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lm4f: Update miniblink example to demonstrate clock API

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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.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
This commit is contained in:
Alexandru Gagniuc 2013-01-09 02:12:21 -06:00
parent 4b2d9aca7b
commit 7ba100f569
2 changed files with 136 additions and 4 deletions
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21
examples/lm4f/stellaris-ek-lm4f120xl/miniblink/README
View File

@ -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.

119
examples/lm4f/stellaris-ek-lm4f120xl/miniblink/miniblink.c
View File

@ -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;
}
}