip/nrf.rs b/embassy-macros/src/chip/nrf.rs
index aba4c004f..503a8ba5a 100644
--- a/embassy-macros/src/chip/nrf.rs
+++ b/embassy-macros/src/chip/nrf.rs
@@ -9,7 +9,7 @@ pub fn generate(embassy_prefix: &ModulePrefix, config: syn::Expr) -> TokenStream
     quote!(
         use #embassy_nrf_path::{interrupt, peripherals, rtc};
 
-        unsafe { #embassy_nrf_path::system::configure(#config) };
+        let p = #embassy_nrf_path::init(#config);
 
         let mut rtc = rtc::RTC::new(unsafe { <peripherals::RTC1 as #embassy_path::util::Steal>::steal() }, interrupt::take!(RTC1));
         let rtc = unsafe { make_static(&mut rtc) };
diff --git a/embassy-macros/src/chip/rp.rs b/embassy-macros/src/chip/rp.rs
index 33863de86..04211f8f3 100644
--- a/embassy-macros/src/chip/rp.rs
+++ b/embassy-macros/src/chip/rp.rs
@@ -7,6 +7,6 @@ pub fn generate(embassy_prefix: &ModulePrefix, config: syn::Expr) -> TokenStream
     quote!(
         use #embassy_rp_path::{interrupt, peripherals};
 
-        unsafe { #embassy_rp_path::system::configure(#config) };
+        let p = #embassy_rp_path::init(#config);
     )
 }
diff --git a/embassy-macros/src/lib.rs b/embassy-macros/src/lib.rs
index d91549ca7..dc234cd6d 100644
--- a/embassy-macros/src/lib.rs
+++ b/embassy-macros/src/lib.rs
@@ -315,12 +315,12 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
 
     let args = task_fn.sig.inputs.clone();
 
-    if args.len() != 1 {
+    if args.len() != 2 {
         task_fn
             .sig
             .span()
             .unwrap()
-            .error("main function must have one argument")
+            .error("main function must have 2 arguments")
             .emit();
         fail = true;
     }
@@ -364,7 +364,7 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
             #chip_setup
 
             executor.run(|spawner| {
-                spawner.spawn(__embassy_main(spawner)).unwrap();
+                spawner.spawn(__embassy_main(spawner, p)).unwrap();
             })
 
         }
diff --git a/embassy-nrf-examples/src/bin/blinky.rs b/embassy-nrf-examples/src/bin/blinky.rs
index 4cb09bee7..e6fc854b5 100644
--- a/embassy-nrf-examples/src/bin/blinky.rs
+++ b/embassy-nrf-examples/src/bin/blinky.rs
@@ -17,8 +17,7 @@ use embassy_nrf::Peripherals;
 use embedded_hal::digital::v2::OutputPin;
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = Peripherals::take().unwrap();
+async fn main(spawner: Spawner, p: Peripherals) {
     let mut led = Output::new(p.P0_13, Level::Low, OutputDrive::Standard);
 
     loop {
diff --git a/embassy-nrf-examples/src/bin/buffered_uart.rs b/embassy-nrf-examples/src/bin/buffered_uart.rs
index 8f5d9fb2e..b3a621c6b 100644
--- a/embassy-nrf-examples/src/bin/buffered_uart.rs
+++ b/embassy-nrf-examples/src/bin/buffered_uart.rs
@@ -17,9 +17,7 @@ use example_common::*;
 use futures::pin_mut;
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = Peripherals::take().unwrap();
-
+async fn main(spawner: Spawner, p: Peripherals) {
     let mut config = uarte::Config::default();
     config.parity = uarte::Parity::EXCLUDED;
     config.baudrate = uarte::Baudrate::BAUD115200;
diff --git a/embassy-nrf-examples/src/bin/executor_fairness_test.rs b/embassy-nrf-examples/src/bin/executor_fairness_test.rs
index 3ea74316e..ca9bcc1e6 100644
--- a/embassy-nrf-examples/src/bin/executor_fairness_test.rs
+++ b/embassy-nrf-examples/src/bin/executor_fairness_test.rs
@@ -13,7 +13,7 @@ use core::task::Poll;
 use defmt::panic;
 use embassy::executor::Spawner;
 use embassy::time::{Duration, Instant, Timer};
-use embassy_nrf::interrupt;
+use embassy_nrf::{interrupt, Peripherals};
 
