Download Copy of Headband Datasheet - Oklahoma State University

Design of Engineering Systems Project Report
Title
Headband
Author Names
Steven Welch, Bruce Lebold, Alan Cheville
Submission Date 9/28/09
Summary
 Describe what this product does
 Provide enough background information to put the project in context.
 Describe briefly inputs and outputs of the product (not a technical description).
The Headband is part of the Modular Artificial Gaming Environment. MAGE is a collection of subsystems
that work together to create and implement a real time real life role playing game. The MAGE system
uses several different technologies to communicate with its subsystems and other players. The head
band provides a method of receiving data from an attacking player and displaying some data for the
other players in the game about the player’s health.
The communications from the attacking player will be received using infrared and relayed to the
receiving player's wearable computer using CANbus. The headband will receive a health packet that
indicates the player's health status from the wearable computer and display it using LEDs visible to the
other players in the game.
Instructions
 Submit this report to the SharePoint site in Microsoft Word format. The report should be in Times New Roman or Arial font,
no smaller than 10 point and double spaced.
 Note that all reports are scored on a 100 point scale. If the report is worth more or less than 100 points the score will be
normalized to the points for the course
 DO NOT REMOVE TEXT OR BULLETS FROM UNDER SECTION HEADINGS!
Description
Provide a description of what your device does. Compare what you stated you would do in the proposal to the work you have
actually done. Specifically you should:
 Write down a bulleted list of product features
 Provide a brief technical description (approximately two paragraphs).
 Provide a level 0 functional block diagram. This block diagram should be a physical layout of the product showing the physical
location of connections to the device.
Features:
 One main and two small satellite printed circuit boards each with display LED’s and IR sensors
integrated.
 Satellite boards are connected to main headband board using 8 pin flat flex connectors.
 Three colors of LEDs (red, yellow, green) indicate player health status. LED’s flash to indicate
critical health conditions.
 Headband uses standard 38 kHz, 950 nm surface mount IR sensors (Vishay TSOP36138).
 Headband system connects to MAGE using CANbus [2].
 System is powered directly from CANbus, no on-board power is needed.
Technical Description:
The headband is an accessory to the MAGE gaming system [1] that is used both to detect incoming IR
data packets and visibly display player health. The headband system consists of one main
communication and processing board and two satellite display and detector boards. Infrared light data
packets are detected by the IR sensors, and the data packet is then read by an onboard microcontroller.
The microcontroller then relays the incoming data packet over CANbus to the MAGE system. The MAGE
system responds by sending the headband an 80 bit packet that contains player health. For details on
data packet format see the MAGE system documentation. When a properly formatted data packet is
received over CANBus the headband microcontroller lights red, yellow and/or green LED’s on the main
and satellite boards to visually display player health status. Details on the LED status indicators are
given in the Principles of Operation section under the Detailed Technical Description.
The headband boards and connecting cables are mounted onto a hat or other headgear by the user. In
use the headband is mounted around the head with the three boards equally spaced at approximately
120. The use of three IR sensors allows detection of incoming radiation over 360. Beyond the CANbus
interface, LED’s and IR detectors, the headband processor board also has a Brainstem RS-232 port for
debugging and a SIP header for programming the microcontroller as shown in the figure below.
Level 0 Functional Block Diagram of Headband:
Figure 1 - Diagram of Headband main board showing system inputs and outputs
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Product Block Diagram and pin out diagram.
 On one sheet of paper provide a level 1 functional block diagram of your product.
 On a separate sheet of paper provide a pin out table. The pin out table should match the Reference Designators from your
layout and also the terminology used in your level 0 block diagram.
LEDs:
R,G,Y
Main Board
Satellite
HIU
38 kHz
IR
Transmission
LEDs:
R,G,Y
2 wire differential
pair
LED Drivers:
Operate R,G,Y
LEDs based on 3
PIC outputs
38 kHz
IR
Transmission
CAN bus:
Provide CAN
connection to HIU
IR Receivers:
38kHz modulated
IR Receivers:
38kHz modulated
Satellite
38 kHz
IR
Transmission
LEDs:
R,G,Y
AND Gate
PIC 16F688
IR Receivers:
38kHz modulated
Brainstem
Connector
Figure 2 - Headband Level 1 Block Diagram
3
5V Power
Programming
Header
Table 1- Programming Header
RefDes Pin
I/O
Description
U21
1
I
MCLR
2
Power
+5V
3 Ground
0V
4
I
PGD
5
I
PGC
6
NA
NC
Table 2- Satellite Boards
RefDes Pin
I/O
Description
U4,U8
1
NA
NC
2
NA
NC
3
O
Green
4
O
Yellow
5
O
Red
6
I
IR Data
7
Power
+5V
8 Ground
0V
1
Tabel 3- CANbus
RefDes Pin
I/O
Description
U7
1
Power
+5V
2
I/O
CAN Low
3
I/O
CAN High
4
NA
NC
5 Ground
0V
Table 4- CANbus
RefDes Pin
I/O
Description
J1
1 Ground
0V
2
Power
+5V
3
I/O
CAN High
4
I/O
CAN Low
Table 5- Brainstem Header (TTL-RS232)
RefDes Pin
I/O
Description
U20
1
I
Headband Receive
2
Power
+5V
3
O
Headband Transmit
4 Ground
0V
Table 6- Test Points
RefDes Pin
I/O
Description
U6
1
Power
+5V
U12
1
I
ANDed IR Data
U14
1 Ground
0V
Detailed Technical Description:




Describe the principles of operation of your device in detail.
