Firmata - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 264

process that data. Data is received directly on the serial port. To see if data is
waiting, use available() :

result = Firmata.available();

This function does not take any parameters and returns true if one or more
bytes are waiting to be processed. To process data, use processInput():

Firmata.processInput();

Typically, you would use both functions together:

while(Firmata.available())
{
Firmata.processInput();
}

The Firmata library hides all the complicated parts of receiving data, including
the data storage and processing. The library automatically decodes messages and
enables you to perform actions on the data received using a system of callbacks.

Callbacks

Firmata works by using a system of callbacks , routines that are called when a
specii c action is performed, or in this case, when a specii c message is received.
Callbacks are highly customizable, and you can write a callback to perform almost
any action you want simply by creating a function. Callbacks are put in place
using an attach function; in the case of the Firmata library, it is called attach() :

Firmata.attach(messagetype, function);

Table 16-1 lists the messagetype parameter, which is one of the constants. The
function parameter is the callback function that you have written.

Table 16-1: Callback Constants

CONSTANT USE

ANALOG_MESSAGE Analog value of a single pin

DIGITAL_MESSAGE Digital value of a digital port

REPORT_ANALOG Enables or disables the reporting of an analog pin

REPORT_DIGITAL

Enables or disables the reporting of a digital port

SET_PIN_MODE Change the mode of the selected pin (input, output, and so on)

FIRMATA_STRING Used for receiving text messages

SYSEX_START Used for sending generic messages

SYSTEM_RESET

Used to reset fi rmware to default state