Giotto

1
Giotto

• Embedded Control Systems Development
• with

www.eecs.berkeley.edu/fresco/giotto
Thomas A. Henzinger Ben Horowitz
Christoph M. Kirsch University of California,
Berkeley
(presented by Marius Minea)
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Embedded Systems Development
Application
models derives simulates
Control Engineer
Control Design
Matlab
Functionality Timing
Giotto Program
decomposes implements tests
Software Engineer
Distributed Platform
Giotto!
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Our Approach

• The Time-Triggered Paradigm Kopetz
• -all communication activities triggered by
  clock
• -predictability (i.e., verifiability)
• -safety-critical applications (e.g.,
  automotive)
• TTA hardware protocol realization
• Giotto programming language realization

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Motivating Example Flight Control (DARPA SEC
Program)
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Periodic Tasks
roll control
Sensor tasks
Control tasks
Actuator tasks
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200 Hz
1 kHz
200 Hz
1 kHz
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Modes

• Control system of airplane is designed to operate
  in different modes. In each mode a particular
  set of controllers is deployed. There are
  switches between modes.
• For example
• Navigational modes (taxi, takeoff, cruise).
• Maneuver modes (dive, roll).
• Fault tolerance modes (track which hardware is
  working).

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Giotto

• Giotto is a tool-supported methodology for
  embedded control systems design
• Giotto consists of
• a time-triggered and platform-independent
  programming language
• a compiler
• a runtime library
• Giotto provides an abstract programmers model

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The Giotto Methodology
Giotto Program
Functionality Timing
Compilation
Giotto Executable
Scheduling Communication
Giotto Runtime Library
RTOS, e.g., VxWorks
Distributed Platform
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Task Definition Abstract Syntax
State
f
Input ports
Output ports
Period
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Task Invocation Time-Deterministic Semantics
Task
State
f
Input ports
Output ports
Period 10ms
Time
Read _at_ time t
Write _at_ time t10ms
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Task Invocation Time-Deterministic Semantics
Actual time the task uses the CPU (may be
preempted)
Task
State
f
Input ports
Output ports
Period 10ms
Dont care
Time
Read _at_ time t
Write _at_ time t10ms
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Input/OutputSensors-Control Law-Actuators
State
f
Sensors
Actuators
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Inter-task Communication Connections
P
Q
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Different Periods
Task
P
Q
Q
Time
t
t10ms
t
t5ms
t5ms
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Q-to-Q Connection
P
Q
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Zero-Delay Semantics
Task
P
Q
Q
Time
t
t
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P-to-Q Connection
P
Q
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Zero-Delay Semantics
Task
P
Q
Q
Time
t
t
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Time-Deterministic Semantics
Task
P
Perhaps on same CPU
Q
Q
Dont care
Time
t5ms
t5ms
t
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Time-Deterministic Semantics
Task
P
Q
Q
Time
t5ms
t5ms
t
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Time-Deterministic Semantics
Task
P
Most recent value guaranteed to be available (may
have to be buffered)
Q
Q
Time
t5ms
t5ms
t
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Time-Deterministic Semantics
Task
P
Q
Q
t5ms
t5ms
t
t10ms
t10ms
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An Abstract Programmers Model
High-Level Programming
Giotto
Input/Output Ports
Functionality
Time-Determ. Computation Zero-Delay Communication
Timing
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Giotto Modes
Some Motivations

• Multi-modal control
• Fault tolerance
• Event modeling
• Resource sharing
• Uncertain environments

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Giotto Modes

• A mode is a parameterized set of tasks.
• A Giotto program consists of a set of modes and
  mode switches.
• A Giotto system is in a single mode at any given
  time.