Provide a brief description of the signals at all inputs, outputs and internal test points.
Describe the test procedures used to verify proper device operation.
Provide a brief description of debugging techniques and common problems the user might encounter with your device.
Principles of Operation
The headband has two functions in the MAGE system. It displays a player’s health status and receives
MAGE packets that have been sent through IR transmission.
To display the health status, the headband waits for a MAGE packet on the CAN buffer. The packet must
be properly formatted or it will be ignored. The Team ID Value must be 255, the player ID value must be
0, and the Process ID value must be 0,1,2,3, or 4. Other values are ignored. Each Process ID correlates to
a different light sequence:





0: Green and Yellow steady
1: Yellow steady
2: Red and Yellow alternating then steady
3: Red flashing then steady
4: Green steady
To receive IR transmissions, the headband uses a protocol created within the IR.h header file in the
MAGE code. The IR transmission is a 38kHz modulated signal. At the transmission side a period with two
sets of pulses represents a 0 and a period with no signal represents a 1. The transmission protocol
requires a start sequence of one set of pulses followed by 64 bits of data contained in the MAGE packet.
Figure 3 shows an example of the first four bits of a transmission.
Figure 3 - Example Transmission
The IR receiver output is active low, so when a 38 KHz modulated signal is being received the output is
0V. Otherwise the output is 5V. The receiver has open-collector outputs with a built in pull-up resistor
which causes two high-to-low transitions when the transmission for 0 is received. The output should
remain at 5V if a 1 is received. The start transmission causes the receiver to create one high-to-low
transition. The IR packet is decoded by interpreting the high-to-low transitions driven by the output of
the IR receiver. Figure 4 shows the output of the IR receiver after receiving the signal from Firgure 3.
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Figure 4 - Receive Example
Description of Signals
During normal operation the programming header and brainstem connector are unused, however the
power and ground pins are active and can be used. All power and ground pins are tied to the power and
ground of the headband supplied through the CAN connection.
The satellite board connectors have a pin to power each LED which should output 5vdc whenever the
LED is set on according to the light sequences. The IR data input will normally remain at 5vdc until
modulated IR is received. Pull-up resistors on the inputs to the AND gate insure that if a satellite board is
disconnected, data from the other IR receivers will still be decoded correctly.
The CAN bus connections have power and ground pins which supply the headband with power. For
current draw with different combinations of LEDs, refer to Table 14. There are also CANH and CANL
which is a differential pair used to transfer data packets between all devices attached to the MAGE
system.
Test Procedures
When powered on, the headband should show a light sequence where all LEDs turn on, one after
another, then turn off in the same order.
In order to verify the CAN hardware has properly initialized, you may connect a brainstem serial
interface connector [3] to the headband. If the headband prints any messages, the CAN hardware has
initialized. To further test the CAN functionality, send a headband packet, as described earlier, over
CANbus. This can be done using the testing terminal on the HIU or by setting up a test PIC and CANbus
module to send packets. If the correct light sequence is displayed, the CAN is working properly.
Technical details on CANbus can be found in [4].
In order to test the IR you may use the mage system HIU [1] or a brainstem. When any IR data is
received it will be printed over RS-232 through the brainstem connector at 9600 baud. The default
settings in SIOW are used which include one start bit of 0 and one stop bit of 1. The IR data will also be
sent over CAN. If the HIU is connected, it will print the received packet over its USB connection. This test
will also demonstrate the functionality of the CANbus on the headband. For more information please
refer to MAGE system documentation.
Debugging
A problem with the headband may occur if any hardware changes occur. This could affect the timing of
the IR decoding. . If IR data is consistently incorrect, try adjusting the PERIOD definition in IR.h..To adjust
the PERIOD, first measure the actual time of a one bit transmission from your IR transmitter. Then start
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by setting PERIOD that the measured time and reduce it by 5 each time until the data received is
accurate. The current value is 1950. Some users have reported that ambient light, particularly
fluorescent light fixtures, interferes with reception of data packets. It may be worthwhile to test the
system in a dark room if continued data reception problems are encountered to eliminate ambient light
as a source of error.
