systick.c File Reference

SysTick timer configuration and millisecond utilities. More...

#include "uart.h"
#include "systick.h"
#include "controller.h"
#include <stdio.h>
#include <stdint.h>
#include "stm32f446xx.h"

Macros
#define	SYSTICK_LOAD_VAL   16000
#define	CTRL_ENABLE   (1U<<0)
#define	CTRL_CLKSRC   (1U<<2)
#define	CTRL_COUNTFLAG   (1U<<16)

Functions
void	SysTick_Handler (void)
	SysTick interrupt handler called every 1 millisecond.
void	systick_init (void)
	Initialize the SysTick timer for 1ms tick interrupts.
uint32_t	systickGetMillis (void)
	Get the current system uptime in milliseconds.
void	systickDelayMs (int delay)
	Busy-wait delay for a specified number of milliseconds.

Variables
volatile uint32_t	systickMillis = 0

Detailed Description

SysTick timer configuration and millisecond utilities.

This module configures the Cortex-M4 SysTick timer to generate a 1 ms tick interrupt. It maintains a global millisecond counter ('systickMillis`) and provides functions with time retrieval and busy-wait delays.

Macro Definition Documentation

CTRL_CLKSRC

#define CTRL_CLKSRC   (1U<<2)

CTRL_COUNTFLAG

#define CTRL_COUNTFLAG   (1U<<16)

CTRL_ENABLE

#define CTRL_ENABLE   (1U<<0)

SYSTICK_LOAD_VAL

#define SYSTICK_LOAD_VAL   16000

Function Documentation

SysTick_Handler()

void SysTick_Handler

(

void

)

SysTick interrupt handler called every 1 millisecond.

Increments the global milliseocnd counter and calls application-specific timeout functions:

• checkGreenLightTimeout() to release green light after timeout
• SysTick_CheckFirstPressTimeout() to handle first button press delay

Note

This interrupt handler is invoked by the Cortex-M4 SysTick hardware every millisecond (or configured tick period)

systick_init()

void systick_init

(

void

)

Initialize the SysTick timer for 1ms tick interrupts.

Configures the SysTick LOAD register and control register to generate interrupts every millisecond based on the system clock.

systickDelayMs()

void systickDelayMs

(

int

delay

)

Busy-wait delay for a specified number of milliseconds.

Uses systickGetMillis() to implement a simple blocking delay.

Parameters

delay

Number of milliseconds to wait

Note

This is a blocking function and will halt CPU execution. Do not use in time-critical or interrupt-sensitive code.

systickGetMillis()

uint32_t systickGetMillis

(

void

)

Get the current system uptime in milliseconds.

Returns the number of milliseconds elapsed since SysTick initialization.

Returns

Current millisecond count

Variable Documentation

systickMillis

volatile uint32_t systickMillis = 0