The webinar discussed the GPS clock rollover issue that caused YSI's H-2221 GOES transmitters to display incorrect dates in early 2019 and fail to transmit data. This was due to the GPS receiver reporting 1999 after rolling over from 2099, which the transmitter's firmware interpreted as the year 2099 instead of 1999. As a result, the internal clocks were set to January 1963 instead of the correct date. YSI provided firmware and software updates to fix the issue and prevent it from affecting transmitters with GPS chips that will rollover later. The webinar also offered tips for customers to update their transmitters.

1. AN INFORMATIONAL WEBINAR BY YSI
December 19, 2018

2. The following presentation is protected by copyright
laws and is owned by YSI Incorporated.
© 2018 All rights reserved.
No parts of this presentation may be reproduced or commercially
exploited without express written permission.

3. Dr. Stephanie A. Smith
BACKGROUND
Product Segment Manager, Outdoor
Water Quality
• Defines product requirements for
product development
• Manages WaterLog products
• Ph.D., Microbiology from The Ohio
State University
3 ©2018 YSI, Inc.

4. Steve Parmley
BACKGROUND
Director of R&D
• Oversees all product development
• Responsible for sustaining engineering
and troubleshooting of existing
products
• M.S., Electrical Engineering from the
United State Air Force Institute of
Technology
4 ©2018 YSI, Inc.

5. Zack Henderson
BACKGROUND
Assistant Product Manager, OWQ
• Manages the EXO product line
• Drives product development and
improvements
• B.S., International Business from
Wright State University
5 ©2018 YSI, Inc.

6. Today’s Webinar
1. Timeline: 29 October through 9 November 2018
2. GPS Clock Rollover: The Problem and The Solution
3. 5 Tips for Updating your Transmitter
4. Final Comments
6 ©2018 YSI, Inc.

7. The Timeline

8. GOES Week 1: Problem Identification
8 ©2018 YSI, Inc.

9. GOES Weeks 2-3: Resolution
9 ©2018 YSI, Inc.

10. GPS Clock Rollover
The Problem and the Solution
10

11. Gather data from
attached logger
Stored alarm
date/time from
last successful
transmission
Date/Time
displayed on
LCD screen
The Big Picture
How could GPS cause a GOES transmitter to effectively go off-line?
11
Interdependent systems – GPS, GOES, Real Time Clock (RTC), Firmware
A sequence of events that lead up to the overall system going off-line.
GPS
Receiver
Computation
into full 32 bit
date/time
Sync
GPS time to
GOES
transmission
RTC
RTC vs Alarm
Checks
Prepare 10
second
Package
GOES
Transmission
GPS
Date/Time
Full
Date/Time RTC
Time
to Tx
Activate
Tx
©2018 YSI, Inc.

12. Gather data from
attached logger
Stored alarm
date/time from
last successful
transmission
Date/Time
displayed on
LCD screen
The Big Picture
How could GPS cause a GOES transmitter to effectively go off-line?
12
Key point: GPS time/date is needed to synchronize the onboard Real Time Clock,
such that the GOES radio system can reliably activate and transmit.
GPS
Receiver
Computation
into full 32 bit
date/time
Sync
GPS time to
GOES
transmission
RTC
RTC vs Alarm
Checks
Prepare 10
second
Package
GOES
Transmission
GPS
Date/Time
Full
Date/Time RTC
Time
to Tx
Activate
Tx
©2018 YSI, Inc.

13. Gather data from
attached logger
Stored alarm
date/time from
last successful
transmission
Date/Time
displayed on
LCD screen
The Big Picture
How could GPS cause a GOES transmitter to effectively go off-line?
13
1st root cause to failure
• GPS rollover
• GPS receiver
• NMEA data string
• 10-bit week counter
GPS
Receiver
Computation
into full 32 bit
date/time
Sync
GPS time to
GOES
transmission
RTC
RTC vs Alarm
Checks
Prepare 10
second
Package
GOES
Transmission
GPS
Date/Time
Full
Date/Time RTC
Time
to Tx
Activate
Tx
©2018 YSI, Inc.

14. Gather data from
attached logger
Stored alarm
date/time from
last successful
transmission
Date/Time
displayed on
LCD screen
The Big Picture
How could GPS cause a GOES transmitter to effectively go off-line?
14
2nd root cause to failure
• Firmware interpretation of GPS rollover
• 1999 vs 2099
• Computational standard for representing time/date
• 32-bit signed integer
• “Negative” time and correlation between 2099 and 1963
GPS
Receiver
Computation
into full 32 bit
date/time
Sync
GPS time to
GOES
transmission
RTC
RTC vs Alarm
Checks
Prepare 10
second
Package
GOES
Transmission
GPS
Date/Time
Full
Date/Time RTC
Time
to Tx
Activate
Tx
©2018 YSI, Inc.

