Potential Problems; Troubleshooting Fota - Multitech MultiConnect xDot Developer's Manual

The xDot can tolerate up to 150 lost fragments.
Verification
Once a device completes its fragmented file, it calculates a CRC64 and sends a request to the server to verify the
CRC. The server sends a response indicating if the CRC matches or not. If the CRC is verified the device reboots and
performs the upgrade. If the CRC does not match, the downloaded file is discarded.

Potential Problems

If the Dot misses either setup message, the FOTA session will not be successful. The Dot attempts to receive
both messages multiple times. If the Dot is unsuccessful, it resets the fragmentation sessions and multicast
session.
If the Dot does not receive a CRC response from the Conduit, it resets the fragmentation and multicast
sessions and deletes the fragmentation file.
The Dot can reset the multicast/fragmentation session at any time using AT+FOTA=2.
When using AT+SLEEP, make sure to wake up the Dot before a scheduled FOTA session. Using AT+FOTA=3
will return the time in seconds before the FOTA session is scheduled to start.
If AT+SLEEP is used during the FOTA session, the Dot will miss packets and the session will likely fail.
The FOTA session sends down packets every 1.5 seconds (assuming no duty cycle) and parity packets every
3 seconds by default. For best results, Multitech recommends users suspend all normal Dot operations until
the FOTA session is complete.

Troubleshooting FOTA

Troubleshooting FOTA on the Dot
Problem: Dot does not receive any file fragments.
Troubleshooting:
The Dot must receive two setup messages for the FOTA session to work, fragmentation setup request
and multicast setup request.
Verify if the Dot received the fragmentation setup request. This comes down on port 201. When the
Dot receives this request, it sends an answer. Check the Dot debug log for Sending Fragmentation
Response.
After sending the fragmentation response, the Dot receives a multicast setup request. Check for this
message on port 201. The Dot responds with a multicast setup answer. Check the Dot debug log for
Sending Multicast Response.
Make sure the Dot is in Class C at the start of the FOTA session (AT+DC). The Dot must also be awake
and will not wake up to start the FOTA/Multicast session. The command AT+FOTA=3 displays the time
before a FOTA session starts.
Make sure the Conduit is sending the fragments by checking the Conduit logs in /var/log/log_fota*.
Problem: Dot cannot complete the FOTA session.
Troubleshooting:
If the Dot misses too many packets, the FOTA session cannot be completed.
®
xDot Developer Guide for Japan
FOTA
17