Creating Your First GRiSP Application

Before proceeding with this guide, make sure you have set up your development environment according to Setting Up a Development Environment.

Prepare your SD card

⚠️ Please read this FAQ before proceding: Which file system should the SD card be formatted with?

Creating a New Project

1. First, we create a new project using the GRiSP application template. We will use the name robot for the project in this tutorial. The destination path /tmp/sd_card should be replaced with where your SD-card is mounted in your operating system. For a FAT32 formatted SD-card with the name GRISP the locations will most likely be:

   • /Volumes/GRISP on macOS
   • /media/GRISP on Linux is common, but it can vary. Check the details for your distribution.

   It also works fine with using /tmp/sd_card which lets you to test the deployment locally and allows you to copy the files to an SD-card at a later time.

   $ cd ~/GRiSP
   $ rebar3 new grispapp name=robot dest=/tmp/sd_card
   ===> Writing robot/src/robot.erl
   ===> Writing robot/src/robot_sup.erl
   ===> Writing robot/src/robot.app.src
   ===> Writing robot/rebar.config
   ===> Writing robot/.gitignore
   ===> Writing robot/LICENSE
   ===> Writing robot/README.md
   $ cd robot
   

This is all that is needed to start development and later deploy the application to the GRiSP board itself.

Adding Code

Let us create an application that uses the color LEDs already present on the board.

1. Edit src/robot.erl to contain the following:

   % @doc robot public API.
   % @end
   -module(robot).
   
   -behavior(application).
   
   % Callbacks
   -export([start/2]).
   -export([stop/1]).
   
   %--- Callbacks -----------------------------------------------------------------
   
   start(_Type, _Args) ->
       {ok, Supervisor} = robot_sup:start_link(),
       LEDs = [1, 2],
       [grisp_led:flash(L, red, 500) || L <- LEDs],
       timer:sleep(5000),
       grisp_led:off(2),
       Random = fun() ->
           {rand:uniform(2) - 1, rand:uniform(2) -1, rand:uniform(2) - 1}
       end,
       grisp_led:pattern(1, [{100, Random}]),
       {ok, Supervisor}.
   
   stop(_State) -> ok.

   This will flash both LED red for 5 seconds, then switch to a randomly generated pattern on the first LED.

2. Make sure your changes compile without issues locally:

   $ rebar3 compile
   ===> Verifying dependencies...
   ===> Compiling robot
   $
   

Next Step

Continue with the guide Deploying a GRiSP Application.