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/boot.c

@@ -0,0 +1,63 @@
+/*
+ * fw/boot.c - DFU boot loader for ATUSB
+ *
+ * Written 2008-2011 by Werner Almesberger
+ * Copyright 2008-2011 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>
+
+#define F_CPU   8000000UL
+#include <util/delay.h>
+
+#include "usb.h"
+#include "dfu.h"
+
+#include "board.h"
+#include "spi.h"
+#include "atusb/ep0.h"
+
+
+#define	MS_TO_LOOPS(ms) ((uint32_t) (ms)*81)
+
+
+static void (*run_payload)(void) = 0;
+
+
+int main(void)
+{
+	uint32_t loop = 0;
+
+	board_init();
+	spi_init();
+	reset_rf();
+
+	/* now we should be at 8 MHz */
+
+	usb_init();
+	dfu_init();
+
+	led(1);
+
+	while (loop != MS_TO_LOOPS(2000)) {
+		usb_poll();
+		if (dfu.state == dfuIDLE)
+			loop++;
+		else
+			loop = 0;
+	}
+
+	led(0);
+
+	run_payload();
+
+	while (1);	/* not reached */
+}