 #[embassy::task]
 async fn run1() {
@@ -40,7 +40,7 @@ async fn run3() {
 }
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
+async fn main(spawner: Spawner, p: Peripherals) {
     unwrap!(spawner.spawn(run1()));
     unwrap!(spawner.spawn(run2()));
     unwrap!(spawner.spawn(run3()));
diff --git a/embassy-nrf-examples/src/bin/gpiote_channel.rs b/embassy-nrf-examples/src/bin/gpiote_channel.rs
index ee670acd5..d52ed7767 100644
--- a/embassy-nrf-examples/src/bin/gpiote_channel.rs
+++ b/embassy-nrf-examples/src/bin/gpiote_channel.rs
@@ -12,13 +12,11 @@ use example_common::*;
 use defmt::panic;
 use embassy::executor::Spawner;
 use embassy_nrf::gpio::{Input, Pull};
-use embassy_nrf::gpiote::{self, InputChannel, InputChannelPolarity};
+use embassy_nrf::gpiote::{InputChannel, InputChannelPolarity};
 use embassy_nrf::{interrupt, Peripherals};
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = Peripherals::take().unwrap();
-
+async fn main(spawner: Spawner, p: Peripherals) {
     info!("Starting!");
 
     let ch1 = InputChannel::new(
diff --git a/embassy-nrf-examples/src/bin/gpiote_port.rs b/embassy-nrf-examples/src/bin/gpiote_port.rs
index 717d3398b..4a7951cd3 100644
--- a/embassy-nrf-examples/src/bin/gpiote_port.rs
+++ b/embassy-nrf-examples/src/bin/gpiote_port.rs
@@ -28,9 +28,7 @@ async fn button_task(n: usize, mut pin: PortInput<'static, AnyPin>) {
 }
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = Peripherals::take().unwrap();
-
+async fn main(spawner: Spawner, p: Peripherals) {
     info!("Starting!");
 
     let btn1 = PortInput::new(Input::new(p.P0_11.degrade(), Pull::Up));
diff --git a/embassy-nrf-examples/src/bin/multiprio.rs b/embassy-nrf-examples/src/bin/multiprio.rs
index 9ed5c1368..79fa029b3 100644
--- a/embassy-nrf-examples/src/bin/multiprio.rs
+++ b/embassy-nrf-examples/src/bin/multiprio.rs
@@ -126,9 +126,8 @@ static EXECUTOR_LOW: Forever<Executor> = Forever::new();
 fn main() -> ! {
     info!("Hello World!");
 
-    let p = unwrap!(embassy_nrf::Peripherals::take());
+    let p = embassy_nrf::init(Default::default());
 
-    unsafe { embassy_nrf::system::configure(Default::default()) };
     let rtc = RTC.put(rtc::RTC::new(p.RTC1, interrupt::take!(RTC1)));
     rtc.start();
     unsafe { embassy::time::set_clock(rtc) };
diff --git a/embassy-nrf-examples/src/bin/ppi.rs b/embassy-nrf-examples/src/bin/ppi.rs
index 3c39e032e..47782ed29 100644
--- a/embassy-nrf-examples/src/bin/ppi.rs
+++ b/embassy-nrf-examples/src/bin/ppi.rs
@@ -19,9 +19,7 @@ use embassy_nrf::{interrupt, Peripherals};
 use gpiote::{OutputChannel, OutputChannelPolarity};
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = Peripherals::take().unwrap();
-
+async fn main(spawner: Spawner, p: Peripherals) {
     info!("Starting!");
 
