qmk_firmware/platforms/avr/bootloaders/caterina.c

/* Copyright 2021 QMK
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "bootloader.h"

#include <avr/wdt.h>

__attribute__((weak))
void bootloader_jump(void) {
    // this block may be optional
    // TODO: figure it out

    uint16_t *const bootKeyPtr = (uint16_t *)0x0800;

    // Value used by Caterina bootloader use to determine whether to run the
    // sketch or the bootloader programmer.
    uint16_t bootKey = 0x7777;

    *bootKeyPtr = bootKey;

    // setup watchdog timeout
    wdt_enable(WDTO_60MS);

    // wait for watchdog timer to trigger
    while (1) { }
}