SkillsCast

G'Day, Nerves!

5th May 2021 in Online Event

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What is Nerves? What's the community like? How is it used?? These and more to be answered by this adventure into the world of functional embedded development using Elixir and the BEAM VM to create fault tolerant hardware systems...or blinking LED's...YMMV

Q&A

I show several links in my talk. Here they are in order so you don't have to manually search

* https://hexdocs.pm/nerves/getting-started.html
* https://github.com/jjcarstens/replex
* https://github.com/F5OEO/rpitx
* Erlang! The movie - https://www.youtube.com/watch?v=BXmOlCy0oBM
* https://erlang.org/doc/man/heart.html
* https://github.com/nerves-project/nervesheart
* https://embedded-elixir.com/post/2018-12-10-heart/
* Nerves of Steel - https://www.youtube.com/watch?v=tuY2IxAfe-I
* https://github.com/nerves-project/nervesexamples
* https://elixir-circuits.github.io
* https://github.com/elixir-circuits/circuitsquickstart
* https://github.com/fhunleth/nerveslivebook
* https://github.com/drizzle-org/drizzle
* https://github.com/nerves-keyboard
* https://farm.bot
* https://smartrent.com
* #nerves channel in Elixir slack - https://elixir-lang.slack.com/archives/C0AB4A879
* Nerves Forum - https://elixirforum.com/c/nerves-forum/74
* https://nerves.group
* https://github.com/nerves-project

Question: Would Nerves suit hard realtime systems?

Answer: Well, this might be a loaded question of personal preference. I think you could definitely start with it and get very far, but it depends on how strictly you need “hard” real time as Nerves is prob closer to being soft real time.

Question: I think Erlang itself is meant for soft realtime systems

Answer: Yes. The GRiSP project is another embedded erlang setup targeted for “bare-metal erlang” and hard real-time event handling which might be worth a look as well:

https://www.grisp.org

The difference being GRiSP is custom designed hardware and erlang VM vs Nerves which relies on Linux kernel + buildroot. But at the end of the day, Erlang is more for the soft real time

O! And, what we do for this requirement is typically do hard real time on a microcontroller that interfaces with Nerves, and then Nerves does the control and command in Elixir

Question: I'm a realtime systems noob. What's "hard" realtime? Very small slice guarantee? Very low probability of missing a slice?

Answer: It's all about guarantees down to the processor deadlines. It basically means you cannot miss any computational deadline when chomping the bits which gets problematic on processor load, because timings may fail where “soft real time” can handle those missed deadlines with reschedules and eventually hit the mark. But we’re talking like imperceptible deadlines that only become noticeably missed accrued over time.

Question: Has there been any work with Nerves and network booting?

Answer: I think you might need to elaborate your question for me? Just to boot an image remotely on the network? Or maybe..whats your direct goal here?

Question: Right to boot an image from the network instead of using an sd card. I was thinking for the ability to have more than 1 fallback and less upstream internet usage if a firmware can be downloaded once and then shared on a local network.

Answer: There is not work I know of for network booting. for rpi, there has been work to utilize initramfs and some other intermediate files, but thats an interesting idea to be able to netboot. Though the main use-case I can think of would be to obtain the first firmware, such as provisioning new hardware.

I’m going to have to look at this more. There is also the option to use Erlang to connect local devices in distribution and pass the new firmware there instead

We have a lot of devices on cellular and reducing network traffic is a huge deal. The route we’ve been going is for delta-updates and only sending the change bits of the firmware to the device. Thats currently supported be default in the official systems and https://nerves-hub.org supports delivering those firmware updates.

Question: I'm going to have to get into this. I'm also a qualified security technician (alarms/ CCTV/ access control/ home automation). Are there implementations on commercial grade hardware?

Answer: What you’d prob want to look at are what “systems” have been ported so far. We develop a lot of in house hardware for this using Octavo and iMX6uLL chipsets which I see used a lot more https://hex.pm/packages?search=nervessystem&sort=recentdownloads

And there are other places using it commercially, like https://farm.bot . I believe there is also a startup to use it with grid system monitoring

Basically, you would see what processor the target hardware is using, see if there is a nervessystem* port for it, or port yourself

O! And we also use it with access control systems with the iMX6uLL chip, but has been a pretty custom setup

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