#include "stm32l_rtc.h"
#include <hal.h>
#include <ch.h>
#include <stm32l1xx.h>

void set_rtc(const time_t *time)
{
    // Allow RTC write
    RTC->WPR = 0xCA;
    RTC->WPR = 0x53;
    
    // Enter RTC init mode
    RTC->ISR |= RTC_ISR_INIT;
    chThdSleepMilliseconds(10);
    
    // Program clock frequency (32.768kHz crystal)
    // Reference manual says to write the prescalers in two operations..
    RTC->PRER = 0x007F0000;
    RTC->PRER = 0x007F00FF;
    
    // Program the date and time
    RTC->DR = (
        ((1) << 20) | // Year tens
        ((3) << 16) | // Year units
        (time->day_of_week << 13) | // Day of week
        ((0) << 12) | // Month tens
        ((1) << 8) | // Month units
        ((0) << 4) | // Day tens
        ((1) << 0) // Day units
    );
    
    RTC->TR = (
        ((time->hour / 10) << 20) | // Hour tens
        ((time->hour % 10) << 16) | // Hour units
        ((time->minute / 10) << 12) | // Minute tens
        ((time->minute % 10) << 8) | // Minute units
        ((time->second / 10) << 4) | // Second tens
        ((time->second % 10) << 0) // Second units
    );
    
    // Start the RTC
    RTC->ISR &= ~RTC_ISR_INIT;
    
    chThdSleepMilliseconds(10); // Wait for RTC to start
}

bool get_rtc(time_t *time)
{
    if (!(RTC->ISR & RTC_ISR_INITS))
        return false;
    
    uint32_t tr = RTC->TR;
    uint32_t dr = RTC->DR; // Consistency guaranteed by hardware.
    
    time->day_of_week = (dr >> 13) & 0x7;
    
    time->hour   = ((tr >> 20) & 0x3) * 10 + ((tr >> 16) & 0xF);
    time->minute = ((tr >> 12) & 0x7) * 10 + ((tr >>  8) & 0xF);
    time->second = ((tr >>  4) & 0x7) * 10 + ((tr >>  0) & 0xF);
    
    return true;
}