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Abstract Syntax of a Mode
Entry Port
P
1
Q
2
Period 10ms
Frequencies
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Abstract Syntax of a Mode Switch
Connection
M
M
Frequency 2 evaluation of trigger predicate
every 5ms
Trigger predicate
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Mode M
P
1
Connection
Q
2
Period 10ms
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Mode M
P
1
R
4
Connection
Period 10ms
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Concrete Syntax
start m ( ) mode m ( ) period 10 ms
taskfreq 1 do P ( ) taskfreq 2 do Q (
x, y ) exitfreq 2 if y 5 then m ( y
) mode m ( int z ) period 10 ms
taskfreq 1 do P ( ) taskfreq 4 do
R ( x, z )
Tasks are C procedures
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Semantics of the Mode Switch
Task
P
P
Q
Q
R
Mode Switch _at_ t10ms
t10ms
Easy Case
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Semantics of the Mode Switch
Task
P
Q
Time
Mode Switch _at_ t5ms
Interesting Case
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Semantics of the Mode Switch
Task
P
P
Q
R
R
R
t5ms
t5ms
t7.5ms
t10ms
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Mode M
P
1
Connection
Q
2
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Semantics of the Mode Switch
Task
P
Mode switch already finished!
Q
R
R
Time
t5ms
t5ms
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Mode M
P
1
R
4
Connection
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Semantics of the Mode Switch
Task
P
Q
R
R
Time
t5ms
t5ms
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Mode M
P
1
R
4
Connection
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Semantics of the Mode Switch
Task
P
Q
R
R
Time
t5ms
t5ms
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Mode M
P
1
R
4
Connection
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Semantics of the Mode Switch
Task
P
Initial value
Q
R
R
Time
t5ms
t5ms
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Semantics of the Mode Switch
Task
P
Q
R
R
Time
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The Abstract Programmers Model
High-Level Programming
Giotto
Input/Output Ports
Functionality
Time-Determ. Computation Zero-Delay Communication
Timing
Modes
Decomposition
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The Giotto Compiler

• Automatic code generation
• Compilation directives in the form of Giotto
  annotations for distributed platforms

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The Giotto Compiler
Giotto Program

• Two possible answers
• Giotto executable
• Not schedulable

Giotto Compiler
(either because program overconstrained,
or because compiler not smart enough)
Giotto Executable
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Closing the GapGiotto-Architecture Annotations
Giotto Program
Hosts (CPUs), Nets, Worst-case execution /
transmission times
Giotto-A Program
Giotto Compiler
Distributed Platform
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Closing the GapGiotto-Mapping Annotations
Giotto Program
Giotto-A Program
Hosts, Nets, Performance
Tasks to Hosts, Connections to Nets
Giotto-AM Program
Giotto Compiler
Distributed Platform
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Closing the GapGiotto-Schedule Annotations
Giotto Program
Giotto-A Program
Hosts, Nets, Performance
Tasks to Hosts, Connections to Nets
Giotto-AM Program
Tasks to Priorities (say), Connections to TDMA
(say)
Giotto-AMS Program
Giotto Compiler
Distributed Platform
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Platform Dependency
Computation
Task
P
Q
Q
Time
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Giotto-AM
Task
Host A
P
Host A
Host A
Q
Q
Time
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Giotto-AMS
Task
Host A
P
2.
Host A
Host A
Q
Q
1.
1.
Priority
Time
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Platform Dependency
Task
P
Q
R
R
Communication
Time
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Giotto-AMS
Task
Host A
P
Network C
Host B
B
B
Q
R
R
Time slot for connection
Time
t10ms
Real deadline for P!
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The Giotto Runtime Library
Giotto Program
Functionality Timing
Compilation
Giotto Executable
Scheduling Communication
Giotto Runtime Library
RTOS, e.g., VxWorks
Distributed Platform
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The Giotto Runtime Library
Giotto Runtime Library
Scheduling Communication

• Task, connection mapping
• Task priorities
• Connection TDMA slots

Abstraction
RTOS, e.g., VxWorks
Real-Time OS Services

• Timer service
• Scheduling service
• TCP/IP stack

Distributed Platform
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Pure Lego Demo
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Heterogeneous Lego-VxWorks Demo
VxWorks
Lego
Wireless Ethernet Infrared bridge
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Behavior of each Robot
Lead
Someone elses sensor pushed
Stop
Someone elses evading finished
My sensor pushed
Evading finished
Follow
Evade
My sensor pushed
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Soon to Fly GiottoETH Zurich Helicopter