1.21 On the Ada language and embedded development
=================================================

2017-08-02

  I've been recently drawn to Ada (https://www.adacore.com/about-ada)
(once again).  Now, I'm a Lisper through and through and in a way Ada is
the exact opposite of Lisp, especially in terms of typing, but perhaps
because of that I find it quite interesting.  Showing the end result
right now, here is the canonical blinking LED done in Ada:

=###########****#%%%#%%#%%%%%%####%=.:*#############**####**********+.
-=======++==========-==-==-==------:...-:-:::::::::::::::::::::::::::.
---===========-==-=---=-::::::::::::--.::::::::::::::::::::::::::::::.
-+=++==-----------------------:--::-#%*:--:::::::::::::::::::::::::::.
-++++++=+=+==------------------::=-=**+:--:---:::::::::::::::::::::::.
-====-==----------------------+:.==+=--=:-----:::::::::::::::::::::::.
-=+*+++++===+=----------------=*--+#+-===::-:::::::::::::::::::::::.:.
--=+++=+++==+=---------------:=#----==***-.-:::::::::::::::::::::::.:.
-=++=+=======-=====------:----:.:=: --+#+=.::::::::::::::::::::::::.:.
--=+*++++++*+======--:::::-----.:=-.:==+*+:::::::::::::::::::::::::.:.
---=****++=+===-===-:::::------:.=-.:+-+++-.:::::::::::::::::::::::.:.
:++++*===---------::::::::::::-:.=----:----::::::::::::::::::::::::.:.
:==-======---------:::::::::::::-----::::::::::::::::::::::::::::::.:.
:----====--------::::::::::::::::::::::::::::::::::::::::::::::::::.:.
:----=--------:::::::::::::::::::::::::::::::::::::::::::::::::::::.:.
:-----------::::::::::::::::::::::::::::::::::::::::::.......:::::..:.
:------::::::::::::::::::::::::::::::::::::::::::::::::::---:::::.:.:.
::----===----===============++++++++++++++++++++======++++++=------:-.
::=+++===------------------------------:::::::::::::.:...............

Arduino blinking through Ada code

  Searching around I found the Make With Ada competition
(http://www.makewithada.org/), and I went looking for ways to use Ada
with what I had immediately available.  I found the AVR-Ada project
(https://sourceforge.net/p/avr-ada/wiki/Home/) which looked great.  The
build process depends on specific versions of the different components
(which is quite common), and I spent some time following the manual
build process... but then I remembered that I use Docker as a way to
encapsulate certain environments.

  Since I didn't found an existing AVR-Ada image I created one, built
on the shoulders of Tero Koskinen‘s Fedora 25 RPMs
(http://arduino.ada-language.com/author/tero-koskinen.html),and uploaded
them to the Docker hub (https://hub.docker.com/r/fsmunoz/avr-ada/).  The
goal is to reduce the “cost of entry” for using AVR-Ada.

1.21.1 Building it
------------------

As an example, building a typical “make the internal LED of the Arduino
blink” solution will be as simple as:

  • Downloading the docker image

    docker pull fsmunoz/avr-ada

  • Create the container with something like the following (I use alias
    for most docker containers and then just use them as commands in
    the terminal):

    alias avr-ada="docker run -it --rm \
     -v $HOME/src:/src:Z \
     --device /dev/ttyACM0 \
     --name avr-ada \
     --group-add dialout \
     fsmunoz/avr-ada"

  • Create an initial project; I would suggest Tero's blinking led
    repository.  To get an idea of what the code looks like, here it is
    (also, here's the gist in GitHub
    (https://gist.github.com/fsmunoz/5865663537966937540a8090b675bcc9#file-blink-adb):

    -- Blink the internal LED of an Arduino (and others) using AVR-Ada
    --
    -- Code by Tero Koskinen
    -- http://arduino.ada-language.com/blinking-led.html

    with AVR;
    with AVR.MCU;
    with AVR.Real_Time.Delays;

    use AVR;

    procedure Blink is
       Led_On : Boolean := False;
       LED_PIN : constant := 5;

    begin
       MCU.DDRB_Bits (LED_PIN) := DD_Output;
       loop
          Led_On := not Led_On;
          MCU.PORTB_Bits (LED_PIN) := Led_On;
          delay 8.0;
       end loop;
    end Blink;

  • In the docker image navigate to the source dir (which is why in the
    example above you can see I mapped ~/src to /src in the container).

  • Do a “make” and a “make upload”; something like this:

    $ make blink.prog
    avr-gnatmake -XMCU=atmega328p -p -Pbuild.gpr -XAVRADA_MAIN=blink
    avr-gnatmake: "/src/ada/arduino/blink/blink.elf" up to date.
    avrdude -p atmega328p -P /dev/ttyACM0 -c arduino -U flash:w:blink.hex

    avrdude: AVR device initialized and ready to accept instructions

    Reading | ################################################## | 100% 0.00s

    avrdude: Device signature = 0x1e950f (probably m328p)
    avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
     To disable this feature, specify the -D option.
    avrdude: erasing chip
    avrdude: reading input file "blink.hex"
    avrdude: input file blink.hex auto detected as Intel Hex
    avrdude: writing flash (1096 bytes):

    Writing | ################################################## | 100% 0.19s

    avrdude: 1096 bytes of flash written
    avrdude: verifying flash memory against blink.hex:
    avrdude: load data flash data from input file blink.hex:
    avrdude: input file blink.hex auto detected as Intel Hex
    avrdude: input file blink.hex contains 1096 bytes
    avrdude: reading on-chip flash data:

    Reading | ################################################## | 100% 0.15s

    avrdude: verifying ...
    avrdude: 1096 bytes of flash verified

    avrdude: safemode: Fuses OK (E:00, H:00, L:00)

    avrdude done. Thank you.

  • Relaxen und watchen das blinkenlichten.

  On a more general note I confess that I find the typical objections
to Ada tiresome, especially the “bondage and discipline language
designed by committee”.  I also read the Jargon File and I was raised in
that very same culture, but it comes a time when one needs to go a bit
deeper, and the “designed by committee” objection is more of an
ideological statement than a practical one.  Additionally, I have read
some comments on how AdaCore (the main company behind Ada technoloy, but
no the only one) is somehow "wrong" in supplying all the tools (GNAT)
but not providing an exception clause to the GPL. I must say that I find
this usage perfectly natural and to the spirit of the GPL: the exception
clause on GCC was always a tactical measure, not a strategic one, and
AdaCore is as far as I know working steadily on the GPL edition, and
this is actually the whole idea behind the GPL.

  This is a completely different topic but the “business friendly”
mantra that BSDers in general like to use is mostly the liberty for
companies to use code and then close it up and profit, and this is seen
as good - _but when a company opens up the code by using the GPL and
thus benefits users_ it is seen as "unfriendly".  As with most things an
analysis of good and bad is dependent on who has to gain -- cui bono?
This is perhaps worthy of a different post.

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