# 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:
* `packbeam` Generate AtomVM packbeam files from your `rebar3` project and its dependencies.
* `esp32_flash` Flash AtomVM packbeam files to ESP32 devices over a serial connection.
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`](https://hex.pm/packages/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`](https://github.com/atomvm/atomvm_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] [-s <start>]
-e, --external External AVM modules
-f, --force Force rebuild
-p, --prune Prune unreferenced BEAM files
-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
## 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:
* ATOMVM_REBAR3_PLUGIN_ESP32_FLASH_ESPTOOL
* ATOMVM_REBAR3_PLUGIN_ESP32_FLASH_CHIP
* ATOMVM_REBAR3_PLUGIN_ESP32_FLASH_PORT
* ATOMVM_REBAR3_PLUGIN_ESP32_FLASH_BAUD
* ATOMVM_REBAR3_PLUGIN_ESP32_FLASH_OFFSET
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.
## 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
