atomvm_rebar3_plugin

A rebar3 plugin for simplifying development of Erlang applications targeted for the <a href="http://github.com/bettio/AtomVM">AtomVM</a> Erlang abstract machine.

This rebar3 plugin provides the following targets:

The atomvm_rebar3_plugin plugin makes use of the <a href="https://github.com/fadushin/packbeam">packbeam</a> tool, internally.

Getting Started

Create a rebar3 project (app or lib), e.g.,

shell$ rebar3 new lib mylib
===> Writing mylib/src/mylib.erl
===> Writing mylib/src/mylib.app.src
===> Writing mylib/rebar.config
===> Writing mylib/.gitignore
===> Writing mylib/LICENSE
===> Writing mylib/README.md

Add the plugin to the rebar config:

{plugins, [
    ...
    atomvm_rebar3_plugin
    ...
]}.

Note. Check the latest version in the atomvm_rebar3_plugin Hex repository.

Create a file called main.erl in the src directory with the contents:

-module(main).
-export([start/0]).

start() ->
    ok.

Use the packbeam target to create an AVM file:

shell$ rebar3 packbeam
===> Analyzing applications...
===> Compiling atomvm_rebar3_plugin
===> Compiling packbeam
...
===> Verifying dependencies...
===> Analyzing applications...
===> Compiling mylib
===> AVM file written to : mylib.avm

The generated AVM file can be found in _build/default/lib/mylib.avm.

You can use the packbeam tool to list the contents of this generated file:

shell$ packbeam list _build/default/lib/mylib.avm
main.beam * [320]
mylib.beam [228]
mylib/priv/application.bin [228]

The packbeam target

The packbeam target is used to generated an AtomVM packbeam (.avm) file.

shell$ rebar3 help packbeam
...
A rebar plugin to create packbeam files
Usage: rebar3 packbeam [-e] [-f] [-p] [-i] [-r] [-s <start>]

-e, --external       External AVM modules
-f, --force          Force rebuild
-p, --prune          Prune unreferenced BEAM files
-i, --include_lines  Include line information in generated AVM files
                     (deprecated)
-r, --remove_lines   Remove line information from generated AVM files
                     (off by default)
-s, --start          Start module

E.g.,

shell$ rebar3 packbeam
===> Compiling packbeam
===> Compiling atomvm_rebar3_plugin
===> Compiling packbeam
===> Compiling atomvm_rebar3_plugin
===> Verifying dependencies...
===> Compiling mylib
===> AVM file written to : mylib.avm

When using this target, an AVM file with the project name will be created in _build/<profile>/lib/, .e.g.,

shell$ ls -l _build/default/lib/mylib.avm
-rw-rw-r--  1 frege  wheel  8780 May 15 1895 22:03 _build/default/lib/mylib.avm

If your project has any erlang dependencies, the packbeam target will include any BEAM files or priv files from the dependent projects in the final AVM file.

If your project (or any of its dependencies) has multiple modules that export a start/0 entry-point function, you can specify which module to use as the entry-point for your application via the --start (or -s) option:

shell$ rebar3 packbeam --start my_start_module
...

Using this option will ensure that the generated AVM file with use my_start_module to start the application.

You may use the --prune option (or -p) to prune unnecessary beam files when creating AVM files. Pruning unnecessary files can make your AVM files smaller, leading to faster development cycles and more free space on flash media. Pruning is not enabled by default. Note that if you use the prune option, your project (or at least one of its dependencies) must have a start/0 entry-point. Otherwise, you should treat your project as a library, suitable for inclusion in a different AtomVM project.

The packbeam target will use timestamps to determine whether a rebuild is necessary. However, timestamps may not be enough to trigger a rebuild, for example, if a dependency was added or removed. You can force a rebuild of AVM file by adding the --force flag (or -f), with no arguments. All AVM files, including AVM files for dependencies, will be rebuilt regardless of timestamps.

The packbeam target depends on the compile target, so any changes to modules in the project will automatically get rebuilt when running the packbeam target.

Building OTP Applications

You can use the packbeam target to build AtomVM applications that implements the OTP application behavior, and the atomvm_rebar3_plugin will create an AVM file that contains boot information to start your application automatically when AtomVM starts.

For example, a module that implements the OTP application behavior might look as follows:

%% erlang
-module(myapp_app).

-export([start/2, stop/1]).

start(_Type, Args) ->
    io:format("Starting myapp_app ...~n"),
    myapp_sup:start(Args).

stop(_State) ->
    myapp_sup:stop_children().

