Enable nvic and exti support for L1

And include an example that uses it.

examples/stm32/l1/stm32l-discovery/button-irq-printf/Makefile

@@ -0,0 +1,24 @@
+##
+## This file is part of the libopencm3 project.
+##
+## Copyright (C) 2009 Uwe Hermann <uwe@hermann-uwe.de>
+##
+## This library is free software: you can redistribute it and/or modify
+## it under the terms of the GNU Lesser General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This library is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU Lesser General Public License for more details.
+##
+## You should have received a copy of the GNU Lesser General Public License
+## along with this library.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+BINARY = main
+LDSCRIPT = ../../../../../lib/stm32/l1/stm32l15xxb.ld
+
+include ../../Makefile.include
+

examples/stm32/l1/stm32l-discovery/button-irq-printf/README

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+* Counts how long the user button was held down (in ms)
+* Uses one free running counter plus EXTI as an ugly input capture
+115200@8n1 console on PA2 (tx only)
+

examples/stm32/l1/stm32l-discovery/button-irq-printf/main.c

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+/*
+ * Karl Palsson, 2012 <karlp@tweak.net.au
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <libopencm3/cm3/nvic.h>
+#include <libopencm3/stm32/l1/rcc.h>
+#include <libopencm3/stm32/l1/gpio.h>
+#include <libopencm3/stm32/exti.h>
+#include <libopencm3/stm32/usart.h>
+
+#include "syscfg.h"
+
+static struct state_t state;
+
+void clock_setup(void) {
+    /* Lots of things on all ports... */
+    rcc_peripheral_enable_clock(&RCC_AHBENR, RCC_AHBENR_GPIOAEN);
+    rcc_peripheral_enable_clock(&RCC_AHBENR, RCC_AHBENR_GPIOBEN);
+
+    /* Enable clocks for USART2. */
+    rcc_peripheral_enable_clock(&RCC_APB1ENR, RCC_APB1ENR_USART2EN);
+}
+
+void gpio_setup(void) {
+    gpio_mode_setup(LED_DISCO_GREEN_PORT, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, LED_DISCO_GREEN_PIN);
+
+    /* Setup GPIO pins for USART2 transmit. */
+    gpio_mode_setup(GPIOA, GPIO_MODE_AF, GPIO_PUPD_NONE, GPIO2);
+
+    /* Setup USART2 TX pin as alternate function. */
+    gpio_set_af(GPIOA, GPIO_AF7, GPIO2);
+}
+
+void usart_setup(void) {
+    usart_set_baudrate(USART_CONSOLE, 115200);
+    usart_set_databits(USART_CONSOLE, 8);
+    usart_set_stopbits(USART_CONSOLE, USART_STOPBITS_1);
+    usart_set_mode(USART_CONSOLE, USART_MODE_TX);
+    usart_set_parity(USART_CONSOLE, USART_PARITY_NONE);
+    usart_set_flow_control(USART_CONSOLE, USART_FLOWCONTROL_NONE);
+
+    /* Finally enable the USART. */
+    usart_enable(USART_CONSOLE);
+}
+
+/**
+ * Use USART_CONSOLE as a console.
+ * @param file
+ * @param ptr
+ * @param len
+ * @return
+ */
+int _write(int file, char *ptr, int len) {
+    int i;
+
+    if (file == STDOUT_FILENO || file == STDERR_FILENO) {
+        for (i = 0; i < len; i++) {
+            if (ptr[i] == '\n') {
+                usart_send_blocking(USART_CONSOLE, '\r');
+            }
+            usart_send_blocking(USART_CONSOLE, ptr[i]);
+        }
+        return i;
+    }
+    errno = EIO;
+    return -1;
+}
+
+void BUTTON_DISCO_USER_isr(void) {
+    exti_reset_request(BUTTON_DISCO_USER_EXTI);
+    if (state.falling) {
+        state.falling = false;
+        exti_set_trigger(BUTTON_DISCO_USER_EXTI, EXTI_TRIGGER_RISING);
+        //        ILOG("fell: %d\n", TIM_CNT(TIM7));
+        puts("fell!\n");
+    } else {
+        puts("Rose!\n");
+        //        TIM_CNT(TIM7) = 0;
+        state.falling = true;
+        exti_set_trigger(BUTTON_DISCO_USER_EXTI, EXTI_TRIGGER_FALLING);
+    }
+}
+
+void setup_buttons(void) {
+    /* Enable EXTI0 interrupt. */
+    nvic_enable_irq(BUTTON_DISCO_USER_NVIC);
+
+    gpio_mode_setup(BUTTON_DISCO_USER_PORT, GPIO_MODE_INPUT, GPIO_PUPD_NONE, BUTTON_DISCO_USER_PIN);
+
+    /* Configure the EXTI subsystem. */
+    exti_select_source(BUTTON_DISCO_USER_EXTI, BUTTON_DISCO_USER_PORT);
+    state.falling = false;
+    exti_set_trigger(BUTTON_DISCO_USER_EXTI, EXTI_TRIGGER_RISING);
+    exti_enable_request(BUTTON_DISCO_USER_EXTI);
+}
+
+int main(void) {
+    int i;
+    int j = 0;
+    clock_setup();
+    gpio_setup();
+    usart_setup();
+    puts("hi guys!\n");
+    setup_buttons();
+    while (1) {
+        puts("tick:");
+        putchar('a' + (j++ % 26));
+        gpio_toggle(GPIOB, GPIO7); /* LED on/off */
+        for (i = 0; i < 100000; i++) /* Wait a bit. */
+            __asm__("NOP");
+    }
+
+    return 0;
+}

examples/stm32/l1/stm32l-discovery/button-irq-printf/syscfg.h

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+/*
+ * General configuration of the device
+ *
+ * Karl Palsson <karlp@tweak.net.au> 2012
+ */
+
+#ifndef SYSCFG_H
+#define	SYSCFG_H
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+#include <libopencm3/stm32/l1/gpio.h>
+#include <libopencm3/stm32/nvic.h>
+#include <libopencm3/stm32/exti.h>
+#include <libopencm3/stm32/usart.h>
+
+
+#define USART_CONSOLE USART2
+#define USE_NASTYLOG 1
+
+#define LED_DISCO_GREEN_PORT GPIOB
+#define LED_DISCO_GREEN_PIN GPIO7
+#define LED_DISCO_BLUE_PORT GPIOB
+#define LED_DISCO_BLUE_PIN GPIO6
+
+#define BUTTON_DISCO_USER_PORT GPIOA
+#define BUTTON_DISCO_USER_PIN GPIO0
+#define BUTTON_DISCO_USER_EXTI EXTI0
+#define BUTTON_DISCO_USER_isr exti0_isr
+#define BUTTON_DISCO_USER_NVIC NVIC_EXTI0_IRQ
+
+
+    struct state_t {
+        bool falling;
+    };
+
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* SYSCFG_H */
+