/** @file stk.c
 * Module handling the system timer (systick or STK for short)
 *
 * The module provides functions to configure and use the system timer embedded
 * in the cortex m core
 */

//--includes--------------------------------------------------------------------

#include "stk.h"
#include "stk_regs.h"

#include "rcc.h"


//--local definitions-----------------------------------------------------------

static volatile struct STK* regs = (struct STK*)STK_BASE_ADDRESS;

//--local variables-------------------------------------------------------------

static StkCallback callback;


//--public functions------------------------------------------------------------

uint32_t stk_configure(uint32_t period_us, StkCallback cb)
{
	stk_reset();

	struct RccClocks clocks;
	rcc_get_clocks(&clocks);

	uint32_t reload = period_us * (clocks.ahb_freq / 1000000 / 8);
	if (reload < 1) {
		//period is too small, try using the non-prescaled clock
		reload = period_us * (clocks.ahb_freq / 1000000);
		if (reload < 1) {
			//period is still too small
			return 1;
		}
		reg_set(regs->CTRL, STK_CTRL_CLKSOURCE);
	}
	reg_write(regs->LOAD, STK_LOAD_RELOAD, reload);
	reg_set(regs->CTRL, STK_CTRL_TICKINT);

	callback = cb;

	return 0;
}

void stk_reset(void)
{
	reg_reset(regs->CTRL, STK_CTRL_ENABLE);
	reg_reset(regs->CTRL, STK_CTRL_TICKINT);
	reg_reset(regs->CTRL, STK_CTRL_CLKSOURCE);
	reg_reset(regs->CTRL, STK_CTRL_COUNTFLAG);

	reg_write(regs->LOAD, STK_LOAD_RELOAD, 0);
	reg_write(regs->VAL, STK_VAL_CURRENT, 0);
}

void stk_start(void)
{
	reg_set(regs->CTRL, STK_CTRL_ENABLE);
}

void stk_stop(void)
{
	reg_reset(regs->CTRL, STK_CTRL_ENABLE);
}

uint32_t stk_read(void)
{
	return regs->VAL.word & 0x00FFFFFF;
}


//--local functions-------------------------------------------------------------

void hdr_sys_tick(void)
{
	callback();
}