     let button1 = InputChannel::new(
diff --git a/embassy-nrf-examples/src/bin/qspi.rs b/embassy-nrf-examples/src/bin/qspi.rs
index 28cde6e51..3dc027f6f 100644
--- a/embassy-nrf-examples/src/bin/qspi.rs
+++ b/embassy-nrf-examples/src/bin/qspi.rs
@@ -23,9 +23,7 @@ const PAGE_SIZE: usize = 4096;
 struct AlignedBuf([u8; 4096]);
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = Peripherals::take().unwrap();
-
+async fn main(spawner: Spawner, p: Peripherals) {
     let csn = p.P0_17;
     let sck = p.P0_19;
     let io0 = p.P0_20;
diff --git a/embassy-nrf-examples/src/bin/raw_spawn.rs b/embassy-nrf-examples/src/bin/raw_spawn.rs
index f8e021d9b..78de7b100 100644
--- a/embassy-nrf-examples/src/bin/raw_spawn.rs
+++ b/embassy-nrf-examples/src/bin/raw_spawn.rs
@@ -37,9 +37,8 @@ static EXECUTOR: Forever<Executor> = Forever::new();
 fn main() -> ! {
     info!("Hello World!");
 
-    let p = unwrap!(embassy_nrf::Peripherals::take());
+    let p = embassy_nrf::init(Default::default());
 
-    unsafe { embassy_nrf::system::configure(Default::default()) };
     let rtc = RTC.put(rtc::RTC::new(p.RTC1, interrupt::take!(RTC1)));
     rtc.start();
     unsafe { embassy::time::set_clock(rtc) };
diff --git a/embassy-nrf-examples/src/bin/spim.rs b/embassy-nrf-examples/src/bin/spim.rs
index ccda75765..df921fc86 100644
--- a/embassy-nrf-examples/src/bin/spim.rs
+++ b/embassy-nrf-examples/src/bin/spim.rs
@@ -19,11 +19,9 @@ use embedded_hal::digital::v2::*;
 use example_common::*;
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
+async fn main(spawner: Spawner, p: Peripherals) {
     info!("running!");
 
-    let p = unsafe { Peripherals::steal() };
-
     let mut config = spim::Config::default();
     config.frequency = spim::Frequency::M16;
 
diff --git a/embassy-nrf-examples/src/bin/timer.rs b/embassy-nrf-examples/src/bin/timer.rs
index a2b717bc1..ffbbb7841 100644
--- a/embassy-nrf-examples/src/bin/timer.rs
+++ b/embassy-nrf-examples/src/bin/timer.rs
@@ -7,6 +7,7 @@
 
 #[path = "../example_common.rs"]
 mod example_common;
+use embassy_nrf::Peripherals;
 use example_common::*;
 