IR data packets can be monitored through a dedicated test point, refer to Table 6. An IR transmitter
using the protocol in IR.h is needed to test the IR functionality. If one is not available, a PIC could be
programmed to mimic the signal as it is given by the IR receiver. This signal would need to be applied to
the IR Data test point. Note that for simple on-off test of the receiver a 950 nm LED modulated by a 38
kHz square wave from a function generator will suffice.
Tables of Detailed Technical Specifications (15 points)
Describe the models, drawing, simulations, etc. that your team used to understand and make predictions about your design
project. You should write one to three paragraphs on each of the points below:
 List in tables measured values of all input and output pins to the device during normal operation.
 Provide graphs or figures of any:
o Measured time dependent inputs, outputs, and signals at all test points.
o Measured change in output with changing input parameters (e.g. Variation of gain with operating voltage for an
amplifier)
o Considering all components used list the Absolute minimum and maximum operating ranges.
Tables 7-12 show the measured voltages at each pin during idle use with a 5.001V supply.
Table 7- Programming Header
Description Measured Voltage
MCLR
4.936
+5V
4.999
0V
0.001
PGD
0.002
PGC
0.002
NC
NC
Table 10- CANbus
Description Measured Voltage
0V
0.000
+5V
5.001
CAN High
2.992
CAN Low
2.067
Table 11- Brainstem Header
Description
Nominal Voltage
TTL Receive
2.020
+5V
5.000
TTL Transmit
5.000
0V
0.002
Table 8- Satellite Boards
Description Measured Voltage
Green
0.140
Yellow
0.140
Red
0.140
IR Data
4.994
+5V
4.998
0V
0.002
Table 12- Test Points
Description Measured Voltage
+5V
4.999
IR Data
4.997
0V
0.002
Table 9- CANbus
Description Measured Voltage
+5V
5.001
CAN Low
2.067
CAN High
2.992
0V
0.000
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Table 13 - Table of maximum/minimums for
the Headband
Supply Voltage
Continuous
Current
Time to update
LEDs
IR receive rate
Min
4.5V
0.018A
Max
5.5V
0.126A
5 sec
NA
400 bps
400 bps
Table 14 – Current Draw (mA) With Different
LED Sequences
0 LEDs 1 LED 2 LEDs 3 LEDs
No Satellites 17
33
48
57
1 Satellelite 18
50
80
98
2 Satellites
19
67
112
139
Figure 5 - IR Data Tx/Rx
The figure above shows the result of IR test transmission that shows the transmission and reception of
IR data. The bottom waveform is the 38kHz modulated signal transmitted by the IR LED. The top
waveform shows the reaction from the IR receiver. Sending a 38kHz square wave cause the receiver to
output low after a 200 us delay. Seizing transmission then causes the receiver to go high after a 300 us
delay. Each time the receiver output goes low, an interrupt is driven on the PIC and the IR signal is
decoded.
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Detailed application information
You should write one to three paragraphs on each of the points below:
 Describe in detail how to use the device
 Describe in detail how to connect the device to other systems
 Describe common fault conditions and how to correct them
 Describe any variable voltages, resistances, currents, or any other user selectable hardware features
 Describe if necessary how to calibrate the device and or test for proper operation.
 Describe how to program any onboard memory or microprocessor
Device Usage
To use the headband only one connection is needed. A connection to CANbus (USB or legacy 0.1" SIP
header connectors) supplying 5V is required for minimal operation. The current design fully supports a
CAN connection to the HIU (version 3.2 or newer). After connecting the headband to the HIU and
powering on the HIU, the headband will be fully operational. It will be waiting for CAN packets indicating
a health status to display as well as IR packets to be echoed over the CAN bus.
Modular Usage
It may be desirable to use the headband for some other purpose than MAGE. The headband could act as
an IR receiver for any system using CAN bus or RS-232 to communicate with devices. Either connection
the CAN connector or the brainstem connector, will provide power to the headband as well as a means
of communication
To use the headband as a modular device, some modifications to the code may be necessary. If using
the RS-232 connection the firmware will need to be modified. Also, the IR communication protocol is
unique to MAGE, so any pre-existing protocol will need to be added to the headband firmware.
Fault Conditions
The most common fault condition is the reliability of the IR data. The MAGE packet has a built in
checksum that can be used to verify data is correct. Data could be incorrect for several reasons:
interference from other light/IR sources, multiple simultaneous IR transmissions, or an incorrect PERIOD
setting in the IR.h code. If IR data is consistently incorrect, try adjusting the PERIOD definition in IR.h..To
adjust the PERIOD, first measure the actual time of a one bit transmission from your IR transmitter. Then
start by setting PERIOD that the measured time and reduce it by 5 each time until the data received is
accurate. The current value is 1950.
