Arduilink

A very simple system of communication between Arduino and Raspberry using the serial to collect data from several sensors.

Example

// Required library
#include <Arduilink.h>

// Unique identifier of the node
#define NODE_ID 0

// Create the link
Arduilink link = Arduilink(NODE_ID);

// Setup function
void setup()
{
	// Declare several sensors
	link.addSensor(1, S_INFO, "Temperature sensor (DHT)", "celcius degree");
	link.addSensor(2, S_INFO, "Humidity sensor (DHT)", "percent");
	// Start serial link
	Serial.begin(9600);
	link.init();
}

// Loop function
void loop()
{
	link.setValue(1, mySensor.getTemperature());
	link.setValue(2, mySensor.getHumidity());
	sleep(5000);
}

// Serial events
void serialEvent()
{
  lnk.handleInput();
}

Once the Arduino is connected, the python service can be started . This server will connect permanently to the serial link, to be ready to read and write information to the Arduino. After starting the server, the client enables notably to gather the value of a sensor.

$ sudo chmod 777 /dev/ttyUSB0
$ sudo ./arduilink_server.py --file /dev/ttyUSB0 --rate 9600 --port 900 &
Socket: listening on port 900 ...
Serial: connected on /dev/ttyUSB0 (9600)
Serial: device is ready
$ ./arduilink_client.py --port 900 --get 2
35.05

---

Serial Protocol

The serial protocol used between the Gateway and the Controller is a simple semicolon separated list of values.

When you just get connected to serial link, the arduino will send a welcome message:

#####100;node-id;protocol-version\n

Then, the arduino can send a description of all connected sensors:

#####300;node-id;sensor-id;sensor-flags;sensor-unit;sensor-verbose-attribute;sensor-name\n

Each time a sensor has a new value, the following is sent:

#####200;node-id;sensor-id;data-value\n

Sending commands to arduino

Ask the arduino to present all his sensors:

#####PRESENT;node-id\n

Ask a description of a given sensor:

#####INFO;node-id;sensor-id\n

Gather the value of a given sensor:

#####GET;node-id;sensor-id\n

Change an attribute of a given sensor:

#####SET;node-id;sensor-id;attribute-name;ack;attribute-value\n

The arduino can answer with the following codes. If a SET command is succesfull the response will be:

#####201;node-id;sensor-id;attribute;new-attribute-value\n

If an error occures, the following response can be returned if the attribute is not recognized:

#####400;ATTR;invalid-attribute-name;\n

And the following if the attribute's value is not a valid option:

#####400;OPT;invalid-attribute-name;invalid-attribute-value\n

Finally, for each command, you can get 404 errors:

#####404;NODE;node-id\n #####404;SENSOR;sensor-id\n

---

Creating sensors

You have to create sensors in the embedded arduino code, in the setup function.

public void Arduilink::addSensor(uint id, uint flags, char* description, char* unit);

The following flags are allowed:

Flag	Description	Value
S_INFO	The sensor is able to return the current value (with GET action)	1
S_HIT	The sensor is able to send heartbeats each time a measure is recorded	2
S_ACTION	The sensor is able to receive custom actions like switching on/off	4
S_BATTERY	The sensor is able to gather his own battery level	8

Unit value is an arbitrary string; you must specify a coherent unit according to the measured physical quantity.

Type	Physical quantities	Units
Other	Digital value (State)	boolean, unitless
Other	Analogic value (Dimmer)	numeric value, unitless
Base	Length	meter (m)
Base	Mass	kilogram (kg)
Base	Time	second (s)
Base	Temperature	kelvin (K), degree celcius (C°)
Base	Amount of substance	mole (mol)
Derived	Luminous intensity	candela (cd)
Derived	Angle	radian (rad), degrees (°)
Derived	Frequency	hertz (Hz)
Derived	Force, weight	newton (N)
Derived	Pressure, stress	pascal (Pa)
Derived	Energy, work, heat	joule (J)
Base	Electric current	ampere (A)
Derived	Electric power	watt (W)
Derived	Electric charge	coulomb (C)
Derived	Electric potential difference	volt (V)
Derived	Electric capacitance	farad (F)
Derived	Electric resistance, impedance	ohm
Derived	Electric conductance	siemens (S)
Derived	Magnetic field	weber (Wb)
Derived	Luminous flux	lumen (lm)
Derived	Luminous intensity	lux (lx)
Derived	Area	length * length
Derived	Volume	length * length * length
Derived	Speed	length / time
Derived	Angular moment	mass / time / angle
...	...	...