15. Gather data from
attached logger
Stored alarm
date/time from
last successful
transmission
Date/Time
displayed on
LCD screen
The Big Picture
How could GPS cause a GOES transmitter to effectively go off-line?
15
Real Time Clock set with incorrect time
• H-552+ LCD shows January 29, 1963
• Time is provided to the GOES radio alarm clock
GPS
Receiver
Computation
into full 32 bit
date/time
Sync
GPS time to
GOES
transmission
RTC
RTC vs Alarm
Checks
Prepare 10
second
Package
GOES
Transmission
GPS
Date/Time
Full
Date/Time RTC
Time
to Tx
Activate
Tx
©2018 YSI, Inc.

16. Details: 1st root cause: GPS receiver
16
GPS Receiver in H-2221 GOES Radio
(National Maritime Electronics Association) NMEA Data
String
• Once per second, the GPS receiver computes a packet of data
containing Latitude, Longitude and so on, and Time and Date.
• HOWEVER, the packet is encoded into a NMEA data string where
the YEAR is simply represented as 2 digits. A portion of the data
string is shown below:
• $GPRMC,120000,A,3948.38,N,8353.22,W,000.0,000.0,211018,020.3,E*68
• Notice the 18 in bold. We will come back to this shortly….
GPS
Receiver
Computation
into full 32 bit
date/time
GPS
Date/Time
©2018 YSI, Inc.

17. Details: 1st root cause: GPS receiver
17
GPS inherent 10-bit rollover
• Data that is sent from the Satellites to the GPS receivers is
limited in time/date information. Time is conveyed by a counter
that increments once per week, and has a maximum of 1024 (10-
bits) unique weeks before it reverts to the 1st week and starts
counting again.
• Additionally, the number of seconds passed within that week is
conveyed.
• The missing information is the epoch or start date/time of the 1st
week at 0 seconds. Each GPS chip manufacturer can choose
their own epoch time.
• The epoch + week counter + seconds into that week allow the
GPS receiver to compute the time/date, and it does so
accurately… for 1024 weeks (19.7 years).
GPS
Receiver
Computation
into full 32 bit
date/time
GPS
Date/Time
©2018 YSI, Inc.

18. Details: 1st root cause: GPS receiver
18
GPS inherent 10-bit rollover (cont.)
• Upon the final week, when the seconds in that week complete
and the week counter increments one last time, it rolls over.
Effectively the time/date regresses backwards 19.7 years.
• On October 21, 2018, the GPS receiver experienced a rollover
event.
• From that moment on, the packet is encoded into a NMEA data
string where again the YEAR is simply represented as 2 digits. A
portion of the data string is shown below:
• $GPRMC,120100,A,3948.38,N,8353.22,W,000.0,000.0,060399,020.3,E*68
• Notice the 99 in bold. The rollover event has induced the GPS
receiver to report 1999.
Actual date 10/21/2018
What the GPS chip will compute after rollover 3/7/1999
just the year 1999
just the last 2 digits as encoded in the NMEA string 99
1999 by itself is
enough to cause
GOES transmission
issues
GPS
Receiver
Computation
into full 32 bit
date/time
GPS
Date/Time
©2018 YSI, Inc.

19. Details: 2nd root cause: Firmware Interpretation of GPS Rollover
19
1999 vs 2099
• The 99 as seen by the firmware in an indicator of the year, with
the assumption that the first 2 digits are 20, as in 2099. This
assumption is a result of the product not being developed or
available for sale prior to the year 2000.
• But a 99 when it was 2018 was unexpected, and the math to add
2000, did so without concern. Thus, 2099.
• But wait, the chase is not over…
Computation
into full 32 bit
date/time
Sync
GPS time to
GOES
Transmission
RTC
Full
Date/Time
©2018 YSI, Inc.

20. Details: 2nd root cause: Firmware Interpretation of GPS Rollover
20
Computational standard for representing time/date
• In order to facilitate the use of a standardized Time/Date format for
use by subsequent sub-systems, the information contained in the
NMEA string is extracted, part by part and assembled into a single
number
• This number represents the number of seconds elapsed since
January 1, 1970.
• December 19, 2018, 11am = 1,545,217,200 seconds
• January 19, 2038, 3:14:08am* = 2,147,483,647 seconds
32-bit signed integer
• A number, between -2147483648 and +2147483647, and when
representing time where the most negative number represents -68
years from 1970 (December 13, 1901), and the most positive
number represents +68 years from 1970 (January 19, 2038*)
©2018 YSI, Inc.

21. Details: 2nd root cause: Firmware Interpretation of GPS Rollover
21
“Negative” time
• Any computational math with a 32-bit signed integer that results in
exceeding the maximum +2147483647 will rollover to -2147483648,
reverting the number to the most negative and count up from there.
• So when the number represents time, one second past January 19,
2038, 3:14:08am will revert time to December 13, 1901, 8:45:52pm.
• 2099 will rollover and then some.
©2018 YSI, Inc.