 use defmt::panic;
@@ -30,7 +31,7 @@ async fn run2() {
 }
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
+async fn main(spawner: Spawner, p: Peripherals) {
     unwrap!(spawner.spawn(run1()));
     unwrap!(spawner.spawn(run2()));
 }
diff --git a/embassy-nrf-examples/src/bin/uart.rs b/embassy-nrf-examples/src/bin/uart.rs
index 23fc89312..9a0e65d3e 100644
--- a/embassy-nrf-examples/src/bin/uart.rs
+++ b/embassy-nrf-examples/src/bin/uart.rs
@@ -17,9 +17,7 @@ use embassy_nrf::gpio::NoPin;
 use embassy_nrf::{interrupt, uarte, Peripherals};
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = unsafe { Peripherals::steal() };
-
+async fn main(spawner: Spawner, p: Peripherals) {
     let mut config = uarte::Config::default();
     config.parity = uarte::Parity::EXCLUDED;
     config.baudrate = uarte::Baudrate::BAUD115200;
@@ -42,33 +40,5 @@ async fn main(spawner: Spawner) {
         unwrap!(uart.read(&mut buf).await);
         info!("writing...");
         unwrap!(uart.write(&buf).await);
-
-        /*
-        // `receive()` doesn't return until the buffer has been completely filled with
-        // incoming data, which in this case is 8 bytes.
-        //
-        // This example shows how to use `select` to run an uart receive concurrently with a
-        // 1 second timer, effectively adding a timeout to the receive operation.
-        let recv_fut = uart.read(&mut buf);
-        let timer_fut = Timer::after(Duration::from_millis(1000));
-        let received_len = match select(recv_fut, timer_fut).await {
-            // recv_fut completed first, so we've received `buf_len` bytes.
-            Either::Left(_) => buf_len,
-            // timer_fut completed first. `select` gives us back the future that didn't complete, which
-            // is `recv_fut` in this case, so we can do further stuff with it.
-            //
-            // The recv_fut would stop the uart read automatically when dropped. However, we want to know how
-            // many bytes have been received, so we have to "gracefully stop" it with `.stop()`.
-            Either::Right((_, recv_fut)) => recv_fut.stop().await,
-        };
-        let received = &mut buf[..received_len];
-
-        if !received.is_empty() {
-            info!("read done, got {}", received);
-
-            // Echo back received data
-            unwrap!(uart.write(received).await);
-        }
-         */
     }
 }
diff --git a/embassy-nrf-examples/src/bin/uart_idle.rs b/embassy-nrf-examples/src/bin/uart_idle.rs
index 54d524ae5..a97c65933 100644
--- a/embassy-nrf-examples/src/bin/uart_idle.rs
+++ b/embassy-nrf-examples/src/bin/uart_idle.rs
@@ -18,9 +18,7 @@ use embassy_nrf::gpio::NoPin;
 use embassy_nrf::{interrupt, uarte, Peripherals};
 
