vbat.c

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#include "avr_compiler.h"
#include "vbat.h"

void vbat_reset(void)
{
        // Enable R/W access to the battery backup module.
        VBAT.CTRL = VBAT_ACCEN_bm;

        // Reset the module. (Reset bit is protected by CCP.)
        ENTER_CRITICAL_REGION();
        CCP = 0xD8;
        VBAT.CTRL = VBAT_RESET_bm;
        LEAVE_CRITICAL_REGION();
}

void vbat_enable_xosc(bool use1khz)
{
        // Enable the failure detection.
        VBAT.CTRL |= VBAT_XOSCFDEN_bm;

        /* A delay is needed to give the voltage in the backup system some time
         * to stabilise.
         */
        delay_us(200);

        // Enable oscillator, with 1 kHz or 1 Hz output.
        if (use1khz)
                VBAT.CTRL |= VBAT_XOSCEN_bm | VBAT_XOSCSEL_bm;
        else
                VBAT.CTRL |= VBAT_XOSCEN_bm;
}

uint8_t vbat_system_check(bool first_time_startup)
{
        uint8_t vbat_status;
        /*
         * Check if sufficient power was detected on the VBAT input. The brown-
         * out detector (BBBOD) will be sampled once when the device starts up
         * and the result is visible as the BBPWR flag.
         */
        if (VBAT.STATUS & VBAT_BBPWR_bm)
                vbat_status = VBAT_STATUS_NO_POWER;
        else {
                /*
                 * We hav sufficient power, now we check if a power-on-reset
                 * (BBPOR) was detected on VBAT. This is visible from the BBPORF
                 * flag which is also only updated once when the device starts.
                 */
                if (VBAT.STATUS & VBAT_BBPORF_bm) {
                        if (first_time_startup)
                                vbat_status = VBAT_STATUS_INIT;
                        else
                                vbat_status = VBAT_STATUS_BBPOR;
                }
                else if (VBAT.STATUS & VBAT_BBBORF_bm)
                        vbat_status = VBAT_STATUS_BBBOD;
                else {
                        VBAT.CTRL = VBAT_ACCEN_bm;
                        if (VBAT.STATUS & VBAT_XOSCFAIL_bm)
                                vbat_status = VBAT_STATUS_XOSCFAIL;
                        else
                                vbat_status = VBAT_STATUS_OK;
                }
        }
        return vbat_status;
}