ao_gpio_set_mode(&AO_BOOT_APPLICATION_GPIO, AO_BOOT_APPLICATION_PIN, 0);
ao_disable_port(&AO_BOOT_APPLICATION_GPIO);
stm_rcc.apb1enr &= ~(1 << STM_RCC_APB1ENR_PWREN);
ao_gpio_set_mode(&AO_BOOT_APPLICATION_GPIO, AO_BOOT_APPLICATION_PIN, 0);
ao_disable_port(&AO_BOOT_APPLICATION_GPIO);
stm_rcc.apb1enr &= ~(1 << STM_RCC_APB1ENR_PWREN);