From a61498aa6328e0305d6653045c0eecd0789e494d Mon Sep 17 00:00:00 2001
From: olikraus <olikraus@gmail.com>
Date: Wed, 5 Apr 2017 06:04:25 +0200
Subject: [PATCH] systick blink

---
 sys/arm/stm32l031x6/blink/main.c | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/sys/arm/stm32l031x6/blink/main.c b/sys/arm/stm32l031x6/blink/main.c
index 8416c529..7d6b4261 100644
--- a/sys/arm/stm32l031x6/blink/main.c
+++ b/sys/arm/stm32l031x6/blink/main.c
@@ -1,21 +1,46 @@
+// stm32flash -e 255 -w blink.hex -v /dev/ttyUSB0
+
 
 #include "stm32l031xx.h"
 
+volatile unsigned long SysTickCount = 0;
+
+void __attribute__ ((interrupt, used)) SysTick_Handler(void)
+{
+  SysTickCount++;
+  
+  if ( SysTickCount & 1 )
+    GPIOA->BSRR = GPIO_BSRR_BS_13;		/* atomic set PA13 */
+  else
+    GPIOA->BSRR = GPIO_BSRR_BR_13;		/* atomic clr PA13 */
+
+}
+
+
+
 int main()
 {
+
   //RCC->CFGR &= 
   RCC->IOPENR |= RCC_IOPENR_IOPAEN;		/* Enable clock for GPIO Port A */
   __NOP();
-  RCC->IOPRSTR |= RCC_IOPRSTR_IOPARST;	/* reset GPIO Port A */
   __NOP();
+
+  
   
   GPIOA->MODER &= ~GPIO_MODER_MODE13;	/* clear mode for PA13 */
-  GPIOA->MODER |= GPIO_MODER_MODE13_1;	/* Output mode for PA13 */
+  GPIOA->MODER |= GPIO_MODER_MODE13_0;	/* Output mode for PA13 */
   GPIOA->OTYPER &= ~GPIO_OTYPER_OT_13;	/* no Push/Pull for PA13 */
   GPIOA->OSPEEDR &= ~GPIO_OSPEEDER_OSPEED13;	/* low speed for PA13 */
   GPIOA->PUPDR &= ~GPIO_PUPDR_PUPD13;	/* no pullup/pulldown for PA13 */
   //GPIOA->BSRR = GPIO_BSRR_BS_13;		/* atomic set PA13 */
   GPIOA->BSRR = GPIO_BSRR_BR_13;		/* atomic clr PA13 */
+
+  //SysTick->LOAD = (SystemCoreClock/1000UL*(unsigned long)SYS_TICK_PERIOD_IN_MS) - 1;
+  SysTick->LOAD = 2000*500 - 1;
+  SysTick->VAL = 0;
+  SysTick->CTRL = 7;   /* enable, generate interrupt (SysTick_Handler), do not divide by 2 */
+  
   
   for(;;)
     ;