 #[embassy::main]
-async fn main(spawner: Spawner) {
-    let p = unsafe { Peripherals::steal() };
-
+async fn main(spawner: Spawner, p: Peripherals) {
     let mut config = uarte::Config::default();
     config.parity = uarte::Parity::EXCLUDED;
     config.baudrate = uarte::Baudrate::BAUD115200;
diff --git a/embassy-nrf/src/lib.rs b/embassy-nrf/src/lib.rs
index 4349bf39f..6ab9cbb27 100644
--- a/embassy-nrf/src/lib.rs
+++ b/embassy-nrf/src/lib.rs
@@ -35,7 +35,6 @@ pub mod rtc;
 #[cfg(not(feature = "nrf52820"))]
 pub mod saadc;
 pub mod spim;
-pub mod system;
 pub mod timer;
 pub mod twim;
 pub mod uarte;
@@ -73,3 +72,88 @@ pub mod interrupt {
     pub use embassy_extras::interrupt::Priority3 as Priority;
 }
 pub use embassy_macros::interrupt;
+
+pub mod config {
+    pub enum HfclkSource {
+        Internal,
+        ExternalXtal,
+    }
+
+    pub enum LfclkSource {
+        InternalRC,
+        Synthesized,
+        ExternalXtal,
+        ExternalLowSwing,
+        ExternalFullSwing,
+    }
+
+    #[non_exhaustive]
+    pub struct Config {
+        pub hfclk_source: HfclkSource,
+        pub lfclk_source: LfclkSource,
+    }
+
+    impl Default for Config {
+        fn default() -> Self {
+            Self {
+                // There are hobby nrf52 boards out there without external XTALs...
+                // Default everything to internal so it Just Works. User can enable external
+                // xtals if they know they have them.
+                hfclk_source: HfclkSource::Internal,
+                lfclk_source: LfclkSource::InternalRC,
+            }
+        }
+    }
+}
+
+pub fn init(config: config::Config) -> Peripherals {
+    // Do this first, so that it panics if user is calling `init` a second time
+    // before doing anything important.
+    let peripherals = Peripherals::take();
+
+    let r = unsafe { &*pac::CLOCK::ptr() };
+
+    // Start HFCLK.
+    match config.hfclk_source {
+        config::HfclkSource::Internal => {}
+        config::HfclkSource::ExternalXtal => {
+            // Datasheet says this is likely to take 0.36ms
+            r.events_hfclkstarted.write(|w| unsafe { w.bits(0) });
+            r.tasks_hfclkstart.write(|w| unsafe { w.bits(1) });
+            while r.events_hfclkstarted.read().bits() == 0 {}
+        }
+    }
+
+    // Configure LFCLK.
+    match config.lfclk_source {
+        config::LfclkSource::InternalRC => r.lfclksrc.write(|w| w.src().rc()),
+        config::LfclkSource::Synthesized => r.lfclksrc.write(|w| w.src().synth()),
+
+        config::LfclkSource::ExternalXtal => r.lfclksrc.write(|w| w.src().xtal()),
+
+        config::LfclkSource::ExternalLowSwing => r.lfclksrc.write(|w| {
+            w.src().xtal();
+            w.external().enabled();
+            w.bypass().disabled();
+            w
+        }),
+        config::LfclkSource::ExternalFullSwing => r.lfclksrc.write(|w| {
+            w.src().xtal();
+            w.external().enabled();
+            w.bypass().enabled();
+            w
+        }),
+    }
+
+    // Start LFCLK.
+    // Datasheet says this could take 100us from synth source
+    // 600us from rc source, 0.25s from an external source.
+    r.events_lfclkstarted.write(|w| unsafe { w.bits(0) });
+    r.tasks_lfclkstart.write(|w| unsafe { w.bits(1) });
+    while r.events_lfclkstarted.read().bits() == 0 {}
+
+    // Init GPIOTE
+    crate::gpiote::init();
+
+    peripherals
+}
diff --git a/embassy-nrf/src/system.rs b/embassy-nrf/src/system.rs
deleted file mode 100644
index e358d2c38..000000000
--- a/embassy-nrf/src/system.rs
+++ /dev/null
@@ -1,79 +0,0 @@
-use crate::pac;
-
-pub enum HfclkSource {
-    Internal,
-    ExternalXtal,
-}
-
-pub enum LfclkSource {
-    InternalRC,
-    Synthesized,
-    ExternalXtal,
-    ExternalLowSwing,
-    ExternalFullSwing,
-}
-
-#[non_exhaustive]
-pub struct Config {
-    pub hfclk_source: HfclkSource,
-    pub lfclk_source: LfclkSource,
-}
-
-impl Default for Config {
-    fn default() -> Self {
-        Self {
-            // There are hobby nrf52 boards out there without external XTALs...
-            // Default everything to internal so it Just Works. User can enable external
-            // xtals if they know they have them.
-            hfclk_source: HfclkSource::Internal,
-            lfclk_source: LfclkSource::InternalRC,
-        }
-    }
-}
-
-/// safety: must only call once.
-pub unsafe fn configure(config: Config) {
-    let r = &*pac::CLOCK::ptr();
-
-    // Start HFCLK.
-    match config.hfclk_source {
-        HfclkSource::Internal => {}
-        HfclkSource::ExternalXtal => {
-            // Datasheet says this is likely to take 0.36ms
-            r.events_hfclkstarted.write(|w| unsafe { w.bits(0) });
-            r.tasks_hfclkstart.write(|w| unsafe { w.bits(1) });
-            while r.events_hfclkstarted.read().bits() == 0 {}
-        }
-    }
-
-    // Configure LFCLK.
-    match config.lfclk_source {
-        LfclkSource::InternalRC => r.lfclksrc.write(|w| w.src().rc()),
-        LfclkSource::Synthesized => r.lfclksrc.write(|w| w.src().synth()),
-
-        LfclkSource::ExternalXtal => r.lfclksrc.write(move |w| w.src().xtal()),
-
-        LfclkSource::ExternalLowSwing => r.lfclksrc.write(move |w| {
-            w.src().xtal();
-            w.external().enabled();
-            w.bypass().disabled();
-            w
-        }),
-        LfclkSource::ExternalFullSwing => r.lfclksrc.write(move |w| {
-            w.src().xtal();
-            w.external().enabled();
-            w.bypass().enabled();
-            w
-        }),
-    }
-
-    // Start LFCLK.
-    // Datasheet says this could take 100us from synth source
-    // 600us from rc source, 0.25s from an external source.
-    r.events_lfclkstarted.write(|w| unsafe { w.bits(0) });
-    r.tasks_lfclkstart.write(|w| unsafe { w.bits(1) });
-    while r.events_lfclkstarted.read().bits() == 0 {}
-
-    // Init GPIOTE
-    crate::gpiote::init();
-}
diff --git a/embassy-rp-examples/src/bin/blinky.rs b/embassy-rp-examples/src/bin/blinky.rs
index 34e3cafc3..e42999912 100644
--- a/embassy-rp-examples/src/bin/blinky.rs
+++ b/embassy-rp-examples/src/bin/blinky.rs
@@ -16,9 +16,7 @@ use embedded_hal::digital::v2::OutputPin;
 use gpio::{Level, Output};
 
