Implement RTC module's basic functionnalities

FUnctions need a cleanup and some details need be ironned, like the
clock management since the whole backup domain must be reset to
configure them

drv/rtc.c

@@ -0,0 +1,139 @@
+//--includes--------------------------------------------------------------------
+
+#include "rtc.h"
+#include "rtc_regs.h"
+#include "rcc.h"
+#include "pwr.h"
+#include "nvic.h"
+
+
+//--local definitions-----------------------------------------------------------
+
+//--local variables-------------------------------------------------------------
+
+static volatile struct RTC* regs = (struct RTC*)RTC_BASE_ADDRESS;
+static RtcCallback rtc_callback;
+
+
+//--public functions------------------------------------------------------------
+
+void rtc_configure(uint32_t period_ms, enum RtcClockSrc clock_src,
+		enum RtcIrq irq_mask, uint32_t alarm_tick, RtcCallback callback)
+{
+	pwr_configure_bkp_write(true);
+	//start RTC
+	rcc_configure_rtc(true, clock_src + 1);
+
+	//rtc_reset();
+	rcc_enable(RCC_AHB_NONE, RCC_APB1_BKP, RCC_APB2_NONE);
+	//rcc_configure_rtc(false, RCC_RTC_CLOCK_SRC_NONE);
+
+	//compute prescaler
+	uint32_t prescaler = 0;
+	switch (clock_src) {
+		case RTC_CLOCK_SRC_LSE:
+			prescaler = 32768000; //32.768kHz
+			break;
+		case RTC_CLOCK_SRC_LSI:
+			prescaler = 40000000; //40khz
+			break;
+		case RTC_CLOCK_SRC_HSE:
+			prescaler = 62500000; //8Mhz / 128
+			break;
+		default:
+			return;
+	}
+	prescaler /= period_ms;
+
+	//wait for registers to synchronize
+	regs->CRL.RSF = 0;
+	while (regs->CRL.RSF != 1) {}
+	//wait for last operation to finish
+	while (regs->CRL.RTOFF != 1) {}
+
+	//enable core configuration
+	regs->CRL.CNF = 1;
+
+	//configure core registers
+	regs->PRLH.PRL = prescaler >> 16;
+	regs->PRLL.PRL = prescaler;
+	regs->ALRH.RTC_ALR = alarm_tick >> 16;
+	regs->ALRL.RTC_ALR = alarm_tick;
+
+	//apply irq config
+	regs->CRH.word |= irq_mask & 0x7;
+
+	//disable/apply core configuration
+	regs->CRL.CNF = 0;
+
+	//wait for last operation to finish
+	while (regs->CRL.RTOFF != 1) {}
+
+	pwr_configure_bkp_write(false);
+
+	if (callback) {
+		rtc_callback = callback;
+		nvic_enable(NVIC_IRQ_RTC);
+	}
+}
+
+void rtc_reset(void)
+{
+	nvic_disable(NVIC_IRQ_RTC);
+	pwr_configure_bkp_write(true);
+	rcc_enable(RCC_AHB_NONE, RCC_APB1_BKP, RCC_APB2_NONE);
+
+	//wait for registers to synchronize
+	regs->CRL.RSF = 0;
+	//while (regs->CRL.RSF != 1) {}
+	//wait for last operation to finish
+	while (regs->CRL.RTOFF != 1) {}
+
+	//clear config registers
+	regs->CRH.word &= ~0x7;
+	regs->CRL.word &= ~0xf;
+
+	//enable core configuration
+	regs->CRL.CNF = 1;
+
+	//reset core registers. DIV register can be ignore since it is reset on any
+	//changes of the other 2
+	regs->PRLH.PRL = 0x0;
+	regs->PRLL.PRL = 0x8000;
+	regs->CNTH.RTC_CNT = 0x0;
+	regs->CNTL.RTC_CNT = 0x0;
+
+	//disable/apply core configuration
+	regs->CRL.CNF = 0;
+
+	//wait for last operation to finish
+	while (regs->CRL.RTOFF != 1) {}
+
+	rcc_configure_rtc(false, RCC_RTC_CLOCK_SRC_NONE);
+	rcc_disable(RCC_AHB_NONE, RCC_APB1_BKP, RCC_APB2_NONE);
+	pwr_configure_bkp_write(false);
+}
+
+uint32_t stk_read_s(void)
+{
+	//wait for core registers to be synchronized, immediate most of the time
+	while (regs->CRL.RSF != 1) {}
+
+	uint32_t time = regs->CNTH.RTC_CNT << 16;
+	time |= regs->CNTL.RTC_CNT << 0;
+
+	return time;
+}
+
+
+//--local functions-------------------------------------------------------------
+
+void hdr_rtc(void)
+{
+	nvic_clear_pending(NVIC_IRQ_RTC);
+
+	//copy and clear and pass along src flags
+	enum RtcIrq src = regs->CRL.word & 0x7;
+	regs->CRL.word &= ~(0x7);
+	rtc_callback(src);
+}

drv/rtc.h

@@ -0,0 +1,43 @@
+/** @file rtc.h
+ * Module handling the Real-Time Clock (RTC).
+ *
+ */
+
+#ifndef _RTC_H_
+#define _RTC_H_
+
+//--includes--------------------------------------------------------------------
+
+#include "stdint.h"
+
+
+//--type definitions------------------------------------------------------------
+
+enum RtcClockSrc {
+	RTC_CLOCK_SRC_LSE  = 0x0,
+	RTC_CLOCK_SRC_LSI  = 0x1,
+	RTC_CLOCK_SRC_HSE  = 0x2,
+};
+
+enum RtcIrq {
+	RTC_IRQ_NONE     = 0,
+	RTC_IRQ_SECOND   = 0x1 << 0,
+	RTC_IRQ_ALARM    = 0x1 << 1,
+	RTC_IRQ_OVERFLOW = 0x1 << 2,
+};
+
+typedef void (*RtcCallback)(enum RtcIrq src);
+
+
+//--functions-------------------------------------------------------------------
+
+void rtc_configure(uint32_t period_ms, enum RtcClockSrc clock_src,
+		enum RtcIrq irq_mask, uint32_t alarm_tick, RtcCallback callback);
+
+void rtc_reset(void);
+
+uint32_t stk_read_s(void);
+
+
+#endif //_RTC_H_
+