diff --git a/bluepill-rs/src/main.rs b/bluepill-rs/src/main.rs
index 8c1e870..b13fbb8 100644
--- a/bluepill-rs/src/main.rs
+++ b/bluepill-rs/src/main.rs
@@ -1,27 +1,16 @@
-//! Blinks an LED
-//!
-//! This assumes that a LED is connected to pc13 as is the case on the blue pill board.
-//!
-//! Note: Without additional hardware, PC13 should not be used to drive an LED, see page 5.1.2 of
-//! the reference manual for an explanation. This is not an issue on the blue pill.
-
-// #![deny(unsafe_code)]
+#![deny(unsafe_code)]
 #![no_std]
 #![no_main]
 
-// use cortex_m::singleton;
-use panic_halt as _;
-use stm32f1xx_hal::{dma, gpio, pac, prelude::*, rcc, serial, timer};
-use systick_monotonic::Systick;
-
 mod i2c_reg_slave;
 mod i2c_slave;
 
-// static mut BUFFER: Option<&mut [u8; 256]> = None;
-
 #[rtic::app(device = stm32f1::stm32f103, peripherals = true)]
 mod app {
-    use super::*;
+    use cortex_m::singleton;
+    use panic_halt as _;
+    use stm32f1xx_hal::{dma, gpio, pac, prelude::*, serial, timer};
+    use systick_monotonic::Systick;
 
     // A monotonic timer to enable scheduling in RTIC
     #[monotonic(binds = SysTick, default = true)]
@@ -32,9 +21,9 @@ mod app {
 
     #[local]
     struct Local {
-        tx: dma::TxDma<serial::Tx<pac::USART1>, dma::dma1::C4>,
+        tx: Option<dma::TxDma<serial::Tx<pac::USART1>, dma::dma1::C4>>,
         delay: timer::Delay<pac::TIM1, 1_000_000>,
-        led: gpio::Pin<'C', 13, gpio::Output>,
+        led: gpio::gpioc::PC13<gpio::Output>,
     }
 
     #[init]
@@ -46,20 +35,13 @@ mod app {
 
         // Freeze the configuration of all the clocks in the system and store the frozen frequencies in
         // `clocks`
-        let clocks = rcc.cfgr.freeze_with_config(
-            rcc::Config {
-                // HSE frequency
-                hse: Some(8_000_000),
-                // PLLMUL represented by an integer -2
-                pllmul: Some(9 - 2),
-                // PCLK1 freq must be 36 MHz or less
-                ppre1: stm32f1xx_hal::rcc::PPre::Div2,
-                // ADCCLK freq must be 14 MHz or less
-                adcpre: pac::rcc::cfgr::ADCPRE_A::Div6,
-                ..Default::default()
-            },
-            &mut flash.acr,
-        );
+        let clocks = rcc
+            .cfgr
+            // hf external quartz frequency
+            .use_hse(8.MHz())
+            // system clock frequency
+            .sysclk(72.MHz())
+            .freeze(&mut flash.acr);
 
         // Initialize the monotonic
         let mono = Systick::new(cx.core.SYST, clocks.sysclk().to_Hz());
@@ -71,7 +53,7 @@ mod app {
         let mut afio = cx.device.AFIO.constrain();
         let dma1 = cx.device.DMA1.split();
 
-        // USART1
+        // Serial config
         let tx = gpioa.pa9.into_alternate_push_pull(&mut gpioa.crh);
         let rx = gpioa.pa10; //.into_pull_up_input(&mut gpioa.crh);
 
@@ -86,14 +68,10 @@ mod app {
             &clocks,
         );
 
-        // unsafe {
-        //     BUFFER = Some(singleton!(: [u8; 256] = [0b01010101; 256]).unwrap());
-        // }
-
         (
             Shared {},
             Local {
-                tx: serial.tx.with_dma(dma1.4),
+                tx: Some(serial.tx.with_dma(dma1.4)),
 
                 // Configure timer
                 delay: cx.device.TIM1.delay_us(&clocks),
@@ -108,17 +86,19 @@ mod app {
 
     #[idle(local = [tx, delay, led])]
     fn idle(cx: idle::Context) -> ! {
-        // Wait for the timer to trigger an update and change the state of the LED
-        loop {
-            // let xfer = cx.shared.tx.lock(|tx| tx.write(BUFFER.unwrap()));
+        let mut buf = singleton!(: [u8; 256] = [0b01010101; 256]).unwrap();
+        let mut tx = cx.local.tx.take().unwrap();
 
-            cx.local.delay.delay(1u32.secs());
+        loop {
+            let xfer = tx.write(buf);
+
+            cx.local.delay.delay(1.secs());
             cx.local.led.set_high();
 
-            cx.local.delay.delay(1u32.secs());
+            cx.local.delay.delay(1.secs());
             cx.local.led.set_low();
 
-            // xfer.wait();
+            (buf, tx) = xfer.wait();
         }
     }
 }