sync_period       114 core/usb_sync.c         int sync_period = std_period * 2 + cur_cnt;                  // schedule the end of extended period at t = t(synch pulse) + sync_time
sync_period       118 core/usb_sync.c             sync_period -= (std_period - cur_cnt);
sync_period       122 core/usb_sync.c         *(volatile int*)(GPIO_VSYNC_MAX) = sync_period; // write the length of the extended period to the register