atusb/fw/: flash a boot loader instead of the application (in progress)

- boot.c: basic boot loader that runs DFU for 2 s, then starts the payload
- board.h (DFU_USB_VENDOR, DFU_USB_PRODUCT): added USB IDs for DFU
- flash.c: stubs for board-specific Flash functions
- Makefile: build boot.hex for the boot loader
- Makefile (prog): load the boot loader at its rightful place
- Makefile (prog): also set hfuse and the lock fuse

atusb/fw/flash.c

@@ -0,0 +1,46 @@
+/*
+ * fw/flash.c - Board-specific flash functions
+ *
+ * Written 2011 by Werner Almesberger
+ * Copyright 2011 Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+
+#include <stdint.h>
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+#define F_CPU   8000000UL
+#include <util/delay.h>
+
+#include "dfu.h"
+#include "board.h"
+
+
+
+void flash_start(void)
+{
+}
+
+
+int flash_can_write(uint16_t size)
+{
+	return 0;
+}
+
+
+void flash_write(const uint8_t *buf, uint16_t size)
+{
+}
+
+
+uint16_t flash_read(uint8_t *buf, uint16_t size)
+{
+	return 0;
+}