(assume myapp_sup is also a part of your OTP application).

And the application configuration file (e.g., myapp.app.src) should include the application mdoule (myapp_app) under it's mod entry:

{
    application, myapp, [
        {description, "My AtomVM application"},
        {vsn, "0.1.0"},
        {registered, []},
        {applications, [
            kernel,
            stdlib
        ]},
        {env,[]},
        {mod, {myapp_app, []}},
        {modules, []},
        {licenses, ["Apache 2.0"]},
        {links, []}
    ]
}.

If you specify init as the start module, then an AVM file will be created:

shell$ rebar3 packbeam -p -s init
===> Analyzing applications...
===> Compiling atomvm_rebar3_plugin
===> Compiling packbeam
...
===> Analyzing applications...
===> Compiling myapp
===> AVM file written to : myapp.avm

This AVM file will contain the init.beam module, along with a boot script (init/priv/start.boot), which will be used by the init.beam module to start your application automatically.

For example:

shell$ packbeam list _build/default/lib/myapp.avm
init.beam * [1428]
myapp_worker.beam [596]
myapp_sup.beam [572]
myapp_app.beam [416]
myapp/priv/application.bin [288]
init/priv/start.boot [56]
myapp/priv/example.txt [24]

Running this AVM file will boot the myapp application automatically, without having to write an entrypoint module.

External Dependencies

If you already have AVM modules are not available via rebar3, you can direct the packbeam target to these AVM files via the -e (or --external) flag, e.g.,

shell$ rebar3 packbeam -e <path-to-avm-1> -e <path-to-avm-2> ...
===> Fetching packbeam
===> Compiling packbeam
===> Compiling atomvm_rebar3_plugin
===> Compiling atomvm_rebar3_plugin
===> Verifying dependencies...
===> Compiling mylib
===> AVM file written to : mylib.avm

Line Number Information

By default, running the packbeam target will generate line number information in packbeam files. This information is used at runtime to generate stracktrace information about the file location of frames in a stacktrace. This information can be essential for debugging, but for finalized projects, some users may want to strip line information from applications, in order to save on memory at runtime and space on flash.

You can use the -r or --remove_lines flags to packbeam, to remove line information from packbeam files.

The esp32-flash target

You may use the esp32_flash target to flash the generated AtomVM packbeam application to the flash storage on an ESP32 device connected over a serial connection.

shell$ rebar3 help esp32_flash
...
A rebar plugin to flash packbeam to ESP32 devices
Usage: rebar3 esp32_flash [-e] [-p] [-b] [-o]

-e, --esptool  Path to esptool.py
-c, --chip     ESP chip (default esp32)
-p, --port     Device port (default /dev/ttyUSB0)
-b, --baud     Baud rate (default 115200)
-o, --offset   Offset (default 0x210000)

The esp32_flash will use the esptool.py command to flash the ESP32 device. This tool is available via the <a href="https://docs.espressif.com/projects/esp-idf/en/latest/esp32/">IDF SDK</a>, or directly via <a href="https://github.com/espressif/esptool">github</a>. The esptool.py command is also avalable via many package managers (e.g., MacOS Homebrew).

By default, the esp32_flash target will assume the esptool.py command is available on the user's executable path. Alternatively, you may specify the full path to the esptool.py command via the -e (or --esptool) option

By default, the esp32_flash target will write to port /dev/ttyUSB0 at a baud rate of 115200. You may control the port and baud settings for connecting to your ESP device via the -port and -baud options to the esp32_flash target, e.g.,

shell$ rebar3 esp32_flash --port /dev/tty.SLAB_USBtoUART --baud 921600
===> Compiling packbeam
===> Compiling atomvm_rebar3_plugin
===> Compiling packbeam
===> Compiling atomvm_rebar3_plugin
===> Verifying dependencies...
===> Compiling mylib
===> esptool.py --chip esp32 --port /dev/tty.SLAB_USBtoUART --baud 921600 --before default_reset --after hard_reset write_flash -u --flash_mode dio --flash_freq 40m --flash_size detect 0x110000 /home/frege/mylib/_build/default/lib/mylib.avm
esptool.py v2.1
Connecting........_
Chip is ESP32D0WDQ6 (revision 1)
Uploading stub...
Running stub...
Stub running...
Changing baud rate to 921600
Changed.
Configuring flash size...
Auto-detected Flash size: 4MB
Wrote 16384 bytes at 0x00110000 in 0.2 seconds (615.0 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting...

