diff --git a/embassy-extras/src/macros.rs b/embassy-extras/src/macros.rs
index e57b89ec7..5ce14a76d 100644
--- a/embassy-extras/src/macros.rs
+++ b/embassy-extras/src/macros.rs
@@ -122,7 +122,7 @@ macro_rules! std_peripherals {
 
         impl Peripherals {
             pub fn take() -> Option<(Peripherals, Clocks)> {
-                match unsafe {GLOBAL_CLOCKS} {
+                match unsafe {GLOBAL_CLOCKS.take()} {
                     Some(clocks) => {
                         let dp = unsafe { pac::Peripherals::steal() };
                         let peripherals = Peripherals {
diff --git a/embassy-macros/src/chip/stm32.rs b/embassy-macros/src/chip/stm32.rs
index 01c6a9cfd..e94c21a97 100644
--- a/embassy-macros/src/chip/stm32.rs
+++ b/embassy-macros/src/chip/stm32.rs
@@ -11,6 +11,8 @@ pub struct Args {
     pub sysclk: Option<u32>,
     #[darling(default)]
     pub pclk1: Option<u32>,
+    #[darling(default)]
+    pub require_pll48clk: bool,
 }
 
 pub fn generate(args: Args) -> TokenStream {
@@ -30,6 +32,10 @@ pub fn generate(args: Args) -> TokenStream {
         clock_cfg_args = quote! { #clock_cfg_args.pclk1(#mhz.mhz()) };
     }
 
+    if args.require_pll48clk {
+        clock_cfg_args = quote! { #clock_cfg_args.require_pll48clk() };
+    }
+
     quote!(
         use embassy_stm32::{rtc, interrupt, Peripherals, pac, hal::rcc::RccExt, hal::time::U32Ext};
 
diff --git a/embassy-stm32f4-examples/src/bin/serial.rs b/embassy-stm32f4-examples/src/bin/serial.rs
index 925fd68ff..1717cadb9 100644
--- a/embassy-stm32f4-examples/src/bin/serial.rs
+++ b/embassy-stm32f4-examples/src/bin/serial.rs
@@ -11,7 +11,7 @@ use example_common::{panic, *};
 
 use cortex_m::singleton;
 use cortex_m_rt::entry;
-use embassy::executor::Executor;
+use embassy::executor::{Executor, Spawner};
 use embassy::traits::uart::{Read, Write};
 use embassy::util::Forever;
 use embassy_stm32f4::interrupt;
@@ -22,26 +22,19 @@ use stm32f4xx_hal::prelude::*;
 use stm32f4xx_hal::serial::config::Config;
 use stm32f4xx_hal::stm32;
 
-#[embassy::task]
-async fn run(dp: stm32::Peripherals, _cp: cortex_m::Peripherals) {
+#[embassy::main(use_hse = 16, sysclk = 48, pclk1 = 24)]
+async fn main(spawner: Spawner) {
+    let (dp, clocks) = embassy_stm32::Peripherals::take().unwrap();
+    let cp = cortex_m::peripheral::Peripherals::take().unwrap();
+
     dp.DBGMCU.cr.modify(|_, w| {
         w.dbg_sleep().set_bit();
         w.dbg_standby().set_bit();
         w.dbg_stop().set_bit()
     });
-    dp.RCC.ahb1enr.modify(|_, w| w.dma1en().enabled());
 
