DMX512 Programmable Theater Lighting Controller

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DMX512 Programmable Theater Lighting Controller
Jeff Sand and Kris Kopel Advisor Dr. Don
Schertz May 8, 2001
2
Outline

• Objectives
• Digital Lighting Control Overview
• System Block Diagram (Hardware)
• Firmware
• Software
• Results

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Objectives

• Generate DMX512 output to control lighting
  devices
• Enable PC control to change dimmer levels
• Develop USB platform for future use
• Write commercial quality firmware, driver, and
  windows software
• In short, Design a complete marketable system
  using a top down approach

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Digital Theatrical Lighting
Console
Lights
Dimmers
Lights
DMX512
Lights
Dimmers
Lights
Intelligent Luminaries
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DMX512 Protocol

• United States Institute for Theatre Technology
  (USITT) standard
• Controls up to 512 dimmers/devices
• Serial and asynchronous bitstream
• 250 kbits/s
• RS-485 physical implementation
• 32 nodes on one chain

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System Block Diagram
Motorola 68376 mController
Input Blocks
Personal Computer
USB Transceiver Philips PDIUSBD12
RS485 Driver MAX483
DMX512 Output
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Microcontroller Interfaces

• Data bus, chip selects, and external IRQ used for
  USB transceiver
• Queued Serial Module (QSM)
• Serial Communication Interface (SCI) for DMX
  output
• Queued Serial Peripheral Interface (QSPI) for
  input blocks
• Internal RAM for data storage
• EPROMs for program code
• Background Debug Mode (BDM) for development
  without a monitor program

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Input Block
QSPI Control Lines
Serial A/D MAX148
Fader Inputs
Out to mController QSM Module
Serial Shift Register 74166
Momentary Push Buttons
Latch 74373
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Firmware

• Written in assembly language
• Interrupt driven
• DMX512 output
• Fader/Button data acquisition
• USB Communication over data bus
• Main program loop for standalone mode only

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DMX Output Stream
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SCI Interrupt Routine
DMX Output Status?
break
data
mark
start
End Break
Output Start Code
Start Break
Last Channel?
no
yes
DMX Output Status lt- Start
DMX Output Status lt- Break
Set Timer
DMX Output Status lt- Mark
DMX Output Status lt- Data
Output Data Byte
Exit ISR
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QSPI Interrupt Routine
Read/Clear Status Register
Read all Buttons
Faders or Buttons?
Buttons
Faders
Read 8 Faders
yes
Last Fader Block?
Reprogram QSPI for Faders
Reprogram QSPI for Buttons
no
Increment Chip Selects
Re-Enable QSPI
Exit ISR
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USB Interrupt Routine
Bus Reset
Handle Reset
Read interrupt register
Suspend Change
Handle Change
no
Data Endpoint In
Data left to send?
Send it
yes
Data Endpoint Out
Read Data into Buffer
no
Control Endpoint In
Data left to send?
yes
Send it
Control Endpoint Out
Exit ISR
Set Address
Device Descriptor
Get Descriptor
Configuration Descriptor
String Descriptor
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Windows Driver

• Windows kernel mode USB driver
• Recognizes and initializes device
• Registers device with Windows to be accessed by
  user applications
• Handles reads from/writes to device
• Plug n Play and Windows power management
  compatible

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Windows Device Detection
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Windows Software

• Three modes of operation
• Direct fader control
• Software dimmer patching
• Programmed lighting queues
• Uses Windows common controls
• Uses Windows timers

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Windows Software
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Results

• Completed DMX512 Output (Hardware and Firmware)
• Adjustable number of channels
• Proper output frequency
• Completed Input Blocks
• (Hardware and Firmware)
• Buttons, Faders, and control circuitry wire
  wrapped onto panel
• One master block and two 8 channel scenes
• Firmware capacity for 128 faders and buttons

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DMX Output Result
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Results

• Wrote a firmware routine for direct external
  fader control with master control, two scenes,
  and crossfade
• Implemented USB firmware (all functions necessary
  for this device)
• Interfaced USB peripheral chip with
  microcontroller on data bus
• Master power switch

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Results

• Wrote functional Windows kernel mode driver
• Wrote windows user application
• Currently does not properly interface with driver
• Tested complete unit with DMX light and it worked
  perfectly
• We plan to test the device in the Bradley theater
  in the near future