 #[embassy::main]
-async fn main(_spawner: Spawner) {
-    let p = unwrap!(Peripherals::take());
-
+async fn main(_spawner: Spawner, p: Peripherals) {
     let mut led = Output::new(p.PIN_25, Level::Low);
 
     loop {
diff --git a/embassy-rp-examples/src/bin/button.rs b/embassy-rp-examples/src/bin/button.rs
index 77d4c57a9..007d07a36 100644
--- a/embassy-rp-examples/src/bin/button.rs
+++ b/embassy-rp-examples/src/bin/button.rs
@@ -16,9 +16,7 @@ use embassy_rp::Peripherals;
 use embedded_hal::digital::v2::{InputPin, OutputPin};
 
 #[embassy::main]
-async fn main(_spawner: Spawner) {
-    let p = unwrap!(Peripherals::take());
-
+async fn main(_spawner: Spawner, p: Peripherals) {
     let button = Input::new(p.PIN_28, Pull::Up);
     let mut led = Output::new(p.PIN_25, Level::Low);
 
diff --git a/embassy-rp-examples/src/bin/uart.rs b/embassy-rp-examples/src/bin/uart.rs
index cd72d5312..82bd4cb6a 100644
--- a/embassy-rp-examples/src/bin/uart.rs
+++ b/embassy-rp-examples/src/bin/uart.rs
@@ -14,9 +14,7 @@ use embassy::executor::Spawner;
 use embassy_rp::{uart, Peripherals};
 
 #[embassy::main]
-async fn main(_spanwer: Spawner) {
-    let p = unwrap!(Peripherals::take());
-
+async fn main(_spawner: Spawner, p: Peripherals) {
     let config = uart::Config::default();
     let mut uart = uart::Uart::new(p.UART0, p.PIN_0, p.PIN_1, p.PIN_2, p.PIN_3, config);
     uart.send("Hello World!\r\n".as_bytes());
diff --git a/embassy-rp/src/lib.rs b/embassy-rp/src/lib.rs
index f64464d13..f1a045987 100644
--- a/embassy-rp/src/lib.rs
+++ b/embassy-rp/src/lib.rs
@@ -15,7 +15,6 @@ pub mod dma;
 pub mod gpio;
 pub mod pll;
 pub mod resets;
-pub mod system;
 pub mod uart;
 
