Using XC836 EZ-Kit for DMX512 Transmitting Device - description

XC82x/XC83x
DMX512 Transmitting Device with
XC836
AP08132
Application Note
V1.0, 2012-10
Microcontrollers
Edition 2012-10
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2012 Infineon Technologies AG
All Rights Reserved.
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DMX512 Transmitting Device with XC836
AP08132
XC82x/XC83x
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Application Note
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DMX512 Transmitting Device with XC836
AP08132
Table of Contents
1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
2.1
2.2
2.2.1
2.2.2
2.3
Overview of DMX512 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Physical Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
XLR-5 Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ground Referenced Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DMX512 Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
3.1
3.2
3.2.1
3.2.2
3.2.3
3.2.4
Implementing A Simple DMX512 Transmitting Device with XC836 Easy Kit . . . . . . . . . . . . . . . . 9
Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Software Abstraction Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Interrupt Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Source Code Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Transmitted DMX512 Signal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4
4.1
4.2
4.3
DMX512 Transmitting Device Code Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuring DMX512 Slots to be Transmitted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Configuring XC836 pins for RS-485 Interface Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Setting Scenes for Demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
13
13
14
5
5.1
5.2
5.3
5.4
5.5
5.6
Evaluating DALI - DMX512 Board for LED Color Control Application . . . . . . . . . . . . . . . . . . . . .
Connecting the Boards in a Daisy-Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Setting the DMX512 Address with DIP switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connecting the Transmitting Device to the Daisy Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Powering Up the Receiving Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Powering Up the Transmitting Device from USB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Controlling LED Color with the Transmitting Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
15
15
16
16
17
17
6
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5
5
6
6
7
7
Appendix - RS485 Interface Board Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Appendix - DMX512 Software Stack Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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Introduction
1
Introduction
DMX512 is a communication protocol commonly used in stage lighting applications. It describes the digital data
transmission between the controller and the stage equipment, such as a washlight, moving head, or fog machine
for example. The E1.11-2008 USITT DMX512-A protocol is maintained by ESTA (Entertainment Service and
Technology Association).
This application note describes the implementation of a DMX512 transmitting device using the XC836 Easy Kit
from Infineon. We start with an overview of the DMX512 communication protocol, where the system architecture
and protocol structure for transmitting device are explained, then discuss the implementation using the XC836
Easy Kit, and finally describe a use-case demonstration with the integrated DALI-DMX512 board to control the onboard RGB LED via the DMX512 protocol.
2
Overview of DMX512
DMX512 is a packet-based, asynchronous, serial and unidirectional communication protocol. Because there is no
error checking or correction mechanism specified in the standard, this makes it relatively simple, but also means
that it is unsuitable for safety-critical applications.
DMX512 uses differential signals for communication specified by the RS-485 standard. Therefore, it has good
immunity against noise and is able to communicate at relatively long distance (up to 1200 meters). However, it
also inherits the limitation of RS-485 which allows only up to 32 devices to be connected to the same
communication line.
2.1
System Overview
A DMX512 system consists of one master device (transmitting device) connected to multiple slave devices
(receiving devices) in "daisy chain" manner as illustrated in Figure 1 below.
Figure 1
DMX512 System connected in Daisy Chain
A unique address must be assigned to each slave device by configuring the DIP switch embedded on each device.
The address may range from 1 to 512, depending on how many devices are connected and how many DMX512
slots/channels are consumed by each device. For example, an RGB-LED wallwasher may consume one DMX512
slot for each color. If its address is set at 10, it will consume slot 10, 11 and 12. The address for the next device
must be set to 13.
A termination resistance typically of 120Ω is connected at the furthest slave device to prevent signal reflection.
In the case where more than 32 devices are required in a system, an in-line device, such as optosplitter, can be
used.
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Overview of DMX512
2.2
Physical Layer
The standard specifies the physical layer of DMX512 to consist of the connector configuration and the circuit
topology. DMX512 system uses XLR-5 connectors, as shown in Figure 2. Transmitting device uses Ground
Referenced Topology while receving device uses Isolated Topology. In this Application Note, only the physical
layer of the master device/transmitting device is discussed.
2.2.1
XLR-5 Connector
The standard specifies a female XLR-5 connector shall be used in transmitting device. This is to create the daisychain topology that ensures the continuity of communication from the transmitting device to the last receiving
device.
Figure 2
XLR-5 Connector Pinouts. Male-type is on the left and Female-type is on the right.
The following Table 1 specifies the connection for the transmitting device:
Table 1
DMX512 Pinout on XLR-5 Connector
Pin Number
Signal Name
Description
1
Common Reference
Data Link Common
2
Data 1+
Primary Data Link
3
Data 1-
4
Data 2+
5
Data 2-
Secondary Data Link (Optional)
In a typical DMX512 application, only Primary Data Link (DATA1+ and DATA1-) and Common Reference are
used.
