I want to recover DFU over BLE upon a dropped connection while in the middle of an update.
I have my own software that I've cooked up to program from another NRF52 chip and I've tested with nrfutil the following scenarios:
- Start secure DFU, force-stop host program so that target times out due to inactivity and re-advertises as 'DfuTarg'
- Start secure DFU, unplug power to DFU target
In both scenarios, I am able to read offset and crc of the init packet that was sent before above events, skip re-sending the init packet, and jump right into sending image packets.
However, I am unable to read my last image offset from before these events and recover from that point, which is what I want to do so that I spend less time re-sending packets when dropped connections can occur.
I would post some of my code, but I am unable to recover even when using nrfutil application that has code showing a recovery method that doesn't seem to work either...
def try_to_recover():
if response['offset'] == 0:
# Nothing to recover
return
expected_crc = binascii.crc32(firmware[:response['offset']]) & 0xFFFFFFFF
remainder = response['offset'] % response['max_size']
if expected_crc != response['crc']:
# Invalid CRC. Remove corrupted data.
response['offset'] -= remainder if remainder != 0 else response['max_size']
response['crc'] = binascii.crc32(firmware[:response['offset']]) & 0xFFFFFFFF
return
if (remainder != 0) and (response['offset'] != len(firmware)):
# Send rest of the page.
try:
to_send = firmware[response['offset'] : response['offset'] + response['max_size'] - remainder]
response['crc'] = self.__stream_data(data = to_send,
crc = response['crc'],
offset = response['offset'])
response['offset'] += len(to_send)
except ValidationException:
# Remove corrupted data.
response['offset'] -= remainder
response['crc'] = binascii.crc32(firmware[:response['offset']]) & 0xFFFFFFFF
return
self.__execute()
self._send_event(event_type=DfuEvent.PROGRESS_EVENT, progress=response['offset'])
