add some more files.

src/usb_lld.c

@@ -0,0 +1,26 @@
+#include "ch.h"
+#include "hal.h"
+#include "usb_lld.h"
+
+extern void USB_Istr (void);
+
+CH_IRQ_HANDLER (Vector90) {
+  CH_IRQ_PROLOGUE();
+
+  USB_Istr();
+
+  CH_IRQ_EPILOGUE();
+}
+
+void usb_lld_init (void) {
+  RCC->APB1ENR |= RCC_APB1ENR_USBEN;
+  NVICEnableVector (USB_LP_CAN1_RX0_IRQn,
+		    CORTEX_PRIORITY_MASK (STM32_USB_IRQ_PRIORITY));
+  /*
+   * Note that we also have other IRQs:
+   * 	USB_HP_CAN1_TX_IRQn
+   * 	USBWakeUp_IRQn
+   */
+  RCC->APB1RSTR = RCC_APB1RSTR_USBRST;
+  RCC->APB1RSTR = 0;
+}