def chunkData(bfr):
	"""
	Analyze the 64k buffer, find all 128Byte chunks that are in use (have data != to -1)
	Will return a list of 512 entries with "1" meaning block of 128Bytes had data chaned and "0" no data changed
	"""
	mapped=[]

	for i in range(0,len(bfr),128):
		chunk = bfr[i:i+128]			# split buffer into 128 Bytes chunks
		
		used = False

		for cell in chunk:				# if any byte changed, mark chunk for upload
			if cell >= 0:
				used = True
		
		if used:
			mapped.append(1)
		else:
			mapped.append(0)

	return mapped