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Software Tools for Interacting with ArtBus, Flash, Processing, Max/MSP and Others

Mon, 03/10/2008 - 15:25 — artbus

Sharing connections and data

  • The ArtBus protocol exists to make highly dissimilar devices able to share physical data connections and a common command and data format. Having a standard method for making connections increases interoperability of componants. 
  • ArtBus messaging tries to work as alike as possible on all platforms. This isomorphism will help hackers orient themselves in going from one programming context to another.
  • The same bug code should run against any bus master language environment, from Pbasic on a Stamp, to Max/MSP.
  • Providing the isomorphism across software environments requires a bridge between the ArtBus and the bus master. This piece of software is called a mediator,  or humorously a transmogrifier.

Mediators (transmogrifiers)

A mediator is a type of bridge, or glue, or interface program that makes programming environments which have quirky (like Max) or hobbled (like Flash) serial I/O capabilities look like normal serial devices to ArtBus.

Mediators have two layers. The lower layer allows application software communication with a port type it cannot access (like RS-232 serial) by emulating a type of port which the software can access (like internet connections). This lower level is sometimes called a com port redirector. The top layer of a mediator modifies the data stream to buffer and reformat the data stream as needed to enable communication.

Mediators for media applications

Some bus masters require a mediator and some do not. There are two types of mediators at present: One impements serial to Open Sound Control (OSC), and the other implements serial to TCP (internet). The OSC transmogrifier works with MAX/MSP™ and PD, and the TCP transmogrifier works with Flash™. Processing doesn't require a transmogrifier but does require a bit of code to be included in the Processing program in order to talk to the ArtBus.

The ArtBus physical connection

The ArtBus physical connection is made over a type of hardware link called RS-485. RS-485 is a type of serial data connection like RS-232 or UART. In desktop computers this connection was supplied by a serial port, also called a com port. Serial ports are no longer included in personal computers, so the function of a serial port is often emulated by a USB-to-serial adapter such as the FTDI.