The Secondary Data Link is not used and reserved for future use. Therefore, it is common to find some lighting
fixtures that use XLR-3 connectors.
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Overview of DMX512
2.2.2
Ground Referenced Topology
The standard specifies the use of ground referenced topology in the transmitting device circuit, as illustrated in the
Figure 3 below.
Figure 3
Ground Referenced Topology as specified in the standard
2.3
DMX512 Protocol
As the name suggests, there are 512 "pieces of information" carried in a DMX512 packet. Each "piece of
information" is also known as a slot or channel, which consists of 1 start bit, 8 data bits and 2 stop bits. A Reset
Sequence consisting BREAK, MAB and NULL Start Code must be transmitted before the slots.
Figure 4 illustrates a DMX512 packet.
Figure 4
DMX512 Packet
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Overview of DMX512
The timing requirements for transmitting device are shown in Table 2.
Table 2
Timing Requirements for Transmitting Device
Signal
Min. Value
Typ. Value Max. Value Description
Bit Rate
245 kbps
250 kbps
255 kbps
Bit Time
3.92 μs
4 μs
4.08 μs
BREAK
92 μs
176 μs
-
A falling edge transition followed by a low of at least 88 μs
followed by a rising edge.
MAB
12 μs
-
<1s
Mark After Break - The period of time measured from the
rising edge at the end of BREAK to the falling edge of the
start bit of the START Code.
MTBS
0
-
<1s
Mark Time Between Slot - The period measured from the
end of the second stop bit (bit 9) of the previous slot to the
falling edge of the start bit of the current slot.
MBB
0
-
<1s
Mark Before Break - The period measured from the end of
the second stop-bit of the last slot to the falling edge of the
next BREAK.
-
1.00 s
The period between two BREAKs
BREAK-TO- 1204 μs
BREAK
Application Note
Transmission rate for DMX512 protocol.
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Implementing A Simple DMX512 Transmitting Device with XC836 Easy Kit
3
Implementing A Simple DMX512 Transmitting Device with XC836
Easy Kit
A simple DMX512 transmitting device can be implemented using XC836 Easy Kit because it has on-board
capacitive-touch pads and four 7-segment LEDs. This can be used as a simple user interface, where the user can
input command and know the value of slots being transmitted. Both are controlled using LEDTS, an integrated
peripheral specifically designed for capacitive-touch and LED control application.
The code for transmitting DMX512 signal is implemented using Timer 2 and UART. Timer 2 generates the BREAK,
MAB, MBB and MTBS signals, while UART transmits the DMX512 slots.
3.1
Hardware
DMX512 uses differential signals for communication. Therefore, an RS-485 interface board is built to convert MCU
signals into differential signals. The board is designed with the same form factor to the Easy Kit connector so that
it can fit nicely on it.
Figure 5 shows the XC836 Easy Kit with RS-485 interface board. The schematic can be found in Figure 19.
Figure 5
XC836 Easy Kit with RS-485 Interface Board as DMX512 Transmitting Device
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Implementing A Simple DMX512 Transmitting Device with XC836 Easy Kit
3.2
Software
The code uses the following XC836 peripherals:
•
•
Timer 2 and UART are used to transmit the DMX512 signal
LEDTS is used to take in and display user input in a form of addresses and slot values.
3.2.1
Software Abstraction Layers
Figure 6 shows the software abstraction layers which illustrates the processing of DMX512 signal.
Figure 6
Software Abstraction Layer
DMX512 transmission is controlled by the user via the touch pads. It runs continuously until the user disables it. It
is posible to change the slot values and slot address ‘on-the-fly’. Timer 2 provides BREAK, MAB and “window time”
for slot transmission. This window time is always greater thanthe slot time (44μs). The difference between these
two timings is the MTBS (Mean Time Between Slots).
UART is enabled during MAB transmission to prepare for slot transmission. At every UART Transmit Interrupt, the
slot index is increased. When it reaches the specified packet length, UART is disabled and the DMX512 pin is
reinitialized back to transmit the next DMX512 packet.
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Implementing A Simple DMX512 Transmitting Device with XC836 Easy Kit
3.2.2
Interrupt Timing Diagram
This process is summarized in Figure 7, the interrupt timing diagram.
Figure 7
Interrupt Timing Diagram
3.2.3
Source Code Files
The source code files used in the transmitting device are summarized in the following Table 3.
