Communications Electronics for Ag. Machines
ISOBUS
Lecture 8 ISO 11783 Part 6 / Virtual Terminal
BAE 5030 – 503
Summer 2011
Instructor: Marvin Stone
Biosystems and Agricultural Engineering
Oklahoma State University
May 26, 2011
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Virtual Terminal (VT) Concept
• Serves as a “human interface” between operators
and “implements” on an ISO 11783 bus
– VT provides both output (display) and input (buttons and
controls) functionality to the operator
– A Working Set, a CF or Group of CFs, composes the logical
entity that represents the implement that the operator
interacts with
– VT provides a standardized means for displaying information
and receiving operator input from a Working Set
• VT appears as exclusively available to a particular implement
but multiple implements may use terminal simultaneously
• An Implement using the terminal is not necessarily aware of
other Implements using the VT.
– Operator may switch the active panel and key inputs from
one Implement to another.
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Virtual Terminal (VT) Example
• Planter and Sprayer Simultaneously use Terminal
– Operator can switch to see either planter or sprayer
– planter or sprayer each have complete use of the terminal and
may be unaware of each other
– Many other implements may also be connected, eg. tractor,
GPS guidance system, task controller
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Example Virtual Terminals
• A method on the terminal may be used to switch
implements
Implement 1
Implement 2
Implement 3
Implement 1
Kvernland Tellus VT
Implement 2
Implement 3
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Working Set Definition
• Working Set consists of a group of CFs created by
one manufacturer and designed to work together as a
single entity
• After Power-ON and successful Address claims each
Working Set Master sends a stream of messages to
the VT identifying:
– Master and number of members
– Each member of the working set
– The VT allows a Working Set Master and its members as a
set to connect and use the terminal
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Network Model for VT Communications
•
•
•
Working sets consist of at least one master and may have slave CAs
The VT communicates with the WS master. WS Master and slaves
download Object Pool elements and interact with the VT.
VT replies are sent to the WS Master (except configuration 4 and later
are sent to the originator)
Implement 2
Navigation / GPS
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Connection management
• The VT when it is functional on the bus sends the VT Status
message on change of status and once per second.
– Working Sets use this message to determine that the VT is
operational and not busy.
– Loss of this message for longer than 3 seconds indicates to the WS
that the VT has been turned OFF or is disabled.
• The Working Set Maintenance message is sent by the WS to
the VT once per second when the working set has initialized
– VTs use this message to determine when the WS is operational
– Loss of this message for longer than 3 seconds indicates to the VT
that the WS has been turned OFF, removed or disabled. If this is
an unexpected shutdown, the WS’s object pool is deleted.
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Typical VT initialization message traffic
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VT operator interface components

Data Mask Display
200 x 200
Mono
Min
16 or 256
Color


++
-
ESC
Soft Key Mask Display
Control
Method
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Edit
Method
Auxiliary
Assignment
Method
Soft
Keys
May 26, 2011
Navigation
Method
Soft Keys
• Soft Key Mask created by Working Set is used to define
displayable information and Key Code
• One set of Keys (a Mask) may be selected at a
time by the Working Set
• VT provides for methods of scrolling keys if virtual softkeys are
provided
• VT informs WS of available keys in Metrics response
• Working Set controls menu hierarchy
Soft Key Mask Display
Text
A
B
C
Go
Sto
p
D
E
F
Operator key selection method (Hard Keys)
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VT operator interface component examples
Case IH AFS Pro700
Navigation
Touch Screen
Soft Keys
Touch Screen
Control Method
Parker ISOBUS VT
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Navigation
DICKEYjohn X30
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VT Interface Components
• Auxiliary Input (Optional)
• May be built into VT or remote
• Working sets may contain Auxiliary
Inputs and/or Auxiliary Functions
• Messages included to allow VT to:
assign Auxiliary Inputs to
Auxiliary Functions
– Auxiliary Input Types include
• Boolean ON/OFF and ON/OFF/ON
– Latched
– Non-Latching
– Etc.
• Analog
– Return to 0%, 50%,
• Quadrature
• Bi-directional encoder
• Touch screen / Mouse Support
– Button Object
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Auxiliary Input
1
Auxiliary Input
2
Auxiliary functions
• Auxiliary functions allow operator to control specific functions
independent of the VT screen interface
• Auxiliary inputs (keys, switches, dials, knobs, sliders),
provided by one or more working sets (or the VT), are active at
all times after being assigned to an auxiliary function
• Auxiliary inputs are assigned to auxiliary functions (i.e.
raise/lower, start/stop, set position) and are also provided by
one or more working sets (or the VT).
• The operator assigns the inputs to the functions using a
proprietary auxiliary assignment screen provided by the VT
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•
•
•
•
Auxiliary Function Example
Implement (working set) provides a “raise/lower
implement” auxiliary function
An auxiliary input, a two position momentary toggle
switch, located on the armrest of the tractor
(associated with the tractor ECU working set) of a
type that is compatible with the auxiliary function is
available
The operator, using a screen provided by the VT,
assigns this switch to the “raise/lower implement”
function.
