diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index f4105230..fc836dfc 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -102,8 +102,15 @@ jobs:
         with:
           path: target
           key: ${{ runner.os }}-${{ matrix.target }}
+
+      # We have to append the "-D warnings" flag to .cargo/config rather than
+      # using the RUSTFLAGS environment variable because if we set RUSTFLAGS
+      # cargo will ignore the rustflags config in .cargo/config.
       - name: Check
-        run: cd ${{ matrix.package }} &&  cargo check --features=${{ matrix.features }} --target=${{ matrix.target }}
+        run: |
+          mkdir -p .cargo
+          echo -e '[target."cfg(all())"]\nrustflags = ["-D", "warnings"]' >> .cargo/config
+          cd ${{ matrix.package }} && RUSTFLAGS=-Dwarnings cargo check --features=${{ matrix.features }} --target=${{ matrix.target }}
 
   fmt:
     runs-on: ubuntu-latest
diff --git a/embassy-nrf/src/gpiote.rs b/embassy-nrf/src/gpiote.rs
index 2ef26e36..54d3dd01 100644
--- a/embassy-nrf/src/gpiote.rs
+++ b/embassy-nrf/src/gpiote.rs
@@ -10,7 +10,7 @@ use embedded_hal::digital::v2::{InputPin, StatefulOutputPin};
 use futures::future::poll_fn;
 
 use crate::gpio::sealed::Pin as _;
-use crate::gpio::{AnyPin, Input, Output, Pin as GpioPin, Port};
+use crate::gpio::{AnyPin, Input, Output, Pin as GpioPin};
 use crate::pac;
 use crate::ppi::{Event, Task};
 use crate::{interrupt, peripherals};
@@ -140,8 +140,8 @@ impl<'d, C: Channel, T: GpioPin> InputChannel<'d, C, T> {
             };
             #[cfg(any(feature = "nrf52833", feature = "nrf52840"))]
             w.port().bit(match pin.pin.port() {
-                Port::Port0 => false,
-                Port::Port1 => true,
+                crate::gpio::Port::Port0 => false,
+                crate::gpio::Port::Port1 => true,
             });
             unsafe { w.psel().bits(pin.pin.pin()) }
         });
@@ -223,8 +223,8 @@ impl<'d, C: Channel, T: GpioPin> OutputChannel<'d, C, T> {
             };
             #[cfg(any(feature = "nrf52833", feature = "nrf52840"))]
             w.port().bit(match pin.pin.port() {
-                Port::Port0 => false,
-                Port::Port1 => true,
+                crate::gpio::Port::Port0 => false,
+                crate::gpio::Port::Port1 => true,
             });
             unsafe { w.psel().bits(pin.pin.pin()) }
         });
diff --git a/embassy-stm32/src/adc/v3.rs b/embassy-stm32/src/adc/v3.rs
index 36af6ec4..7480c4a3 100644
--- a/embassy-stm32/src/adc/v3.rs
+++ b/embassy-stm32/src/adc/v3.rs
@@ -1,6 +1,5 @@
 use crate::adc::{AdcPin, Instance};
 use core::marker::PhantomData;
-use cortex_m::delay::Delay;
 use embassy::util::Unborrow;
 use embassy_extras::unborrow;
 use embedded_hal::blocking::delay::DelayUs;
@@ -123,7 +122,7 @@ pub struct Adc<'d, T: Instance> {
 }
 
 impl<'d, T: Instance> Adc<'d, T> {
-    pub fn new(_peri: impl Unborrow<Target = T> + 'd, mut delay: Delay) -> (Self, Delay) {
+    pub fn new(_peri: impl Unborrow<Target = T> + 'd, delay: &mut impl DelayUs<u32>) -> Self {
         unborrow!(_peri);
         unsafe {
             T::regs().cr().modify(|reg| {
@@ -142,18 +141,15 @@ impl<'d, T: Instance> Adc<'d, T> {
 
         delay.delay_us(1);
 
-        (
-            Self {
-                sample_time: Default::default(),
-                resolution: Resolution::default(),
-                calibrated_vdda: VDDA_CALIB_MV,
-                phantom: PhantomData,
-            },
-            delay,
-        )
+        Self {
+            sample_time: Default::default(),
+            resolution: Resolution::default(),
+            calibrated_vdda: VDDA_CALIB_MV,
+            phantom: PhantomData,
+        }
     }
 
-    pub fn enable_vref(&self, mut delay: Delay) -> (Vref, Delay) {
+    pub fn enable_vref(&self, delay: &mut impl DelayUs<u32>) -> Vref {
         unsafe {
             T::common_regs().ccr().modify(|reg| {
                 reg.set_vrefen(true);
@@ -166,7 +162,7 @@ impl<'d, T: Instance> Adc<'d, T> {
         //cortex_m::asm::delay(20_000_000);
         delay.delay_us(15);
 
-        (Vref {}, delay)
+        Vref {}
     }
 
     pub fn enable_temperature(&self) -> Temperature {
diff --git a/examples/stm32l4/src/bin/adc.rs b/examples/stm32l4/src/bin/adc.rs
index a909e1bb..a3c44d3c 100644
--- a/examples/stm32l4/src/bin/adc.rs
+++ b/examples/stm32l4/src/bin/adc.rs
@@ -16,8 +16,8 @@ use cortex_m_rt::entry;
 use cortex_m::delay::Delay;
 use embassy_stm32::adc::{Adc, Resolution};
 use stm32l4::stm32l4x5 as pac;
-use stm32l4xx_hal::rcc::PllSource;
 use stm32l4xx_hal::prelude::*;
+use stm32l4xx_hal::rcc::PllSource;
 
 #[entry]
 fn main() -> ! {
@@ -29,12 +29,11 @@ fn main() -> ! {
     let mut rcc = pp.RCC.constrain();
     let mut pwr = pp.PWR.constrain(&mut rcc.apb1r1);
 
-    let delay = Delay::new(cp.SYST, 80_000_000);
+    let mut delay = Delay::new(cp.SYST, 80_000_000);
 
     // TRY the other clock configuration
     // let clocks = rcc.cfgr.freeze(&mut flash.acr);
-    rcc
-        .cfgr
+    rcc.cfgr
         .sysclk(80.mhz())
         .pclk1(80.mhz())
         .pclk2(80.mhz())
@@ -69,7 +68,7 @@ fn main() -> ! {
 
     let p = embassy_stm32::init(Default::default());
 
-    let (mut adc, _) = Adc::new(p.ADC1, delay);
+    let mut adc = Adc::new(p.ADC1, &mut delay);
     //adc.enable_vref();
     adc.set_resolution(Resolution::EightBit);
     let mut channel = p.PC0;