Table 3
List of Source Code Files for DMX512 Transmitting Device Code
Code Name
Description
DMX512_MASTER_C
ONFIG.H
Contains Defines, subroutine declarations and configuration; e.g. DMX512 transmit pin,
RS-485 Data Enable pin, number of transmitted slots, scene demo setting, etc.
MAIN.C
Contains pin initializations and slot values initialization.
T2.C
Timer 2 initialization and Timer 2 Interrupt subroutine (TF2 flag) to transmit DMX512
packet (BREAK, MAB and slots).
UART.C
UART Initialization, the interrupt subroutine (TI flag) containing reset sequences for retransmitting DMX512 packet.
SHARED_INT.C
Contains GUI processing routines to decode user input from touch pads and display to
7-segment LEDs
IO.C
GPIO initialization subroutines. It follows the assigned DMX512 pin in the
DMX512_CONFIG.H
LTS.C
LEDTS peripheral initialization.
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3.2.4
Transmitted DMX512 Signal Characteristics
The following Table 4 shows the characteristics of the transmitted DMX512 signal. Note that the measurement
values presented are the average values.
Table 4
Transmitted DMX512 Signal Characteristics
Signal
Recommended Value
Bit Rate
250 kbps
Bit Time
4 μs
Number of slots
24
BREAK
184 μs
MAB
44 μs
MTBS
77 μs
MBB
80 μs
BREAK-to-BREAK
3132 μs
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DMX512 Transmitting Device Code Configuration
4
DMX512 Transmitting Device Code Configuration
This chapter describes the configuration of the implemented software stack. All the settings can be found in
DMX512_Master_Config.h
4.1
Configuring DMX512 Slots to be Transmitted
The user can configure the number of DMX512 slots to be transmitted by changing the #define
DMX_PACKET_LENGTH to the desired number, as shown in Figure 8. The defined packet length includes
START code (slot 0). In this example 24 slots are available for operation, although the packet length is set to 25.
Figure 8
Configuring DMX512 Slots to be Transmitted
4.2
Configuring XC836 pins for RS-485 Interface Board
There are two pins required to control RS-485 communication, namely DATA_ENABLE (DE) and DATA_INPUT
(DI), as shown in Figure 9. This implementation uses P3_0 and P0_7 for DE pin and DI pin, respectively.
Figure 9
Configuring XC836 pins for Controlling RS485 Interface Board
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DMX512 Transmitting Device Code Configuration
4.3
Setting Scenes for Demonstration
It is common in stage lighting applications to find the lighting fixtures set and frozen to specific values in a set
period of time. This process is known as creating Scenes. Our implementation is equipped with some simple
demonstration scenes that work with the DALI-DMX512 boards from Infineon. Please refer to the document ref.
AP08131 for more details on these boards.
The demonstration scenes are summarized in the following Table 5 below. Further explanation on how to evaluate
the scenes can be found in Section 5.
Table 5
Demo Scenes
Scene #
Description
1
Set slave devices LED to all red
2
Set slave devices LED to all green
3
Set slave devices LED to all blue
4
Set slave devices LED to display red, yellow, green
The demo scenes can be disabled by commenting out the #define ENABLE_SCENE, as shown in Figure 10
below.
Figure 10
Enable/Disable Scene
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Evaluating DALI - DMX512 Board for LED Color Control Application
5
Evaluating DALI - DMX512 Board for LED Color Control Application
The DALI-DMX512 Board from Infineon is a receiving or slave device that contains the two common lighting
protocols, DALI and DMX512. The board is designed to demonstrate an LED Color Control application on both
protocols. This chapter is intended as a step-by-step guide for users to evaluate this board.
5.1
Connecting the Boards in a Daisy-Chain
A simple twisted pair of shielded wires can be used to connect the boards. The diagram inserted in the top-left of
the following Figure 11 shows the wiring connection.
Figure 11
Two Boards connected in Daisy Chain
5.2
Setting the DMX512 Address with DIP switches
In a typical DMX512 device, the user can set the DMX512 address using DIP switch, where DIP switch #4 refers
to the Least Significant Bit (LSB) of the address. The following Figure 12 shows an example where the board is
set to Address 11.
Figure 12
Setting DMX512 Address to 4
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Evaluating DALI - DMX512 Board for LED Color Control Application
5.3
Connecting the Transmitting Device to the Daisy Chain
Once the address of each board is set, the transmitting device can be connected as shown in Figure 13.
Figure 13
Connecting Transmitting Device with Receiving Devices
5.4
Powering Up the Receiving Devices
Figure 14 shows the receiving devices being powered up from 5V power supply with on-board LED turned on.
