stmhal: Put an array in ROM.

stmhal/usb.c

@@ -36,7 +36,7 @@ void pyb_usb_dev_init(int usb_dev_type) {
                 // so the memory is invalid after a soft reset (which resets the GC).
                 USBD_Init(&hUSBDDevice, &VCP_Desc, 0);
                 USBD_RegisterClass(&hUSBDDevice, &USBD_CDC);
-                USBD_CDC_RegisterInterface(&hUSBDDevice, &USBD_CDC_fops);
+                USBD_CDC_RegisterInterface(&hUSBDDevice, (USBD_CDC_ItfTypeDef*)&USBD_CDC_fops);
                 USBD_Start(&hUSBDDevice);
                 //USBD_Init(&USB_OTG_Core, USB_OTG_FS_CORE_ID, &USR_desc, &USBD_PYB_cb, &USR_cb);
                 break;

stmhal/usbd_cdc_interface.c

@@ -76,8 +76,7 @@ static void Error_Handler(void);
 //static void ComPort_Config(void);
 static void TIM_Config(void);
 
-USBD_CDC_ItfTypeDef USBD_CDC_fops = 
-{
+const USBD_CDC_ItfTypeDef USBD_CDC_fops = {
     CDC_Itf_Init,
     CDC_Itf_DeInit,
     CDC_Itf_Control,

stmhal/usbd_cdc_interface.h

@@ -47,7 +47,7 @@
    The period depends on USBD_CDC_POLLING_INTERVAL */
 #define USBD_CDC_POLLING_INTERVAL             10 /* in ms. The max is 65 and the min is 1 */
 
-extern USBD_CDC_ItfTypeDef USBD_CDC_fops;
+extern const USBD_CDC_ItfTypeDef USBD_CDC_fops;
 
 void USBD_CDC_SetInterrupt(int chr, void *data);
 void USBD_CDC_Tx(const char *str, uint32_t len);