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-rw-r--r--examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README21
-rw-r--r--examples/lm4f/stellaris-ek-lm4f120xl/miniblink/miniblink.c119
2 files changed, 136 insertions, 4 deletions
diff --git a/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README b/examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README
index f6441be..a19550d 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 e88413f..d03be0c 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;
+ }
+}