 embassy_extras::peripherals! {
@@ -72,3 +71,105 @@ embassy_extras::peripherals! {
     DMA_CH10,
     DMA_CH11,
 }
+
+#[link_section = ".boot2"]
+#[used]
+static BOOT2: [u8; 256] = *include_bytes!("boot2.bin");
+
+pub mod config {
+    #[non_exhaustive]
+    pub struct Config {}
+
+    impl Default for Config {
+        fn default() -> Self {
+            Self {}
+        }
+    }
+}
+
+pub fn init(config: config::Config) -> Peripherals {
+    // Do this first, so that it panics if user is calling `init` a second time
+    // before doing anything important.
+    let peripherals = Peripherals::take();
+
+    // Now reset all the peripherals, except QSPI and XIP (we're using those
+    // to execute from external flash!)
+
+    let resets = resets::Resets::new();
+
+    // Reset everything except:
+    // - QSPI (we're using it to run this code!)
+    // - PLLs (it may be suicide if that's what's clocking us)
+    let mut peris = resets::ALL_PERIPHERALS;
+    peris.set_io_qspi(false);
+    peris.set_pads_qspi(false);
+    peris.set_pll_sys(false);
+    peris.set_pll_usb(false);
+    resets.reset(peris);
+
+    let mut peris = resets::ALL_PERIPHERALS;
+    peris.set_adc(false);
+    peris.set_rtc(false);
+    peris.set_spi0(false);
+    peris.set_spi1(false);
+    peris.set_uart0(false);
+    peris.set_uart1(false);
+    peris.set_usbctrl(false);
+    resets.unreset_wait(peris);
+
+    unsafe {
+        // xosc 12 mhz
+        pac::WATCHDOG.tick().write(|w| {
+            w.set_cycles(XOSC_MHZ as u16);
+            w.set_enable(true);
+        });
+
+        pac::CLOCKS
+            .clk_sys_resus_ctrl()
+            .write_value(pac::clocks::regs::ClkSysResusCtrl(0));
+
+        // Enable XOSC
+        // TODO extract to HAL module
+        const XOSC_MHZ: u32 = 12;
+        pac::XOSC
+            .ctrl()
+            .write(|w| w.set_freq_range(pac::xosc::vals::CtrlFreqRange::_1_15MHZ));
+
+        let startup_delay = (((XOSC_MHZ * 1_000_000) / 1000) + 128) / 256;
+        pac::XOSC
+            .startup()
+            .write(|w| w.set_delay(startup_delay as u16));
+        pac::XOSC.ctrl().write(|w| {
+            w.set_freq_range(pac::xosc::vals::CtrlFreqRange::_1_15MHZ);
+            w.set_enable(pac::xosc::vals::CtrlEnable::ENABLE);
+        });
+        while !pac::XOSC.status().read().stable() {}
+
+        // Before we touch PLLs, switch sys and ref cleanly away from their aux sources.
+        pac::CLOCKS
+            .clk_sys_ctrl()
+            .modify(|w| w.set_src(pac::clocks::vals::ClkSysCtrlSrc::CLK_REF));
+        while pac::CLOCKS.clk_sys_selected().read() != 1 {}
+        pac::CLOCKS
+            .clk_ref_ctrl()
+            .modify(|w| w.set_src(pac::clocks::vals::ClkRefCtrlSrc::ROSC_CLKSRC_PH));
+        while pac::CLOCKS.clk_ref_selected().read() != 1 {}
+
+        let mut peris = resets::Peripherals(0);
+        peris.set_pll_sys(true);
+        peris.set_pll_usb(true);
+        resets.reset(peris);
+        resets.unreset_wait(peris);
+
+        pll::PLL::new(pll::PllSys).configure(1, 1500_000_000, 6, 2);
+        pll::PLL::new(pll::PllUsb).configure(1, 480_000_000, 5, 2);
+
+        // Activate peripheral clock and take external oscillator as input
+        pac::CLOCKS.clk_peri_ctrl().write(|w| {
