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AN1076 Using a PIC® Microcontroller for DMX512 Communication Author: Parthiv Pandya Microchip Technology Inc. place of auto-transformers, becoming quite popular, particularly the 0-10V analog consoles. Still, this system had three major drawbacks: 1. 2. 3. It was prone to noise. Dimming could be nonlinear depending on different kinds of lamps. A separate control wire was required for each lamp. INTRODUCTION DMX512 is a communication protocol used in most professional theater lighting components such as dimmers, scanners, moving lights, strobes, etc. This application note presents a solution to transmit and receive the DMX512 communication protocol that can be implemented using any PIC® microcontroller offering a Universal Asynchronous Receiver Transmitter (UART) module. In particular, the PIC18F24J10, a general purpose device, was used in the code examples provided with this application note. It provides 1024 bytes of data memory, which allows the demonstration code to store the data for the entire 512 channel buffer (although this is not required for the typical application). Only an external RS-485 compatible transceiver is required to complete the application schematic. The DMX solution is provided in two parts: 1. DMX512 Transmitter: This part will explain how to generate and transmit the DMX512 packets. This is divided into two subsections: (a) how to generate and transmit the DMX512 packets and (b) a demo program that shows how to send commands to a DMX512 light dimming receiver. 2. DMX512 Receiver: This part will explain how to receive the DMX512 packets. Once more, it is divided into two subsections: (a) how to receive the data and (b) a demo program that sends the received data to the PWM module to control the brightness of a LED. As computer technology became more cost effective, new digital consoles came to the market and with them the need for a new standard that would allow equipment from different manufacturers to interoperate. The United States Institute of Theatre Technology, USITT, first developed the DMX512 protocol in 1986 as a standard digital interface between dimmers and consoles, later expanded and improved in 1990. The current version, known as DMX512-A, has also been adopted as an American National Standards Institute (ANSI) standard (E1.11). The development of DMX512-A is currently managed by the Entertainment Services & Technology Association (ESTA). You can obtain (purchase) a copy of the protocol specifications from the www.esta.org web site or the www.ansi.org web site. ANATOMY OF THE DMX512 PROTOCOL DMX512 (an acronym for Digital MultipleX), is extremely simple, low cost and relatively robust. Due to these advantages DMX512 has gained a great popularity. As the name suggests, it can support up to 512 separate control channels/devices. It is a unidirectional asynchronous serial transmission protocol which does not provide for any form of handshake between receiver and transmitter, nor does it offer any form of err