diff --git a/firmware/Makefile b/firmware/Makefile
index 5e89d2ab..fe1faf1a 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -23,11 +23,6 @@ PATH_BOOTSTRAP=bootstrap
 PATH_APPLICATION=application
 PATH_BASEBAND=baseband
 
-# TODO: Pass these (as #defines?) to Makefiles, use values in code.
-PAD_BOOTSTRAP=0x10000
-PAD_HACKRF_FIRMWARE=65536
-PAD_BASEBAND=0x20000
-
 TARGET=portapack-h1-firmware
 
 TARGET_BOOTSTRAP=$(PATH_BOOTSTRAP)/bootstrap
@@ -35,6 +30,8 @@ TARGET_HACKRF_FIRMWARE=hackrf_one_usb_ram
 TARGET_APPLICATION=$(PATH_APPLICATION)/build/application
 TARGET_BASEBAND=$(PATH_BASEBAND)/build/baseband
 
+MAKE_SPI_IMAGE=tools/make_spi_image.py
+
 DFU_HACKRF=hackrf_one_usb_ram.dfu
 LICENSE=../LICENSE
 
@@ -56,19 +53,14 @@ program: $(TARGET).bin
 	sleep 1s
 	hackrf_spiflash -w $(TARGET).bin
 
-$(TARGET).bin: $(TARGET_BOOTSTRAP)_pad.bin $(TARGET_HACKRF_FIRMWARE)_dfu_pad.bin $(TARGET_BASEBAND)_pad.bin $(TARGET_APPLICATION).bin
-	cat $(TARGET_BOOTSTRAP)_pad.bin $(TARGET_HACKRF_FIRMWARE)_dfu_pad.bin $(TARGET_BASEBAND)_pad.bin $(TARGET_APPLICATION).bin >$(TARGET).bin
+$(TARGET).bin: $(MAKE_SPI_IMAGE) $(TARGET_BOOTSTRAP).bin $(TARGET_HACKRF_FIRMWARE).dfu $(TARGET_BASEBAND).bin $(TARGET_APPLICATION).bin
+	$(MAKE_SPI_IMAGE) $(TARGET_BOOTSTRAP).bin $(TARGET_HACKRF_FIRMWARE).dfu $(TARGET_BASEBAND).bin $(TARGET_APPLICATION).bin $(TARGET).bin
 
-$(TARGET_BOOTSTRAP)_pad.bin: $(TARGET_BOOTSTRAP).elf
-	$(CP) -O binary --pad-to $(PAD_BOOTSTRAP) $(TARGET_BOOTSTRAP).elf $(TARGET_BOOTSTRAP)_pad.bin
+$(TARGET_BOOTSTRAP).bin: $(TARGET_BOOTSTRAP).elf
+	$(CP) -O binary $(TARGET_BOOTSTRAP).elf $(TARGET_BOOTSTRAP).bin
 
-$(TARGET_HACKRF_FIRMWARE)_dfu_pad.bin: $(TARGET_HACKRF_FIRMWARE).dfu
-	# TODO: Not confident this is reliable. It certainly won't work on Windows.
-	# Pad the .dfu with zeros, then truncate to the desired length.
-	head -c $(PAD_HACKRF_FIRMWARE) /dev/zero | cat $(TARGET_HACKRF_FIRMWARE).dfu - | head -c $(PAD_HACKRF_FIRMWARE) >$(TARGET_HACKRF_FIRMWARE)_dfu_pad.bin
-
-$(TARGET_BASEBAND)_pad.bin: $(TARGET_BASEBAND).elf
-	$(CP) -O binary --pad-to $(PAD_BASEBAND) $(TARGET_BASEBAND).elf $(TARGET_BASEBAND)_pad.bin
+$(TARGET_BASEBAND).bin: $(TARGET_BASEBAND).elf
+	$(CP) -O binary $(TARGET_BASEBAND).elf $(TARGET_BASEBAND).bin
 
 $(TARGET_APPLICATION).bin: $(TARGET_APPLICATION).elf
 	$(CP) -O binary $(TARGET_APPLICATION).elf $(TARGET_APPLICATION).bin
@@ -84,8 +76,8 @@ $(TARGET_BOOTSTRAP).elf: always_check
 
 clean:
 	rm -f $(TARGET).bin
-	rm -f $(TARGET_BOOTSTRAP)_pad.bin
-	rm -f $(TARGET_BASEBAND)_pad.bin
+	rm -f $(TARGET_BOOTSTRAP).bin
+	rm -f $(TARGET_BASEBAND).bin
 	rm -f $(TARGET_APPLICATION).bin
 	$(MAKE) -C $(PATH_BASEBAND) clean
 	$(MAKE) -C $(PATH_APPLICATION) clean
diff --git a/firmware/tools/make_spi_image.py b/firmware/tools/make_spi_image.py
new file mode 100755
index 00000000..a1dc6b1c
--- /dev/null
+++ b/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)