22. Details: 2nd root cause: Firmware Interpretation of GPS Rollover
22
2099 exceeds 2038  1963
• Maximum signed integer can represent time/date
of January 19, 2038
• 2099 – 2038 = 61 years overshoot
• Or ~ 1.923 Billion seconds past 2038
• Creating a number (~ -223 Million seconds) that
represents January 29, 1963
©2018 YSI, Inc.

23. Details: RTC set with incorrect time
23
H-552+ LCD shows January 29, 1963
• The H-2221 GOES radio module provides the datalogger LCD with
the time.
• The H552+ simply displays the time
• Time then proceeds to pass second for second.
• Initial reports indicated January 29th, whereas later reports placed
the units in early February since a few days had passed.
Time is provided to the GOES radio alarm clock
• The alarm clock, was set to go off an hour after the last successful
GOES transmission, you remember - on October 21, 2018.
• But the current date is in 1963!
• The alarm clock will not ‘ring’ for another 55 years!
• The GOES radio patiently sleeps, waiting to be told to transmit.
Sync
GPS time to
GOES
Transmission
RTC
RTC vs Alarm
CheckRTC
Clock Set:
January 29, 1963
Alarm Set:
October 21, 2018
©2018 YSI, Inc.

24. The Firmware: 2.2.6
24
The firmware is changed to detect a GPS NMEA data string with
a year of 99 or 00 to 17 and process those ‘impossible’ dates.
• This version of firmware did not exist prior to November 2018.
• Those dates imply a GPS 10-bit 1024 week rollover event has
occurred.
• Firmware will first convert a 99 into 1999, or 00-to-17 into 2000-to-
2017.
• Then add 1024 weeks to undo the rollover.
• A GPS date of 99 becomes 1999 becomes 2018.
• As the GPS date increments to 00 and up through 17, the firmware
reports out 2019 through 2037.
The 2nd issue of the date rolling past 2038 is avoided, eliminating
the 32-bit signed integer math issue.
• No 1963 date is miscomputed.
RTC sync time is accurate, LCD is accurate and the GOES radio
alarm clock wakes up the transmitter as expected.
99 03 18
1999 2003 2018
2018 2022 2018
+1024 wk +1024 wk
©2018 YSI, Inc.

25. The Software
25
To facilitate simple firmware upgrade of a deployed H2221 GOES
radio, a software ‘updater’ was created.
The software ‘updater’ takes the firmware and uploads it to the
H2221.
The ‘updater’, being utilized repetitively in the field, needed to be
free of the need for Admin rights on a PC.
• Two version of the updater where created:
• Windows 7
• Windows 10
To install the updater onto a PC, an ‘installer’ was created. This
requires Admin rights, as a fundamental security limitation of
Windows 7 and 10.
Options/requirements
RequiresJava
RequiresAdminforInstall
RequiresAdminforupdater
RunsonWin7
RunsonWin10
v1 FW Y Y Y Y Y
v2 FW Win7 N Y N Y na
v2 FW Win10 N Y N na Y
©2018 YSI, Inc.

26. GPS Week Number Rollover
26
GPS receivers have a pre-
programmed clock rollover every
1024 weeks
Our GPS chips used prior to October
2014 rolled over on 21 Oct 2018
They reverted to January/Feb 1963!
This incorrect date prevented sync
with the GOES satellite
https://www.spirent.com/blogs/positioning/2018/january/gps-rollover-week
©2018 YSI, Inc.

27. 5 Tips for Updating Your
H-2221 Transmitter

28. Tip #1: Read the Instructions!!!
28 ©2018 YSI, Inc.

29. Don’t Fix It if It Ain’t Broke
29
Flowchart from the Instructions at
www.ysi.com/goes-support
Often we’re finding other issues
• Datalogger firmware updated?
• Old signal engineering transmitters
don’t need updates, but might have
other issues
©2018 YSI, Inc.

30. Java Version
30 ©2018 YSI, Inc.

31. Tip #2: Choose your Firmware
31

32. Tip #3: Watch the Video
32
Where can you find this?
www.ysi.com/goes-support of course!
©2018 YSI, Inc.

33. Tip #4: Turn off Scanning
33 ©2018 YSI, Inc.

34. Tip #5: Let Us Help!!
Email info@ysi.com and a technician will call you
Live Chat at www.ysi.com
Call +1 937-688-4255
•Sales and app engineers can come to sites
•Free updates in repair center until 31 December 2018
• Contact info@ysi.com for shipping information
34 ©2018 YSI, Inc.

35. Tip #5: Let Us Help!!
35 ©2018 YSI, Inc.

36. Final Comments

37. What about other GPS chips we’re using?!
GPS chips in our other products are not used for
date info, only positioning
Post-2014 chips: good until 2030-2032
Signal Engineering radios are unsupportable by
YSI if this problem occurs
• In much older models of H-522+ data loggers
37 ©2018 YSI, Inc.

38. GOES Teamwork
Our customers, especially the USGS
YSI R&D, Tech Support, Sales, Marketing,
Quality, Repair Center, Ops…
38 ©2018 YSI, Inc.

39. Questions? info@ysi.com
+1 (937) 767-2762
Contact us: