BAE 5030-503

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

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Data Mask

Soft KeyMask

Implement 1

Implement 2

Implement 3

Implement 1

Implement 2

Implement 3

Kvernland Tellus VT

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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)

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Navigation / GPS

Implement 2

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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

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Soft Key Mask Display

+ + - -

­ ¯

¬ ®

¿

ESC

EditMethod

SoftKeys

Data Mask DisplayNavigationMethod

ControlMethod

Auxiliary

MethodAssignment

200 x 200MinMono

16 or 256Color

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Operator key selection method (Hard Keys)

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

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Soft Key Mask Display

A B C D E F

Text

Go Stop

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VT operator interface component examples

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Soft Keys

Navigation

Touch Screen

Touch Screen

Case IH AFS Pro700

Navigation

Control Method

DICKEYjohn X30Parker ISOBUS VT

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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 Input1

Auxiliary Input2

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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

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WTK ElektronikMulti-Functional-Handle

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VT Alarm Interface Components• Alarm Mask Object

– Defines screen

• Priority– Assignable by Working Set

• When mask is selected by CF– 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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WHEEL FELLOFF!

ALARM

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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

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Object 1 Object ID Type Attributes and Data …Object 2 Object ID Type Attributes and Data …Object 3 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: Requests to Send• Receiver: Clear to Send n-Packets• Sender: Sends cleared packets• …• Receiver: 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

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Output String

Line

Boolean input

Numeric Input

Numeric Output

Input Button

PictureGraphic

List Input

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VT Display Objects

• Input and Output Fields• String• Numeric

• List input

• Shapes• line• rectangle• ellipse• polygon

• Picture Graphic (Bitmap)

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Seeding Rate20,000

Choice #1Choice #2Choice #3

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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)

May 26, 2011