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Project
Flight Tracking and Messaging Systems
(FTMS)
Project Record:
Analysis of Single Board Computer and
Display Board Schematics
Version 1
November 4, 2016
Hoang Nguyen
Samuel Rice
Michael Torres
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Version History
Version
Date
Description/Notes
1
11/4/16
Wrote sections relevant to Analysis Record (Abstract,
Goal, Methodology, Input Specifications, Precision,
Conclusion, References, and Appendix A)
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Table of Contents
Abstract ........................................................................................................................................... 4
Goal ................................................................................................................................................. 4
Methodology ................................................................................................................................... 4
Testing Continuity ....................................................................................................................... 4
Extech 430 Multimeter Continuity Test .................................................................................. 4
Schematic Software ..................................................................................................................... 5
ExpressSCH ............................................................................................................................. 5
Input Specifications ........................................................................................................................ 5
Connection Test........................................................................................................................... 5
Multimeter Continuity Test ..................................................................................................... 5
Precision .......................................................................................................................................... 5
Connection Test........................................................................................................................... 5
Multimeter Continuity Test ..................................................................................................... 5
Conclusion ...................................................................................................................................... 6
References ....................................................................................................................................... 6
Appendix A ..................................................................................................................................... 8
Images of Boards ......................................................................................................................... 8
BL1500 Single Board Computer Upper .................................................................................. 8
BL1500 Single Board Computer Lower .................................................................................. 8
Display Board Upper ............................................................................................................... 9
Display Board Lower............................................................................................................... 9
Appendix B ..................................................................................................................................... 9
Schematics................................................................................................................................. 10
BL1500 Single Board Computer ........................................................................................... 10
Display Board ........................................................................................................................ 11
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Abstract
The Flight Tracking and Messaging System (FTMS) team utilized multimeter continuity tests, as
well as the ExpressSCH schematic drawing software, to map the connections between pins and
ports of the outdated microcontroller and display board. This will allow the team to gain a better
understanding of the functionality and requirements of the old system (Automatic Flight
Following System AFFS 1.0), aiding in the choice of a replacement microcontroller and
reestablishing the connections between the microcontroller and the display board. The
schematics can be found in Appendix B. The team used these schematics to discover there are 48
utilized pins in the old system, which translates into needing a new SBC with the capacity for 48
I/O pins. Finally, the team utilized the schematics to determine the essential connections between
the new SBC and the current display board.
Goal
The Automated Flight Following System (AFFS) Manual contains only a diagram of the location
of the integrated circuits on the single board computer (SBC) and the display boards, with no
connections between the chips shown. In order to better understand the SBC and display board
(shown in Appendix A), especially noting the required number of Input/Output pins and the
connections between the display board and SBC, and their functions in the AFFS system, the
team decided to map out the connections between chips. This will later aid the team in
deciphering the current code, as well as in deciding on a replacement SBC and how to connect
the new board to the display board.
Methodology
Testing Continuity
Extech 430 Multimeter Continuity Test
In order to determine a connection between two or more pins, the team needed to confirm
continuity between said pins. This problem was mostly solved by utilizing the continuity test
function of the Extech 430 multimeters. Using two test probes allowed the team to test for a
connection between two pins. In most cases, one probe was held to one pin while the other probe
was touched to other pins on the board. When the two pins were shown to be continuous, the
connection was recorded on the schematic.
When the aforementioned method failed to show a connection, the traces on the printed circuit
board (PCB) were followed from the desired pin to the termination of the trace, thus showing the
input or output of the pin. This connection could then be added to the schematic. Occasionally,
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there was either no connection or a connection could not be determined. This is displayed on the
schematic as a pin with no connection.
Schematic Software
ExpressSCH
The team evaluated several different options for use as our schematic drawing tool. The drawing
tools we considered included Eagle, ExpressSCH, and DigiKey SchemeIt. The team looked for a
low-cost or free program, which is simple enough to learn quickly. We also wanted a program
which would allow us to create custom components with varying shape and size. Of the three
software programs listed, Eagle costs $69, while ExpressSCH and SchemeIt are free. While all
of the programs appear fairly simple to learn, Eagle had a lot of unnecessary features. At this
point, Eagle was eliminated. SchemeIt requires an internet connection and is an internet program,
while ExpressSCH is downloaded onto the local computer, allowing easier access to the
schematics and custom component library. Between ExpressSCH and SchemeIt, the team chose
ExpressSCH. The program is free, easy to learn and use. The ability to easily create custom
components and add them to a library, which was necessary for the majority of the integrated
circuitry on both the SBC and display board, was incremental in the decision. The team also
knows that the program is utilized by a professional electrical engineer at Cardone Industries.