The function of the switch does not change unless
changed by the operator
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Auxiliary Function Assignment
• Working Set masks contain Auxiliary Input objects
• Working Set masks contain Auxiliary Function objects
• A protocol is provided to allow WS to announce status of both
auxiliary inputs and auxiliary functions
• VT provides a proprietary screen with auxiliary object designators
(provided in the WS object pools) to allow operators to assign
auxiliary inputs to functions
– VT uses any stored previous assignments
• VT notifies Working Set of assignment of Input Functions to
Objects
• Working Set acknowledges
• Operator may re-assign Input Functions
WTK Elektronik
Multi-Functional-Handle
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VT Alarm Interface Components
• Alarm Mask Object
– Defines screen
ALARM
• Priority
– Assignable by Working Set
• When mask is selected by CF
WHEEL FELL
OFF!
– VT overlays entire Data Mask Area
– Active alarm masks are ordered highest priority first, then first
alarm first
– Soft Keys can be used when the alarm is active
– Some acknowledgement method used to clear the alarm
• Acoustic Alarm Signal Object may be included
– Selectable duration, frequency, repetition, volume
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VT Language management
• Language Message
– VT (virtual terminal) sends this message after the system
has completed its power-on and address claims
– A default language is stored in the Tractor ECU and
retrieved by the VT in case the desired language is not
supported by the implement ECUs.
– The VT shall provide a method for the operator to view the
supported language list of a connected implement or
implement pool and to select a language from this list.
– Contains language code, number format, decimal symbol,
date format, units for common parameter types, and units
system
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VT protocol Messages
• Destination specific group function message
– VT identifies sender via Source Address
– ECU identifies VT via Source Address
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Communication of Object Pools to a VT
• Pool is Encapsulated in Transport Protocol
– One or more sessions may be used but only one type of TP
• Message sent to begin the pool is the:
– Object pool transfer message with a data field that contains VT Objects
• The message sent to finalize transmission of the pool is the:
– End of Object Pool message
• The VT responds with the:
– End of Object Pool response message
• Pool is a Collection of Objects in the data field of the Object
Pool Transfer message
Object 1
Object 2
Object 3
Object ID Type Attributes and Data …
Object ID Type Attributes and Data …
Object ID Type Attributes and Data …
…
And so on
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VT Object Transport Protocol
• Used for pool transfer and for any 9 byte or longer
messages
• Uses both standard Transport Protocol and Extended
Transport Protocol
– Multi-packet message protocols
• Standard: Up to 1785 bytes message data
• Extended: 1786 to 117,440,512 bytes message data
– Connection management
•
•
•
•
•
Sender:
Receiver:
Sender:
…
Receiver:
Requests to Send
Clear to Send n-Packets
Sends cleared packets
Acknowledges completion
– Missed packets may be requested by receiver
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Extended Transport Protocol
•
•
•
Uses existing Connection Mode Transport Protocol with additional
extended functions (BAM may not be used)
Can transport up to 117,440,512 bytes (117 M bytes)
Uses a sequence number offset to increase the range of packet
sequence numbers
– Actual extended message sequence number = (ETP.DT Sequence number
+ ETP.CM_DPO Data Packet Offset)
– The ETP.CM_DPO Data Packet Offset is sent after every Clear to Send
(ETP.CM_CTS) message to provide the extended sequence number
•
Four new control functions are defined to distinguish the Extended
Transport Protocol from the normal Transport Protocol
–
–
–
–
Control Byte 20 Extended message Request To Send (ETP.CM_RTS)
Control Byte 21 Extended message Clear To Send (ETP.CM_CTS)
Control Byte 22 Extended message Data Packet Offset (ETP.CM_DPO)
Control Byte 23 Extended message End of Message Acknowledgment
(ETP.CM_EOMA)
• Standard connection abort message is retained
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Message sequence for the Extended Transport Protocol
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Screen Description
• A mask
defines
screen and
contains
objects that
describe
screen
elements
• A mask can
define data
screens,
softkeys or
alarms
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Example screen objects
Output String
Line
Boolean input
Numeric Input
List Input
Picture
Graphic
Numeric Output
Input Button
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VT Display Objects
• Input and Output Fields
• String
• Numeric
• List input
Seeding Rate
20,000
Choice #1
Choice #2
Choice #3
• Shapes
•
•
•
•
line
rectangle
ellipse
polygon
• Picture Graphic (Bitmap)
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Complex Graphic Objects
• Meter Object
• Bar Graph Object
• Arched Bar Graph
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WS updating a numeric display on a VT
• Numeric value on the display can be updated with two CAN
packets
• The VT responds and indicates if any error occurred
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Changes in object attributes
• May be through commands from the WS or through
event triggered macros
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Events signaled from the VT to the WS
•
VT Events including soft key press, button press, input object select,
pointing events, escape, change numeric value, change Mask, change
soft key mask, change string, hide/show user layout, and audio signal
termination signal the WS through a message.
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Storage Management in a VT
• Commands
– Get Versions
– List of all
version labels
for Working
Set.
– Store Version (by
Label)
– Stores volatile
resources of
Working Set.
– Load Version (by
Label)
– Delete Version (by
Label)
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