+            w.set_enable(true);
+            w.set_auxsrc(pac::clocks::vals::ClkPeriCtrlAuxsrc::XOSC_CLKSRC);
+        });
+    }
+
+    peripherals
+}
diff --git a/embassy-rp/src/system.rs b/embassy-rp/src/system.rs
deleted file mode 100644
index ba1396433..000000000
--- a/embassy-rp/src/system.rs
+++ /dev/null
@@ -1,94 +0,0 @@
-use crate::{pac, pll, resets};
-
-#[link_section = ".boot2"]
-#[used]
-pub static BOOT2: [u8; 256] = *include_bytes!("boot2.bin");
-
-#[non_exhaustive]
-pub struct Config {}
-
-impl Default for Config {
-    fn default() -> Self {
-        Self {}
-    }
-}
-
-/// safety: must only call once.
-pub unsafe fn configure(_config: Config) {
-    // Now reset all the peripherals, except QSPI and XIP (we're using those
-    // to execute from external flash!)
-
-    let resets = resets::Resets::new();
-
-    // Reset everything except:
-    // - QSPI (we're using it to run this code!)
-    // - PLLs (it may be suicide if that's what's clocking us)
-    let mut peris = resets::ALL_PERIPHERALS;
-    peris.set_io_qspi(false);
-    peris.set_pads_qspi(false);
-    peris.set_pll_sys(false);
-    peris.set_pll_usb(false);
-    resets.reset(peris);
-
-    let mut peris = resets::ALL_PERIPHERALS;
-    peris.set_adc(false);
-    peris.set_rtc(false);
-    peris.set_spi0(false);
-    peris.set_spi1(false);
-    peris.set_uart0(false);
-    peris.set_uart1(false);
-    peris.set_usbctrl(false);
-    resets.unreset_wait(peris);
-
-    // xosc 12 mhz
-    pac::WATCHDOG.tick().write(|w| {
-        w.set_cycles(XOSC_MHZ as u16);
-        w.set_enable(true);
-    });
-
-    pac::CLOCKS
-        .clk_sys_resus_ctrl()
-        .write_value(pac::clocks::regs::ClkSysResusCtrl(0));
-
-    // Enable XOSC
-    // TODO extract to HAL module
-    const XOSC_MHZ: u32 = 12;
-    pac::XOSC
-        .ctrl()
-        .write(|w| w.set_freq_range(pac::xosc::vals::CtrlFreqRange::_1_15MHZ));
-
-    let startup_delay = (((XOSC_MHZ * 1_000_000) / 1000) + 128) / 256;
-    pac::XOSC
-        .startup()
-        .write(|w| w.set_delay(startup_delay as u16));
-    pac::XOSC.ctrl().write(|w| {
-        w.set_freq_range(pac::xosc::vals::CtrlFreqRange::_1_15MHZ);
-        w.set_enable(pac::xosc::vals::CtrlEnable::ENABLE);
-    });
-    while !pac::XOSC.status().read().stable() {}
-
-    // Before we touch PLLs, switch sys and ref cleanly away from their aux sources.
-    pac::CLOCKS
-        .clk_sys_ctrl()
-        .modify(|w| w.set_src(pac::clocks::vals::ClkSysCtrlSrc::CLK_REF));
-    while pac::CLOCKS.clk_sys_selected().read() != 1 {}
-    pac::CLOCKS
-        .clk_ref_ctrl()
-        .modify(|w| w.set_src(pac::clocks::vals::ClkRefCtrlSrc::ROSC_CLKSRC_PH));
-    while pac::CLOCKS.clk_ref_selected().read() != 1 {}
-
-    let mut peris = resets::Peripherals(0);
-    peris.set_pll_sys(true);
-    peris.set_pll_usb(true);
-    resets.reset(peris);
-    resets.unreset_wait(peris);
-
-    pll::PLL::new(pll::PllSys).configure(1, 1500_000_000, 6, 2);
-    pll::PLL::new(pll::PllUsb).configure(1, 480_000_000, 5, 2);
-
-    // Activate peripheral clock and take external oscillator as input
-    pac::CLOCKS.clk_peri_ctrl().write(|w| {
-        w.set_enable(true);
-        w.set_auxsrc(pac::clocks::vals::ClkPeriCtrlAuxsrc::XOSC_CLKSRC);
-    });
-}