Finally, utilizing a software program greatly simplifies the task of connecting pins and results in
a cleaner schematic than one drawn by hand.
Input Specifications
Connection Test
Multimeter Continuity Test
The continuity test on the Extech 430 multimeter used has several limits, which could result in
an undocumented connection. The continuity test will only sound the audible signal if the
resistance (measured with the test current of 0.7 mA) is less than 150 Ω. Thus, if the connection
between two pins has a resistor greater than 150 Ω, the continuity test will fail preventing the
team from making a definitive connection between those two pins in the schematic by the
continuity test method.
Precision
Connection Test
Multimeter Continuity Test
Due to the maximum resistance of a path being 150 Ω, any connection between pins having a
resistance greater than the maximum will result in an undocumented connection. This occurs
several times on the SBC. There are numerous 10kΩ resistor network chips on the board, which
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is significantly higher than the maximum level at which the multimeter will detect a connection.
The trace can be followed from one pin to a resistor network IC, but the team cannot determine
which output of the IC is the correct output, as the chips do not have a part or model number that
can be used to acquire a datasheet.
The team also noted that the continuity test reacted differently when a capacitor was contained in
the trace. The meter would emit a short audible signal, then stop, as compared to a continuous
signal for a regular connection. This was mainly resolved by following the traces to the capacitor
and retesting the connection by moving one probe to the other pin of the capacitor.
Conclusion
Utilizing the methods described above, the team mapped out the pins and ports of the AFFS
display board and SBC, as shown in Appendix B. Using these schematics and the datasheets for
the IC, the team will be able to identify necessary connections and pin-outs, aiding in the
understanding of the functionality of the board, as well as collecting important data on specific
requirements of a replacement SBC. We found and confirmed that the total number of I/O pins
involved in processing on the SBC was 48 pins. Of these pins, those connected to pin bank H1
are connected to Ports A and B of one of the Parallel Input/Output chips (chip U6 on schematic).
These ports are 8-bit data buses, which transfer data between the port of the Parallel Input/Output
and a peripheral device. The same is true for pin bank H3, with the pins being connected to Ports
A and B of one of the Parallel Input/Output chips (chip U1 on schematic). Pin bank H2 connects
to input bank J102 on the display board. The pins of J102 are then connected to the pin bank
J104, which is a connector for the modem. SBC bank H1 connects to bank J101 on the display
board. Thus, through H1 and J101 connecting, Port A of chip U6 is connected to the display and
Port B is connected to the LTC1045CN chip, which is a hex translator, receiver, or driver, which
could be used as an LED driver for the display. The H3 and J103 junction connects Port A and
Port B of chip U1 to the display. Thus, we can determine that the commands governing the
display originate on the SBC and are connected to the display via the connections of H1 and
J101, as well as H3 and J103.
The team was unable to detect connections from every pin and port, primarily those that pass
through IC resistors. However, the team was able to connect every input/output (I/O) pin that
connects to the display board from the SBC, fulfilling the need to understand the information that
is passed between the SBC to the display. Those pins left undetermined on the IC of the boards
are not essential to the team’s understanding of the I/O of the boards, and thus it is not an issue
that those pins are connected to unknown places.
References
Extech. "Extech 430 User's Manual." N.p., 2012.
Web.http://www.fondriest.com/pdf/extech_ex430_manual.pdf
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JAARS Inc. Automated Flight Following System Operating Manual. Waxhaw: JAARS, 2004.
Print.
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Appendix A
Images of Boards
BL1500 Single Board Computer Upper
BL1500 Single Board Computer Lower
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Display Board Upper
Display Board Lower
Appendix B
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Schematics
BL1500 Single Board Computer
Figure 1: The SBC
A full-size schematic can be found here.
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Display Board
Figure 2: The Display Board
A full-size schematic can be found here.
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