add simplest blink for STM32F407

F4:F401/blink/blink.c

@@ -0,0 +1,49 @@
+/*
+ * systick_blink.c
+ *
+ * Copyright 2017 Edward V. Emelianoff <eddy@sao.ru, edward.emelianoff@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301, USA.
+ */
+
+#include <stm32f4.h>
+
+static volatile uint32_t blink_ctr = 0;
+
+void sys_tick_handler(void){
+    ++blink_ctr;
+}
+
+TRUE_INLINE void gpio_setup(void){
+    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOEEN | RCC_AHB1ENR_GPIOCEN;
+    GPIOC->MODER = GPIO_MODER_MODER13_O;
+    GPIOE->MODER = GPIO_MODER_MODER2_O;
+}
+
+int main(void){
+    if(!StartHSE()) StartHSI();
+    // system frequency is 144MHz
+    SysTick_Config((uint32_t)144000); // 1ms
+    gpio_setup();
+    uint32_t ctr = blink_ctr;
+    while(1){
+        if(blink_ctr - ctr > 499){
+            ctr = blink_ctr;
+            pin_toggle(GPIOE, 1<<2);
+            pin_toggle(GPIOC, 1<<13);
+        }
+    }
+}