Board mapping abstraction.

Makefile

@@ -26,7 +26,8 @@ PROJECT = f030f4
 #SRCS = blink.c
 #SRCS = ledtick.c
 #SRCS = cstartup.c
-SRCS = startup.c init.c success.c
+#SRCS = startup.c init.c success.c
+SRCS = startup.c board.c success.c
 OBJS = $(SRCS:.c=.o)
 CPU = -mthumb -mcpu=cortex-m0
 CFLAGS = $(CPU) -g -Wall -Wextra -Os

board.c

@@ -0,0 +1,56 @@
+/* board.c -- board mapping abstraction
+** Copyright (c) 2020 Renaud Fivet
+*/
+
+#define SYSTICK             ((volatile long *) 0xE000E010)
+#define SYSTICK_CSR         SYSTICK[ 0]
+#define SYSTICK_RVR         SYSTICK[ 1]
+#define SYSTICK_CVR         SYSTICK[ 2]
+
+#define CAT( a, b) a##b
+#define HEXA( a) CAT( 0x, a)
+#define RCC                 ((volatile long *) 0x40021000)
+#define RCC_AHBENR          RCC[ 5]
+#define RCC_AHBENR_IOP( h)  (1 << (17 + HEXA( h) - 0xA))
+
+#define GPIOA               ((volatile long *) 0x48000000)
+#define GPIOB               ((volatile long *) 0x48000400)
+#define GPIO( x) CAT( GPIO, x)
+#define MODER   0
+#define ODR     5
+
+/* user LED ON when PA4 is high */
+#define LED_IOP A
+#define LED_PIN 4
+#define LED_ON  1
+
+void SysTick_Handler( void) {
+#ifdef LED_ON
+    GPIO( LED_IOP)[ ODR] ^= 1 << LED_PIN ;   /* Toggle User LED */
+#endif
+}
+
+int init( void) {
+/* By default SYSCLK == HSI [8MHZ] */
+
+/* SYSTICK */
+    SYSTICK_RVR = 1000000 - 1 ;     /* HBA / 8 */
+    SYSTICK_CVR = 0 ;
+    SYSTICK_CSR = 3 ;               /* HBA / 8, Interrupt ON, Enable */
+    /* SysTick_Handler will execute every 1s from now on */
+
+#ifdef LED_ON
+/* User LED ON */
+    RCC_AHBENR |= RCC_AHBENR_IOP( LED_IOP) ;        /* Enable IOPx periph */
+    GPIO( LED_IOP)[ MODER] |= 1 << (LED_PIN * 2) ;  /* LED_IO Output [01],
+                                                    ** over default 00 */
+    /* OTYPER Push-Pull by default */
+    /* Pxn output default LOW at reset */
+# if LED_ON
+    SysTick_Handler() ;
+# endif
+#endif
+    return 0 ;
+}
+
+/* end of board.c */