Generate SPI flash image with Python, not dd/cat/head.

Addresses issue #42.
Windows users now stand a chance of being able to build an image, and all these zero-byte HackRF binary issues should go away.

firmware/tools/make_spi_image.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python
+
+#
+# Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
+#
+# This file is part of PortaPack.
+#
+# 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, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; see the file COPYING.  If not, write to
+# the Free Software Foundation, Inc., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+#
+
+import sys
+
+usage_message = """
+PortaPack SPI flash image generator
+
+Usage: <command> <bootstrap_path> <hackrf_path> <baseband_path> <application_path> <output_path>
+       Where paths refer to the .bin files for each component project.
+"""
+
+def read_image(path):
+	f = open(path, 'rb')
+	data = f.read()
+	f.close()
+	return data
+
+def write_image(data, path):
+	f = open(path, 'wb')
+	f.write(data)
+	f.close()
+
+if len(sys.argv) != 6:
+	print(usage_message)
+	sys.exit(-1)
+
+input_paths = sys.argv[1:5]
+output_path = sys.argv[5]
+bootstrap_image, hackrf_image, baseband_image, application_image = map(read_image, input_paths)
+spi_size = 1048576
+
+images = (
+	{
+		'name': 'bootstrap',
+		'data': bootstrap_image,
+		'size': 0x10000,
+	},
+	{
+		'name': 'hackrf',
+		'data': hackrf_image,
+		'size': 0x10000,
+	},
+	{
+		'name': 'baseband',
+		'data': baseband_image,
+		'size': 0x20000,
+	},
+	{
+		'name': 'application',
+		'data': application_image,
+		'size': len(application_image),
+	}
+)
+
+spi_image = []
+spi_image_default_byte = '\xff'
+
+for image in images:
+	if len(image['data']) > image['size']:
+		raise RuntimeError('data for image "%(name)s" is longer than 0x%(size)x bytes' % image)
+	pad_size = image['size'] - len(image['data'])
+	padded_data = image['data'] + (spi_image_default_byte * pad_size)
+	spi_image += padded_data
+
+spi_image = ''.join(spi_image)
+if len(spi_image) > spi_size:
+	raise RuntimeError('SPI flash image size of %d exceeds device size of %d bytes' % (len(spi_image), spi_size))
+
+write_image(spi_image, output_path)