User Selectable Hardware
The headband has one user selectable hardware feature. There is a set of DIP switched on the board.
Switch 1 activates/deactivates a 120 Ohm termination resistor across the CANH and CANL pins. Normally
this should be left on. If another device on the CAN bus provides a termination the switch should be
off.(Switch 2 is unused)
Calibration and Testing
If the CAN bus is improperly terminated, communication may fail sometimes or consistently. If the IR
PERIOD is set incorrectly data will be interpreted incorrectly. Calibrations that may be required include
enabling/disabling the CAN termination resistor and setting the IR PERIOD definition in the IR.h header
file. Both of these processes are outlined previous to this section.
When powered on, the headband should show a light sequence where all LEDs turn on, one after
another, then turn off in the same order. A visualization of the LED startup pattern is shown below.
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Figure 6 - LED Start Sequence
To test the CAN functionality, send a headband packet, as described earlier, over CANbus. This can be
done using the testing terminal on the HIU or by setting up a test PIC and CANbus module to send
packets. If the correct light sequence is displayed, the CAN is working properly.
In order to test the IR you may use an HIU or a brainstem. When any IR data is received it will be printed
over RS-232 through the brainstem connector at a baud rate of 9600 bps. It will also be sent over CAN. If
the HIU is connected, it will print the received packet over to the terminal through its USB connection.
This test will also demonstrate the functionality of the CANbus on the headband.
Programming the Microcontroller
To program the PIC16F688 on the headband follow the steps listed below:
 Remove the two LED jumpers
 Power the headband from an external power supply or by connecting it to an active CAN
connection.
 Open MPLAB
 Select the proper device(pic16f688)
 Select the ICD 2 Programmer
 Import the .hex file you wish to program to the headband
 Insure the ICD Programmer is connected to the computer’s USB port
 Connect the programmer to the programming header
 Click the program button in MPLAB and wait for completion
 Replace LED jumpers
 Remove programmer from programming header
Application Example
 Describe in detail an example of how the device would be used by the end user.
 Provide a connection diagram specifying needed hardware, cables, power supplies, etc.
The headband and its satellite boards will need to be mounted in some sort of headgear to be worn by
the user. This allows IR transmissions to be received by the user and makes the health status visible to
other players. The IR receivers were designed to be placed around the user’s head at 120 degree
intervals to allow IR reception from any direction. This should be considered when mounting the
headband in headgear.
The headband board is mounted by four 1/8 inch through holes. The two satellite boards are also
mounted through four 1/8 inch holes. The mechanical dimensions and hole spacings are shown in the
figures below.
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Figure 7 - Headband Mounting
Figure 8 - Satellite Mounting
The headband is intended to be used as a peripheral in MAGE. It acts as a receiver for IR packet
transmissions and as a health status display to other players. Using the headband with MAGE requires
the headband be connected to the HIU through a CAN connector. This will power the headband and
provide a communication channel between the devices. A connection diagram for the headband in the
MAGE system can be seen below[1].
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Figure 9 - Connection Diagram
References
Use the IEEE Style. Details can be found on the course web site or in the IEEE Authors Manual. References must be cited in the
body of the text.
[1] Oklahoma State University, “Gaming System Headband,” MAGE System Headband, 2009. [Online].
Available:https://stillwater.sharepoint.okstate.edu/ecendesign/projects/Headband/Shared%20Docume
nts/Gaming%20System%20Headband.docx. [Accessed: Oct. 4, 2009].
[2] Baker, B. C., "Ease into the Flexible CANbus Network", Microchip Analog Design Note ADN004, 2003
[Online]. Available: http://ww1.microchip.com/downloads/en/DeviceDoc/adn004.pdf [Accessed, Oct.
9, 2009].
[3] Brainstem connectors convert TTL serial to RS-232 levels and are manufactured by Acroname
Robotics. More information can be found at Acroname's web site [Online]. Available:
http://www.acroname.com/robotics/parts/S13-SERIAL-INT-CONN.html [Accessed Oct. 29, 2009].
[4] Richards, P., "A CAN Physical Layer Discussion", Microchip Application Note AN228, 2002 [Online].
Available: http://ww1.microchip.com/downloads/en/AppNotes/00228a.pdf [Accessed, Oct. 9, 2009].
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Appendix
 Provide any relevant diagrams, schematics, PCB Layouts, Code, or other technical documentation.
All current headband code will be located at:
https://launchpad.net/headband/+download
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Figure 5 - Headband Schematic
Figure 10 - Headband PCB Layout
Figure 11 - Satellite Schematic