README.md

arduino_language_server

Necessary extra configuration

The Arduino Language Server does not come fully bootstrapped out of the box. In order for the language server to successfully start, you need to provide which FQBN (e.g. "arduino:avr:nano") it should start with.

This is done during server setup, and can be done by providing a custom cmd:

local MY_FQBN = "arduino:avr:nano"
lspconfig.arduino_language_server.setup {
    cmd = {
        "arduino-language-server",
        "-cli-config", "/path/to/arduino-cli.yaml",
        "-fqbn",
        MY_FQBN
    }
}

Dynamically changing FQBN per project

-- When the arduino server starts in these directories, use the provided FQBN.
-- Note that the server needs to start exactly in these directories.
-- This example would require some extra modification to support applying the FQBN on subdirectories!
local my_arduino_fqbn = {
    ["/home/h4ck3r/dev/arduino/blink"] = "arduino:avr:nano",
    ["/home/h4ck3r/dev/arduino/sensor"] = "arduino:mbed:nanorp2040connect",
}

local DEFAULT_FQBN = "arduino:avr:uno"

lspconfig.arduino_language_server.setup {
    on_new_config = function (config, root_dir)
        local fqbn = my_arduino_fqbn[root_dir]
        if not fqbn then
            vim.notify(("Could not find which FQBN to use in %q. Defaulting to %q."):format(root_dir, DEFAULT_FQBN))
            fqbn = DEFAULT_FQBN
        end
        config.cmd = {
            "arduino-language-server",
            "-cli-config", "/path/to/arduino-cli.yaml",
            "-fqbn",
            fqbn
        }
    end
}

FQBN

A FQBN, fully qualified board name, is used to distinguish between the various supported boards. Its format is defined as <package>:<architecture>:<board>, where

• <package> - vendor identifier; typically just arduino for Arduino boards
• <architecture> - microcontroller architecture; e.g., avr, megaavr, sam, etc.
• <board> - board name defined by the software; e.g., uno, uno2018, yun, etc.

To identify the available FQBNs for boards you currently have connected, you may use the arduino-cli command, like so:

$ arduino-cli board list
Port         Protocol Type              Board Name  FQBN            Core
/dev/ttyACM0 serial   Serial Port (USB) Arduino Uno arduino:avr:uno arduino:avr
                                                    ^^^^^^^^^^^^^^^