USB_OTG_GlobalTypeDef *USBx = USB_OTG_FS;

#define USBx_HOST       ((USB_OTG_HostTypeDef *)((uint32_t)USBx + USB_OTG_HOST_BASE))
#define USBx_DEVICE     ((USB_OTG_DeviceTypeDef *)((uint32_t)USBx + USB_OTG_DEVICE_BASE))
#define USBx_INEP(i)    ((USB_OTG_INEndpointTypeDef *)((uint32_t)USBx + USB_OTG_IN_ENDPOINT_BASE + ((i) * USB_OTG_EP_REG_SIZE)))
#define USBx_OUTEP(i)   ((USB_OTG_OUTEndpointTypeDef *)((uint32_t)USBx + USB_OTG_OUT_ENDPOINT_BASE + ((i) * USB_OTG_EP_REG_SIZE)))
#define USBx_DFIFO(i)   *(__IO uint32_t *)((uint32_t)USBx + USB_OTG_FIFO_BASE + ((i) * USB_OTG_FIFO_SIZE))
#define USBx_PCGCCTL    *(__IO uint32_t *)((uint32_t)USBx + USB_OTG_PCGCCTL_BASE)

#define USBD_FS_TRDT_VALUE 5UL
#define USB_OTG_SPEED_FULL 3


void usb_irqhandler(void);

void OTG_FS_IRQ_Handler(void) {
  NVIC_DisableIRQ(OTG_FS_IRQn);
  //__disable_irq();
  usb_irqhandler();
  //__enable_irq();
  NVIC_EnableIRQ(OTG_FS_IRQn);
}

void usb_init(void) {
  REGISTER_INTERRUPT(OTG_FS_IRQn, OTG_FS_IRQ_Handler, 1500000U, FAULT_INTERRUPT_RATE_USB) //TODO: Find out a better rate limit for USB. Now it's the 1.5MB/s rate

  // full speed PHY, do reset and remove power down
  /*puth(USBx->GRSTCTL);
  print(" resetting PHY\n");*/
  while ((USBx->GRSTCTL & USB_OTG_GRSTCTL_AHBIDL) == 0);
  //print("AHB idle\n");

  // reset PHY here
  USBx->GRSTCTL |= USB_OTG_GRSTCTL_CSRST;
  while ((USBx->GRSTCTL & USB_OTG_GRSTCTL_CSRST) == USB_OTG_GRSTCTL_CSRST);
  //print("reset done\n");

  // internal PHY, force device mode
  USBx->GUSBCFG = USB_OTG_GUSBCFG_PHYSEL | USB_OTG_GUSBCFG_FDMOD;

  // slowest timings
  USBx->GUSBCFG |= ((USBD_FS_TRDT_VALUE << 10) & USB_OTG_GUSBCFG_TRDT);

  // power up the PHY
#ifdef STM32F4
  USBx->GCCFG = USB_OTG_GCCFG_PWRDWN;

  //USBx->GCCFG |= USB_OTG_GCCFG_VBDEN | USB_OTG_GCCFG_SDEN |USB_OTG_GCCFG_PDEN | USB_OTG_GCCFG_DCDEN;

  /* B-peripheral session valid override enable*/
  USBx->GOTGCTL |= USB_OTG_GOTGCTL_BVALOVAL;
  USBx->GOTGCTL |= USB_OTG_GOTGCTL_BVALOEN;
#else
  USBx->GCCFG = USB_OTG_GCCFG_PWRDWN | USB_OTG_GCCFG_NOVBUSSENS;
#endif

  // be a device, slowest timings
  //USBx->GUSBCFG = USB_OTG_GUSBCFG_FDMOD | USB_OTG_GUSBCFG_PHYSEL | USB_OTG_GUSBCFG_TRDT | USB_OTG_GUSBCFG_TOCAL;
  //USBx->GUSBCFG |= (uint32_t)((USBD_FS_TRDT_VALUE << 10) & USB_OTG_GUSBCFG_TRDT);
  //USBx->GUSBCFG = USB_OTG_GUSBCFG_PHYSEL | USB_OTG_GUSBCFG_TRDT | USB_OTG_GUSBCFG_TOCAL;

  // **** for debugging, doesn't seem to work ****
  //USBx->GUSBCFG |= USB_OTG_GUSBCFG_CTXPKT;

  // reset PHY clock
  USBx_PCGCCTL = 0;

  // enable the fancy OTG things
  // DCFG_FRAME_INTERVAL_80 is 0
  //USBx->GUSBCFG |= USB_OTG_GUSBCFG_HNPCAP | USB_OTG_GUSBCFG_SRPCAP;
  USBx_DEVICE->DCFG |= USB_OTG_SPEED_FULL | USB_OTG_DCFG_NZLSOHSK;

  //USBx_DEVICE->DCFG = USB_OTG_DCFG_NZLSOHSK | USB_OTG_DCFG_DSPD;
  //USBx_DEVICE->DCFG = USB_OTG_DCFG_DSPD;

  // clear pending interrupts
  USBx->GINTSTS = 0xBFFFFFFFU;

  // setup USB interrupts
  // all interrupts except TXFIFO EMPTY
  //USBx->GINTMSK = 0xFFFFFFFF & ~(USB_OTG_GINTMSK_NPTXFEM | USB_OTG_GINTMSK_PTXFEM | USB_OTG_GINTSTS_SOF | USB_OTG_GINTSTS_EOPF);
  //USBx->GINTMSK = 0xFFFFFFFF & ~(USB_OTG_GINTMSK_NPTXFEM | USB_OTG_GINTMSK_PTXFEM);
  USBx->GINTMSK = USB_OTG_GINTMSK_USBRST | USB_OTG_GINTMSK_ENUMDNEM | USB_OTG_GINTMSK_OTGINT |
                  USB_OTG_GINTMSK_RXFLVLM | USB_OTG_GINTMSK_GONAKEFFM | USB_OTG_GINTMSK_GINAKEFFM |
                  USB_OTG_GINTMSK_OEPINT | USB_OTG_GINTMSK_IEPINT | USB_OTG_GINTMSK_USBSUSPM |
                  USB_OTG_GINTMSK_CIDSCHGM | USB_OTG_GINTMSK_SRQIM | USB_OTG_GINTMSK_MMISM | USB_OTG_GINTMSK_EOPFM;

  USBx->GAHBCFG = USB_OTG_GAHBCFG_GINT;

  // DCTL startup value is 2 on new chip, 0 on old chip
  USBx_DEVICE->DCTL = 0;

  // enable the IRQ
  NVIC_EnableIRQ(OTG_FS_IRQn);
}