     // https://gist.github.com/thalesfragoso/a07340c5df6eee3b04c42fdc69ecdcb1
     let gpioa = dp.GPIOA.split();
-    let rcc = dp.RCC.constrain();
-
-    let clocks = rcc
-        .cfgr
-        .use_hse(16.mhz())
-        .sysclk(48.mhz())
-        .pclk1(24.mhz())
-        .freeze();
-
     let streams = StreamsTuple::new(dp.DMA2);
 
     let _serial = unsafe {
@@ -84,16 +77,3 @@ async fn run(dp: stm32::Peripherals, _cp: cortex_m::Peripherals) {
     buf[5] = 0x01;
     serial.write(buf).await.unwrap();
 }
-
-static EXECUTOR: Forever<Executor> = Forever::new();
-
-#[entry]
-fn main() -> ! {
-    let dp = stm32::Peripherals::take().unwrap();
-    let cp = cortex_m::peripheral::Peripherals::take().unwrap();
-
-    let executor = EXECUTOR.put(Executor::new());
-    executor.run(|spawner| {
-        unwrap!(spawner.spawn(run(dp, cp)));
-    });
-}
diff --git a/embassy-stm32f4-examples/src/bin/usb_serial.rs b/embassy-stm32f4-examples/src/bin/usb_serial.rs
index 6d3b2cc14..669d187d4 100644
--- a/embassy-stm32f4-examples/src/bin/usb_serial.rs
+++ b/embassy-stm32f4-examples/src/bin/usb_serial.rs
@@ -10,7 +10,7 @@ use example_common::*;
 
 use cortex_m_rt::entry;
 use defmt::panic;
-use embassy::executor::Executor;
+use embassy::executor::{Executor, Spawner};
 use embassy::interrupt::InterruptExt;
 use embassy::io::{AsyncBufReadExt, AsyncWriteExt};
 use embassy::time::{Duration, Timer};
@@ -90,42 +90,15 @@ async fn run1(bus: &'static mut UsbBusAllocator<UsbBus<USB>>) {
     }
 }
 
-static RTC: Forever<rtc::RTC<pac::TIM2>> = Forever::new();
-static ALARM: Forever<rtc::Alarm<pac::TIM2>> = Forever::new();
-static EXECUTOR: Forever<Executor> = Forever::new();
 static USB_BUS: Forever<UsbBusAllocator<UsbBus<USB>>> = Forever::new();
 
-#[entry]
-fn main() -> ! {
+#[embassy::main(use_hse = 25, sysclk = 48, require_pll48clk)]
+async fn main(spawner: Spawner) -> ! {
     static mut EP_MEMORY: [u32; 1024] = [0; 1024];
 
     info!("Hello World!");
 
-    let p = unwrap!(pac::Peripherals::take());
-
-    p.RCC.ahb1enr.modify(|_, w| w.dma1en().enabled());
-    let rcc = p.RCC.constrain();
-    let clocks = rcc
-        .cfgr
-        .use_hse(25.mhz())
-        .sysclk(48.mhz())
-        .require_pll48clk()
-        .freeze();
-
-    p.DBGMCU.cr.modify(|_, w| {
-        w.dbg_sleep().set_bit();
-        w.dbg_standby().set_bit();
-        w.dbg_stop().set_bit()
-    });
-
-    let rtc = RTC.put(rtc::RTC::new(p.TIM2, interrupt::take!(TIM2), clocks));
-    rtc.start();
-
-    unsafe { embassy::time::set_clock(rtc) };
-
-    let alarm = ALARM.put(rtc.alarm1());
-    let executor = EXECUTOR.put(Executor::new());
-    executor.set_alarm(alarm);
+    let (p, clocks) = embassy_stm32::Peripherals::take().unwrap();
 
     let gpioa = p.GPIOA.split();
     let usb = USB {
@@ -138,9 +111,7 @@ fn main() -> ! {
     };
     // Rust analyzer isn't recognizing the static ref magic `cortex-m` does
     #[allow(unused_unsafe)]
-    let usb_bus = USB_BUS.put(UsbBus::new(usb, unsafe { EP_MEMORY }));
+    let usb_bus = USB_BUS.put(UsbBus::new(usb, unsafe { &mut EP_MEMORY }));
 
-    executor.run(move |spawner| {
-        unwrap!(spawner.spawn(run1(usb_bus)));
-    });
+    spawner.spawn(run1(usb_bus)).unwrap();
 }