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Introduction to Embedded Systems Programming (Ada)

135 points by gusthoff 4y ago

synack 4y ago
AdaCore's docs are fantastic for understanding why things are done the way they are. However, when I'm learning a new platform or language I prefer to see a lot of practical examples first. That's what I tried to do with my "Ada on the Raspberry Pi Pico" project: https://pico-doc.synack.me/ https://pico-doc.synack.me/
- touisteur 4y ago
  Rosetta code is also a great help for classic stuff (not specifically embedded I mean).
- bmitc 4y ago
  This is really cool. Thanks for sharing this. Is this a workable solution for the Raspberry Pi or is it more of a proof of concept? I need to learn Ada, but I'm really not a fan of C/C++ or Python, so I haven't gotten to join in on the fun of the Pico, yet.
  - synack 4y ago
    It's more than a proof of concept; there are lots of examples, unit tests, and the linked documentation. Pico Keys (https://www.tindie.com/products/fabien-c/pico-keys/ https://www.tindie.com/products/fabien-c/pico-keys/) is a good example of a complex project built with rp2040_hal. Note that this library is specific to the RP2040, not the larger Raspberry Pi boards. Some Ada drivers for those exist, but are not as well documented. I also gave a short talk about some of the challenges I encountered earlier this year: https://youtu.be/Pwd9Q5ELAGM https://youtu.be/Pwd9Q5ELAGM
bmitc 4y ago
This seems like a great tutorial for both Ada and embedded systems in general. I'm definitely going to have to check this out more. Can someone speak, at a high-level, on how Ada manages memory? I'm gonna read the docs, but if anyone has a good explanation here, that would be appreciated! In general, I'm interested in learning more about embedded languages that are not C/C++ or Rust. To give some context, my dream embedded language is one like F# or OCaml that can be embedded (i.e., has manual memory management or some other solution).
- theonething 4y ago
  If you haven't already, the Nerves Project which is an embedded systems/IoT platform based on Elixir, might interest you. https://www.nerves-project.org/ https://www.nerves-project.org/
  - bmitc 4y ago
    Yep! I love Elixir and am definitely aware of it. I haven't used Nerves proper yet, just some of the libraries that it's associated with, but I'd like to at one point. However, it is limited to soft real-time systems.
- csb6 4y ago
  Ada’s memory management is a mix of memory pools, RAII, and manual memory management. It often isn’t necessary to explicitly use pointers to dynamically allocated memory. For example, Ada lets you return an array of unknown size by value from a function. These unconstrained objects are stored on what is called a “secondary stack”, which is basically a special allocation pool for holding these objects managed by the language runtime. When you do use pointers, the compiler is very strict to try and avoid dangling pointers. You can also create custom pointer types and assign them to memory pools, so dynamic allocations of that pointer type get made in the pool (and not in the normal heap). You can also use manual memory management (using the `new` keyword and the `Unchecked_Deallocation` function similar to malloc() and free()). There is also a finalizer class you can inherit from that adds a destructor to record types, so you can use RAII, too.
- elcritch 4y ago
  Checkout Nim! I've used it to great effect for embedded programming. It has memory management system based on non-atomic reference counting (arc) so its fast and deterministic. It has optional cycle collection too (orc). Its easy to mixin manual memory as well. I used F# a bit and learned a lot from it, and the same with Elixir and Nerves. Nim is procedural but it has an "enlightened procedural" take that feels like functional programming in some ways. Partly thats due to the very powerful type system - for example Nim lets you define custom distinct (not aliased) number types just like F#. Nim also inherits a fair bit from Pascal and so shares points with Ada like ints with custom ranges. Theres some rough points, but largely its made me enjoy programming again. The esp32 is a good intro route since they're easy to setup. I wrote a wrapper for esp-idf which is used in production in at least two embedded shops: https://github.com/elcritch/nesper https://github.com/elcritch/nesper (its stable but I haven't had time to update docs for a ehile) You can run it on Arduinos as well. Theres a pure Nim setup called Ratel and a rp2040 wrapper too. :)
gaudat 4y ago
Seems like an interesting language to learn. But I am getting PTSD from writing VHDL which is based on Ada. Is pure Ada's syntax as inconsistent as VHDL's?
- timbit42 4y ago
  On the left side of the page, click "Introduction to Ada" and then "Imperative Language" for some syntax.
inamberclad 4y ago
Ada is great, I just want to understand how streams work! I can't find good examples or explanations.
- micronian2 4y ago
  By chance have you tried reading the Ada wikibooks page? https://en.wikibooks.org/wiki/Ada_Programming/Libraries/Ada.Streams https://en.wikibooks.org/wiki/Ada_Programming/Libraries/Ada....