Alternatively, the following environment variables may be used to control the above settings:

Any setting specified on the command line take precedence over environment variable settings, which in turn take precedence over the default values specified above.

The esp32_flash target depends on the packbeam target, so any changes to modules in the project will get rebuilt before being flashed to the device.

The stm32-flash target

Preparing an application for flashing

The stm32 builds of AtomVM do not include a library partition and atomvmlib.avm is not flashed to the device. Instead the application should be compiled and packed along with atomvmlib.avm before flashing, for example:

shell$ rebar3 packbeam -p -e /path/to/atomvmlib.avm

Consult rebar3 help packbeam for other options.

Flashing an application to a stm32 device

You may use the stm32_flash target to flash the generated AtomVM packbeam application to the flash storage on an STM32 device connected to an st-link.

shell$ rebar3 help stm32_flash
A rebar plugin to flash packbeam to STM32 devices
Usage: rebar3 stm32_flash [-s] [-o]

-s, --stflash  Path to st-flash
-o, --offset   Offset (default 0x8080000)

The stm32_flash will use the st-flash tool from the open source (bsd-3 liscensed) stlink suite of stm32 utilites to flash the STM32 device. This tool is available on github, and in many package managers.

By default, the stm32_flash target will assume the st-flash command is available on the user's executable path. Alternatively, you may specify the full path to the st-flash command via the -s (or --stflash) option

shell$ rebar3 stm32_flash --stflash /usr/bin/st-flash --offset 0x8080000
===> Verifying dependencies...
===> Analyzing applications...
===> Compiling stm32_hello
===> st-flash --reset write /home/atomvm/AtomVM/stm32_hello/_build/default/lib/stm32_hello.avm 0x8080000

st-flash 1.7.0
2023-07-09T21:42:26 INFO common.c: F42x/F43x: 256 KiB SRAM, 2048 KiB flash in at least 16 KiB pages.
file /home/atomvm/AtomVM/stm32_hello/_build/default/lib/stm32_hello.avm md5 checksum: 5747b8eab41a3696097eb386c785e, stlink checksum: 0x00154e50
2023-07-09T21:42:26 INFO common.c: Attempting to write 29304 (0x7278) bytes to stm32 address: 134742016 (0x8080000)
EraseFlash - Sector:0x8 Size:0x20000 2023-07-09T21:42:28 INFO common.c: Flash page at addr: 0x08080000 erased
2023-07-09T21:42:28 INFO common.c: Finished erasing 1 pages of 131072 (0x20000) bytes
2023-07-09T21:42:28 INFO common.c: Starting Flash write for F2/F4/F7/L4
2023-07-09T21:42:28 INFO flash_loader.c: Successfully loaded flash loader in sram
2023-07-09T21:42:28 INFO flash_loader.c: Clear DFSR
2023-07-09T21:42:28 INFO common.c: enabling 32-bit flash writes
2023-07-09T21:42:29 INFO common.c: Starting verification of write complete
2023-07-09T21:42:29 INFO common.c: Flash written and verified! jolly good!

Alternatively, the following environment variables may be used to control the above settings:

Any setting specified on the command line take precedence over environment variable settings, which in turn take precedence over the default values specified above.

AtomVM App Template

The atomvm_rebar3_plugin contains template definitions for generating skeletal rebar3 projects.

The best way to make use of this template is to include the atomvm_rebar3_plugin in your ~/.config/rebar3/rebar.config file, e.g.,

%% TODO set a tag
{plugins, [
    atomvm_rebar3_plugin
]}.

You can then generate a minimal AtomVM application as follows:

shell$ rebar3 new atomvm_app myapp
===> Writing myapp/LICENSE
===> Writing myapp/rebar.config
===> Writing myapp/src/myapp.erl
===> Writing myapp/src/myapp.app.src
===> Writing myapp/README.md

This target will create a simple rebar3 project with a minimal AtomVM application in the myapp directory.

Change to the myapp directory and issue the packbeam target to the rebar3 command:

shell$ cd myapp
shell$ rebar3 packbeam
===> Fetching atomvm_rebar3_plugin
===> Fetching packbeam
===> Compiling packbeam
===> Compiling atomvm_rebar3_plugin
===> Verifying dependencies...
===> Compiling myapp
===> AVM file written to : myapp.avm

An AtomVM AVM file is created in the _build/default/lib directory:

shell$ ls -l _build/default/lib/myapp.avm
-rw-rw-r--  1 frege  wheel  328 Jan 1 1970 00:01 _build/default/lib/myapp.avm