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ArduinoStreamCommander

The ArduinoStreamCommander is a library for interacting with an Arduino over any Stream-based interface via commands, as long as the member functions setTimeout, available, println, readString, flush are implemented accordingly. Those interfaces include Serial (for which this library was initially meant for), SoftwareSerial, Wire and Ethernet.

The target was a very lightweight and convenient library, which allows to easily add new commands and send status updates automatically in case the data changed.

Features:

  • Execute commands on the device (e.g. to get or set different values of the device).
    • Add custom commands with callback functions.
    • Use a set of basic standard commands.
  • Send different kind of messages with a simple and lightweight message format.
    • Send status updates of the device (e.g. for pushing new sensor values via Serial Interface).
    • Send arbitrary types of messages.
  • Get/Set an ID from and to the EEPROM (If the target board has one available).

Folder structure

  • src contains the source code.
  • examples contains an example sketch.

Installing and using ArduinoStreamCommander with the Arduino IDE

  • Before usage, installing ArduinoStreamCommander-MessageTypes is required. This Lib just contains standard message types, but can be easily extended and customised if required.
  • To install the library either clone and ZIP the folder, or download one of the releases. After that follow the instructions here.
  • In order to use ArduinoStreamCommander, <StreamCommander.hpp> needs to be included.

Usage

For more detailed explainations on the particular functions/functionalities, please reference to the comments in the source code. Also, there's an example (examples/test/test.ino) which showcases the core functionalities of the StreamCommander.

Basic usage

  1. Instantiate a new ArduinoStreamCommander-Object: StreamCommander commander = StreamCommander();.
    The StreamCommander will be initialised with the standard Serial-Object by default.
    1. Optionally, instantiate the StreamCommander with an alternative Stream-based interface:
      StreamCommander commander = StreamCommander( &Serial1 );
  2. Initialise the Stream-interface, e.g.: Serial.begin( 9600 );
  3. Initialise the StreamCommander: commander.init();. (Optionally with arguments, see source code for more information.)
    1. Call further optional functions while setting up.
  4. Add custom commands with a name and a matching callback function, e.g.:
    commander.addCommand( "test", testCallback );
    1. The callback function has to follow following typedef:
      typedef void (*CommandCallbackFunction)( String arguments , StreamCommander * instance ).
  5. Optionally, set a default callback function, e.g.:
    commander.setDefaultCallback( defaultCallback );
    1. The callback function has to follow following typedef:
      typedef void (*DefaultCallbackFunction)( String command , String arguments , StreamCommander * instance )
  6. Call commander.fetchCommand(); in every loop(). This function catches incoming commands. If the command has been registered and found, the according callback will be called, and (optional) arguments will be parsed and passed to the according callback function. If the command has not been registered, the default callback will be called.
    1. This function can also be called after an hardware interrupt.
    2. Carriage return ("\r"), Newline ("\n") or Carriage return + Newline ("\r\n") do each signalise the end of a command.
  7. Send status updates with updateStatus-function.
    1. If the status has changed since the last update, a new status message will automatically be sent.
    2. If the device is not activated, possible status updates won't be sent out. They can still be queried manually with the status-command.
  8. In case you need the device to have an ID (for example if you need to adress multiple devices separately), set an id with the setid-command the first time you boot the device. If an EEPROM is available on the board:
    1. The ID will be persisted in the EEPROM of the device, and will automatically be loaded on every initialisation of the StreamCommander. No need to hardcode this.
    2. The ID will only be updated in the EEPROM if it really changes, which extends the lifespan of the EEPROM.

Arguments

A command can be followed by arguments. Those arguments are separated from the rest of the command by the first occurence of the command delimiter (a blank space by default). The delimiter can be changed with the function commander.setCommandDelimiter( char delimiter ); or in the init-function. The arguments are parsed as a single string, which can then be processed arbitrarily.

Example:

  • Command with arguments: test 1 2 3
  • Command: test
  • Arguments: 1 2 3

Defining Command-Callbacks

As stated above, a callback for commands follows the CommandCallbackFunction-typedef:
typedef void (*CommandCallbackFunction)( String arguments , StreamCommander * instance )
It has two parameters: a string of arguments, and a pointer to the instance of the StreamCommander calling the callback.

The latter parameter is especially there, in case multiple instances of stream commander are running (for example if we have multiple serial ports connected), in order to distinguish which instance called the callback.

If arguments have been passed with the command, the arguments are parsed and passed as a single string.

Example for turning the built in LED on and off:

commander.addCommand( "led", cmdLed );
...
void cmdLed( String arguments, StreamCommander * instance )
{
    arguments.trim();
    
    if ( arguments.equals( "on" ) )
    {
        digitalWrite( LED_BUILTIN, HIGH );
    }
    else if ( arguments.equals( "off" ) )
    {
        digitalWrite( LED_BUILTIN, LOW );
    }
}

Defining the Default-Callbacks

This function gets called if an unknown/unregistered command has been delivered to the StreamCommander. As stated above, the default callback follows the DefaultCallbackFunction-typedef:
typedef void (*DefaultCallbackFunction)( String command , String arguments , StreamCommander * instance )

In addition to the CommandCallbackFunction it has the parameter command which contains the name of the command that has been tried to be invoked.

Example:

commander.setDefaultCallback( cmdDefault );
...
void cmdDefault( String command, String arguments, StreamCommander * instance )
{
    instance->sendResponse( "Command \"" + command + "\" with arguments \"" + arguments + "\" not registered." );
}

Standard Commands

The StreamCommander has several standard commands which implement basic functionalities. Adding those commands can be surpressed by specifing this when calling the init-function.

Command Purpose Arguments
activate Activates the automatic publishing of new status-messages
deactivate Deactivates the automatic publishing of new status-messages
isactive Returns whether the device is set to active or not
setecho Sets the echoing of incoming commands on or off on / off
setid Sets the ID of the device <id>
getid Returns the ID of the device
ping Returns a ping response message (usually a "ping:reply" message)
getstatus Returns the current status of the device
commands Returns all registered commands of the device

Message format

To make the communication more easy and consistent, a simple message format has been defined, which is used by the ArduinoStreamCommander.
The definition can be found here: SerialMessageFormat

Standard Message Types

The StreamCommander uses several standard message types, which are defined in ArduinoStreamCommander-MessageTypes.

Type Purpose
response Return responses after a command has been executed
info Inform about something like an internal event (e.g. for logging-purposes)
error Inform about an error/problem which occured during the runtime
ping Contains a ping response message (usually containts "reply")
status Send the current/most recent status of the device (Especially used for status updates)
id Contains the id of the device
active Contains whether the device is set to active or not
echo Contains an echo of the last input received
commands Contains a list of all registered commands of a Device
command Contains a command to be passed to an Arduino