/* Enable xosc (external xtal oscillator) */
samd21_sysctrl.xosc = ((SAMD21_SYSCTRL_XOSC_STARTUP_8192 << SAMD21_SYSCTRL_XOSC_STARTUP) |
(0 << SAMD21_SYSCTRL_XOSC_AMPGC) |
/* Enable xosc (external xtal oscillator) */
samd21_sysctrl.xosc = ((SAMD21_SYSCTRL_XOSC_STARTUP_8192 << SAMD21_SYSCTRL_XOSC_STARTUP) |
(0 << SAMD21_SYSCTRL_XOSC_AMPGC) |