Raspberry Pi and the Embedded Domain Omer Kilic || @OmerK - - PowerPoint PPT Presentation
The Actor Model applied to the Raspberry Pi and the Embedded Domain Omer Kilic || @OmerK omer@erlang-solutions.com Agenda Current state of Embedded Systems Overview of the Actor Model Erlang Embedded Project Modelling and
Omer Kilic || @OmerK
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An embedded system is a computer system designed for specific control functions within a larger system, often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user needs.
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Source: http://embedded.com/electronics-blogs/programming-pointers/4372180/Unexpected-trends
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– Connected and distributed systems
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– No underlying OS or high level abstractions
– Minimal interrupt and switching latency, scheduling guarantees, minimal jitter
– Slimmed down Linux with hardware interfaces
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– Shared memory
– Pre-emptive: event driven – Round-robin: time multiplexed
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to abundant supply of cheap boards
– Raspberry Pi, Beagleboard/Beaglebone, Gumstix et al.
new territory for embedded engineers
– No direct mapping for RTOS concepts, especially tasks
– Here be dragons
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– “Universal primitives for concurrent computation”
concurrent systems
languages
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– Messages kept in a mailbox and processed in the
– Make local decisions and change internal state – Spawn new actors – Send messages to other actors
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– Specific to language and library implementation
problematic for certain applications
– Ordering of messages received from multiple processes – Abstract definition may lead to inconsistency in larger systems
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Erlang Solutions and University of Kent
– Aim of the project: Bring the benefits of concurrent systems development using Erlang to the field of embedded systems; through investigation, analysis, software development and evaluation.
http://erlang-embedded.com
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companies
– Originally designed for embedded applications
systems out of the box
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supervision hierarchies
– Isolation of Actors
– Hot code loading
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spawn(math, fact, [5])
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Pid1 Pid2
math:fact(5)
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{Pid1, msg}
Pid1 Pid2
Pid2 ! {self(), msg}
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Pid1 Pid2
link(Pid2)
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– Abstract error handling away from the modules – Results in leaner modules
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PidA PidB PidC {'EXIT', PidA, Reason} {'EXIT', PidB, Reason}
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PidA PidB PidC {'EXIT', PidA, Reason}
process_flag(trap_exit, true) Slide 22 of 45
ports used to interface external world to the Erlang runtime.
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(flickr/dereckesanches)
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Video, 3.5mm Stereo Jack, DSI, CSI-2)
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UK registered charity.
the study of computer science and related topics, especially at school level, and to put the fun back into learning computing."
Future Engineers/Programmers!
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(flickr/lebeus)
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– Faster, needs root, potentially dangerous!
– Slower, doesn’t need root, easier, relatively safer
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init(Pin, Direction) -> {ok, FdExport} = file:open("/sys/class/gpio/export", [write]), file:write(FdExport, integer_to_list(Pin)), file:close(FdExport), {ok, FdPinDir} = file:open("/sys/class/gpio/gpio" ++ integer_to_list(Pin) ++ "/direction", [write]), case Direction of in -> file:write(FdPinDir, "in");
end, file:close(FdPinDir), {ok, FdPinVal} = file:open("/sys/class/gpio/gpio" ++ integer_to_list(Pin) ++ "/value", [read, write]), FdPinVal.
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write(Fd, Val) -> file:position(Fd, 0), file:write(Fd, integer_to_list(Val)). read(Fd) -> file:position(Fd, 0), {ok, Val} = file:read(Fd, 1), Val. release(Pin) -> {ok, FdUnexport} = file:open("/sys/class/gpio/unexport", [write]), file:write(FdUnexport, integer_to_list(Pin)), file:close(FdUnexport).
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http://vimeo.com/40769788
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PidA Pin17 PidB PidC
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PidA Pin17 PidB PidC GPIO Proxy
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embedded design
– Access control/mutual exclusion
– Toggling rate, sequence detection, direction control, etc.
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– Application code becomes simpler – Concise and shorter modules – Testing becomes easier – Code re-use (potentially) increases
– Architecting fine grain systems is difficult
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Universal Peripheral/Component Modules
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Universal Peripheral/Component Modules
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Parallella:
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https://www.erlang-solutions.com/downloads/download-erlang-otp
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developing the next generation of concurrent and distributed Embedded Systems
– Embedded Linux Primer – Erlang/OTP 101 – Erlang Embedded Framework
Get in touch if you’re interested.
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The world is concurrent. Things in the world don't share data. Things communicate with messages. Things fail.
Co-inventor of Erlang
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