REALTALK A Programming Language for Wireless Embedded Sensor Networks. Alexandre Bergel. ESUG 2006, Prague

1. REALTALK
A Programming Language for
Wireless Embedded Sensor
Network
Alexandre Bergel
Siobhán Clarke
Distributed Systems Group
Trinity College Dublin

2. Alexandre Bergel
Programming wireless sensor devices is difficult
• Embedded sensor systems are difficult to program.
• Power consumption, memory management, hardware
abstraction:
– component maintenance: the C programming language prevents
software component from being easily maintained.
– sensor asynchronism: sampling is achieved by emitting and
receiving events.
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3. Alexandre Bergel
Sensor sampling creates disruption in the app
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CPU Sensor
Request for a
sampling
answer
measurement
Optimizing
resource
is critical!

4. Alexandre Bergel
Sensor sampling creates disruption in the app
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CPU Sensor
Request for a
sampling
answer
measurement
Data
passing
is critical!

5. Alexandre Bergel
Realtalk: An Object-based language
Goal: making embedded programming easier and providing
advanced hardware abstraction.
Creation of a counter application:
RTObject subclass: #Counter
variableNames: ‘leds timer value’.
Counter compile: ‘start
value := 0.
timer invoke: #triggeredMethod every: 500.’
Counter compile: ‘triggeredMethod
value := value + 1.
leds display: value.’
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6. Alexandre Bergel
Object composition and hybrid type system
Linking the counter to the leds and a timer:
RTObject subclass: #Counter
variableNames: ‘leds timer value’.
Counter composeWith:
{ #leds -> Leds. #timer -> Timer }
Realtalk supports an hybrid type system.
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7. Alexandre Bergel
Class specialization
Let’s emit a sound at each increment:
Counter subclass: #SoundCounter
variableNames: ‘sounder’
aliases: { #triggeredMethod -> #incAndDisplay}.
SoundCounter compile: ‘triggeredMethod
self incAndDisplay.
leds isRedOn
ifTrue: [sounder start]
ifFalse: [sounder stop].’
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8. Alexandre Bergel
Example of Controlled Disruption
Reading two sensors and emitting their sampling:
AnyObject compile: ‘readingTwoSensors
| value1 value2 |
leds display: 1.
value1 := lightSensor read.
leds display: 2.
value2 := soundSensor read.
leds display: 3.
radio emit: (value1 + value2).’
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9. Alexandre Bergel
Method is cut down into pieces...
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Reading two sensors and emitting their sampling:
AnyObject compile: ‘readingTwoSensors
| value1 value2 |
leds display: 1.
value1 := lightSensor read.
leds display: 2.
value2 := soundSensor read.
leds display: 3.
radio emit: (value1 + value2).’

10. Alexandre Bergel
... and those pieces are inserted in a pool
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...

11. Alexandre Bergel
Implementation based on TinyOS/NesC
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Mote/Mica/...
4k RAM devices
TinyOS
NesC Realtalk

12. Alexandre Bergel
Conclusion
• Realtalk is a scripting language dedicated to small sensor
device with high limited resources.
• It provides advanced features regarding:
– component interactions
– component specialization
– sensor programming
• On going work focuses on large software construction.
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