diff --git a/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README b/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README
index f6441bec..a19550d6 100644
--- a/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README
+++ b/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README
@@ -2,8 +2,21 @@
 README
 ------------------------------------------------------------------------------
 
-Flashes the Red, Green and Blue diodes on the board, in order.
-RED controlled by PF1
-Green controlled by PF3
-Blue controlled by PF2
+This example demonstrates the following:
+ * Configuriong GPIO pins
+ * Toggling GPIO pins
+ * Setting up and using GPIO interrupts
+ * Unlocking protected GPIO pins
+ * Controlling the system clock
+ * Changing the system clock on the fly
+
+Flashes the Red, Green and Blue diodes on the board, in order. The system clock
+starts at 80MHz.
+Pressing SW2 toggles the system clock between 80MHz, 57MHz, 40MHz ,20MHz, and
+16MHz by changing the PLL divisor.
+Pressing SW1 bypasses the PLL completely, and runs off the raw 16MHz clock
+provided by the external crystal oscillator.
+The LEDs will toggle at different speeds, depending on the system clock. The
+system clock changes are handled within the interrupt service routine.
+
 
diff --git a/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/miniblink.c b/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/miniblink.c
index e88413fd..d03be0cc 100644
--- a/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/miniblink.c
+++ b/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/miniblink.c
@@ -27,8 +27,14 @@
  * Green controlled by PF3
  * Blue controlled by PF2
  */
+#include <libopencm3/cm3/nvic.h>
 #include <libopencm3/lm4f/systemcontrol.h>
+#include <libopencm3/lm4f/rcc.h>
 #include <libopencm3/lm4f/gpio.h>
+#include <libopencm3/lm4f/nvic.h>
+
+#include <stdbool.h>
+#include <stdio.h>
 
 /* This is how the RGB LED is connected on the stellaris launchpad */
 #define RGB_PORT	GPIOF
@@ -38,6 +44,44 @@ enum {
 	LED_B	= GPIO2,
 };
 
+/* This is how the user switches are connected to GPIOF */
+enum {
+	USR_SW1	= GPIO4,
+	USR_SW2	= GPIO0,
+};
+
+/* The divisors we loop through when the user presses SW2 */
+enum {
+	PLL_DIV_80MHZ 	= 5,
+	PLL_DIV_57MHZ 	= 7,
+	PLL_DIV_40MHZ 	= 10,
+	PLL_DIV_20MHZ 	= 20,
+	PLL_DIV_16MHZ 	= 25,
+};
+
+static const u8 plldiv[] = {
+	PLL_DIV_80MHZ,
+	PLL_DIV_57MHZ,
+	PLL_DIV_40MHZ,
+	PLL_DIV_20MHZ,
+	PLL_DIV_16MHZ,
+	0
+};
+/* The PLL divisor we are currently on */
+static size_t ipll = 0;
+/* Are we bypassing the PLL, or not? */
+static bool bypass = false;
+
+/*
+ * Clock setup:
+ * Take the main crystal oscillator at 16MHz, run it through the PLL, and divide
+ * the 400MHz PLL clock to get a system clock of 80MHz.
+ */
+static void clock_setup(void)
+{
+	rcc_sysclk_config(OSCSRC_MOSC, XTAL_16M, PLL_DIV_80MHZ);
+}
+
 /*
  * GPIO setup:
  * Enable the pins driving the RGB LED as outputs.
@@ -53,6 +97,46 @@ static void gpio_setup(void)
 
 	GPIO_DIR(RGB_PORT) |= outpins; /* Configure outputs. */
 	GPIO_DEN(RGB_PORT) |= outpins; /* Enable digital function on outputs. */
+
+	/*
+	 * Now take care of our buttons
+	 */
+	const u32 btnpins = USR_SW1 | USR_SW2;
+
+	/*
+	 * PF0 is locked by default. We need to unlock the GPIO_CR register,
+	 * then enable PF0 commit. After we do this, we can setup PF0. If we
+	 * don't do this, any configuration done to PF0 is lost, and we will not
+	 * have a PF0 interrupt.
+	 */
+	GPIO_LOCK(GPIOF) = 0x4C4F434B;
+	GPIO_CR(GPIOF) |= USR_SW2;
+
+	/* Configure pins as inputs. */
+	GPIO_DIR(GPIOF) &= ~btnpins;
+	/* Enable digital function on the pins. */
+	GPIO_DEN(GPIOF) |= btnpins;
+	/* Pull-up the pins. We don't have an external pull-up */
+	GPIO_PUR(GPIOF) |= btnpins;
+}
+
+/*
+ * IRQ setup:
+ * Trigger an interrupt whenever a button is depressed.
+ */
+static void irq_setup(void)
+{
+	const u32 btnpins = USR_SW1 | USR_SW2;
+	/* Configure interrupt as edge-sensitive */
+	GPIO_IS(GPIOF) &= ~btnpins;
+	/* Interrupt only respond to rising or falling edge (single-edge) */
+	GPIO_IBE(GPIOF) &= ~btnpins;
+	/* Trigger interrupt on rising-edge (when button is depressed) */
+	GPIO_IEV(GPIOF) |= btnpins;
+	/* Finally, Enable interrupt */
+	GPIO_IM(GPIOF) |= btnpins;
+	/* Enable the interrupt in the NVIC as well */
+	nvic_enable_irq(NVIC_GPIOF_IRQ);
 }
 
 #define FLASH_DELAY 800000
@@ -67,7 +151,9 @@ int main(void)
 {
 	int i;
 
+	clock_setup();
 	gpio_setup();
+	irq_setup();
 
 	/* Blink each color of the RGB LED in order. */
 	while (1) {
@@ -98,3 +184,36 @@ int main(void)
 
 	return 0;
 }
+
+void gpiof_isr(void)
+{
+	if (GPIO_RIS(GPIOF) & USR_SW1) {
+		/* SW1 was just depressed */
+		bypass = !bypass;
+		if (bypass) {
+			rcc_pll_bypass_enable();
+			/*
+			 * The divisor is still applied to the raw clock.
+			 * Disable the divisor, or we'll divide the raw clock.
+			 */
+			SYSCTL_RCC &= ~SYSCTL_RCC_USESYSDIV;
+		}
+		else
+		{
+			rcc_change_pll_divisor(plldiv[ipll]);
+		}
+		/* Clear interrupt source */
+		GPIO_ICR(GPIOF) = USR_SW1;
+	}
+
+	if (GPIO_RIS(GPIOF) & USR_SW2) {
+		/* SW2 was just depressed */
+		if (!bypass) {
+			if (plldiv[++ipll] == 0)
+				ipll = 0;
+			rcc_change_pll_divisor(plldiv[ipll]);
+		}
+		/* Clear interrupt source */
+		GPIO_ICR(GPIOF) = USR_SW2;
+	}
+}