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61 lines
1.6 KiB
Python
61 lines
1.6 KiB
Python
'''
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Helper functions to work with firmware files
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'''
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import base64
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import zlib
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import json
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def bytearray_to_wordarray(data):
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'''Converts an 8-bit byte array into a 16-bit word array'''
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wordarray = list()
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for i in range(len(data) / 2):
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# Calculate 16 bit word from two bytes
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msb = data[(i * 2) + 0]
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lsb = data[(i * 2) + 1]
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word = (msb << 8) | lsb
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wordarray.append(word)
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return wordarray
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def add_checksum(checksum, word):
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'''Simple XOR checksum'''
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checksum ^= word
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return checksum
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def append_checksum(binary):
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'''Calculate and append the XOR checksum to the bytearray'''
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checksum = 0xFFFF
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wordarray = bytearray_to_wordarray(binary)
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# Compute the checksum
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for i in range(len(wordarray)):
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checksum ^= wordarray[i]
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# Add the checksum to the end of the wordarray
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wordarray.extend([checksum & 0xFFFF, (checksum & 0xFFFF) >> 16, 0x0000])
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# Convert the wordarray back into a bytearray
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barray = list()
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for i in range(len(wordarray)):
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lsb = wordarray[i] & 0xFF
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msb = (wordarray[i] >> 8) & 0xFF
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barray.append(lsb)
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barray.append(msb)
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return barray, checksum
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def load_firmware(filename):
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'''Load the image from the JSON firmware file into a byte array'''
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with open(filename, "r") as f:
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desc = json.load(f)
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desc['binary'] = bytearray(zlib.decompress(base64.b64decode(desc['image'])))
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return desc
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def load_binary(filename):
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'''Load binary image file into a byte array'''
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with open(filename, "rb") as f:
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return bytearray(f.read())
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