135 points by gusthoff 4y ago

AdaCore's docs are fantastic for understanding why things are done the way they are. However, when I'm learning a new platform or language I prefer to see a lot of practical examples first. That's what I tried to do with my "Ada on the Raspberry Pi Pico" project: https://pico-doc.synack.me/ https://pico-doc.synack.me/

touisteur 4y ago
Rosetta code is also a great help for classic stuff (not specifically embedded I mean).
bmitc 4y ago
This is really cool. Thanks for sharing this. Is this a workable solution for the Raspberry Pi or is it more of a proof of concept? I need to learn Ada, but I'm really not a fan of C/C++ or Python, so I haven't gotten to join in on the fun of the Pico, yet.
- synack 4y ago
  It's more than a proof of concept; there are lots of examples, unit tests, and the linked documentation. Pico Keys (https://www.tindie.com/products/fabien-c/pico-keys/ https://www.tindie.com/products/fabien-c/pico-keys/) is a good example of a complex project built with rp2040_hal. Note that this library is specific to the RP2040, not the larger Raspberry Pi boards. Some Ada drivers for those exist, but are not as well documented. I also gave a short talk about some of the challenges I encountered earlier this year: https://youtu.be/Pwd9Q5ELAGM https://youtu.be/Pwd9Q5ELAGM

bmitc 4y ago

This seems like a great tutorial for both Ada and embedded systems in general. I'm definitely going to have to check this out more. Can someone speak, at a high-level, on how Ada manages memory? I'm gonna read the docs, but if anyone has a good explanation here, that would be appreciated! In general, I'm interested in learning more about embedded languages that are not C/C++ or Rust. To give some context, my dream embedded language is one like F# or OCaml that can be embedded (i.e., has manual memory management or some other solution).

theonething 4y ago
If you haven't already, the Nerves Project which is an embedded systems/IoT platform based on Elixir, might interest you. https://www.nerves-project.org/ https://www.nerves-project.org/
- bmitc 4y ago
  Yep! I love Elixir and am definitely aware of it. I haven't used Nerves proper yet, just some of the libraries that it's associated with, but I'd like to at one point. However, it is limited to soft real-time systems.
csb6 4y ago
Ada’s memory management is a mix of memory pools, RAII, and manual memory management. It often isn’t necessary to explicitly use pointers to dynamically allocated memory. For example, Ada lets you return an array of unknown size by value from a function. These unconstrained objects are stored on what is called a “secondary stack”, which is basically a special allocation pool for holding these objects managed by the language runtime. When you do use pointers, the compiler is very strict to try and avoid dangling pointers. You can also create custom pointer types and assign them to memory pools, so dynamic allocations of that pointer type get made in the pool (and not in the normal heap). You can also use manual memory management (using the `new` keyword and the `Unchecked_Deallocation` function similar to malloc() and free()). There is also a finalizer class you can inherit from that adds a destructor to record types, so you can use RAII, too.
elcritch 4y ago
Checkout Nim! I've used it to great effect for embedded programming. It has memory management system based on non-atomic reference counting (arc) so its fast and deterministic. It has optional cycle collection too (orc). Its easy to mixin manual memory as well. I used F# a bit and learned a lot from it, and the same with Elixir and Nerves. Nim is procedural but it has an "enlightened procedural" take that feels like functional programming in some ways. Partly thats due to the very powerful type system - for example Nim lets you define custom distinct (not aliased) number types just like F#. Nim also inherits a fair bit from Pascal and so shares points with Ada like ints with custom ranges. Theres some rough points, but largely its made me enjoy programming again. The esp32 is a good intro route since they're easy to setup. I wrote a wrapper for esp-idf which is used in production in at least two embedded shops: https://github.com/elcritch/nesper https://github.com/elcritch/nesper (its stable but I haven't had time to update docs for a ehile) You can run it on Arduinos as well. Theres a pure Nim setup called Ratel and a rp2040 wrapper too. :)

gaudat 4y ago

Seems like an interesting language to learn. But I am getting PTSD from writing VHDL which is based on Ada. Is pure Ada's syntax as inconsistent as VHDL's?

timbit42 4y ago
On the left side of the page, click "Introduction to Ada" and then "Imperative Language" for some syntax.

inamberclad 4y ago

Ada is great, I just want to understand how streams work! I can't find good examples or explanations.

micronian2 4y ago
By chance have you tried reading the Ada wikibooks page? https://en.wikibooks.org/wiki/Ada_Programming/Libraries/Ada.Streams https://en.wikibooks.org/wiki/Ada_Programming/Libraries/Ada....