Figure 14
Powering the Receiving Devices
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Evaluating DALI - DMX512 Board for LED Color Control Application
5.5
Powering Up the Transmitting Device from USB
The transmitting device requires 5V DC and is powered from USB, as shown in Figure 15.
Figure 15
Powering the Transmitting Device via USB
5.6
Controlling LED Color with the Transmitting Device
Figure 16 and Figure 17 show the touch pads and the 7-segment LED display functions on the transmitting
device.
Figure 16
XC836 Easy Kit Touch Pads
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Evaluating DALI - DMX512 Board for LED Color Control Application
Figure 17
7-Segment LED display functions
The LED to indicate transmission will only light up when there is a DMX512 signal transmission.
The following Table 6 describes the functionality of each touch pad.
Table 6
Touchpad Descriptions
Touchpad Name
Value Range Description
Next Address
0 - 24[DEC]
Go to next/previous slot address. For demonstration purposes, only
24 slots are supported by the transmitting device.
0 - FF [HEX]
Increase/Decrease current slot values. The value is represented as
hexadecimal.
Fine/Coarse
-
Adjust the resolution of Incr/Decr Slot Value. Selecting Coarse Mode
will modify the 2nd digit of Slot Value while Fine Mode will modify the
1st digit of the Slot Value. Default mode is Coarse Mode.
START/STOP DMX512
-
Start/Stop DMX512 Transmission
Next Scene
0 - 99 [DEC]
Go to the next/previous predefined scene.
-
Set the selected scene to the receiving devices. Pressing this button
will automatically enable the DMX512 transmission.
Prev Address
Incr Slot Value
Decr Slot Value
Prev Scene
Set Scene
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Summary
The following Figure 18 shows the complete setup of DMX512 system for RGB-LED color control application.
Figure 18
Complete Setup of DMX512 System
The user can now control the LED color on each board from the transmitting device. For example, when the slot
value of address 04 is increased, the second board will display brighter red, while increasing the slot value of
address 08 will make the third board display brighter green.
6
Summary
This application note has described the implementation of a simple DMX512 transmitting device using the XC836
Easy Kit. For a complete DMX512 solution, please also refer to the AP08131 detailing the receiving device.
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References
7
References
[1]
ANSI ESTA E1.11 - 2008 “Asynchronous Serial Digital Data Transmission Standard for Controlling Lighting
Equipment and Accessories”
[2]
XC82x User Manual version 1.2
[3]
XC83x User Manual version 1.1
[4]
AP08108 “Programming the BMI Value in the XC82x and XC83x Products”
[5]
AP08131 “DMX512 Receving Device using XC836”
[6]
AP08102 “DALI Control Gear Software Stack”
[7]
AP08114 “DALI Control Device using XC836”
[8]
AP08104 “Guide to using the DALI LightNet Tool”
[9]
AP08105 “DALI Demo using Touch Sense Control”
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References
Appendix - RS485 Interface Board Schematic
Figure 19 and Figure 20 show the schematic and Layout of of RS485 Interface board.
Figure 19
RS485 Interface Board Schematic
Figure 20
RS485 Interface Board Layout
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References
Appendix - DMX512 Software Stack Flowchart
The following Figure 21, Figure 22 and Figure 23 shows the flowchart from each peripheral that is used to create
DMX512 Master Code.
Timer 2 Overflow Interrupt
Timer 2 Overflow Interrupt
Clear Interrupt Flag
Set T2 period for MAB transmission
State = TRANSMIT_MAB
Y
(BREAK transmitted)
Set DMX512 pin to High for MAB
N
Y
Set T2 period for slot transmission window
Y
Y
Set DMX512 pin to Low to transmit Break
(Reinitialization is set at UART Interrupt)
Set T2 period for BREAK transmission
(MAB transmitted)
Proceed to next state (TRANSMIT_SLOTS)
Executed only if Demo Scene is enabled
EnableScene bit
N
State = TRANSMIT_SLOTS
Initialize UART peripheral
Transmit Slots
Demo Scene
N
State = BREAK
(all slots transmitted or transmission enabled)
Proceed to next state
(TRANSMIT_MAB)
N
RETURN
Figure 21
Timer 2 Flowchart
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References
UART Transmit Interrupt
UART Interrupt
Clear TI flag
Increase slot index
Slot index > Packet Length
Y
Reinitialize DMX512 pin as GPIO
Reset Slot Index
Transmit enabled
N
Initialize Timer 2 period
Stop Timer 2
Set DMX512 pin to High
N
Set State = TRANSMIT_BREAK
Y
RETURN
Figure 22
UART Flowchart
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References
Touch Pad pressed
LEDTS Interrupt
Clear Interrupt Flag
Switch (Pad)
Previous
Address
Decrease
Address index
Update Display
Next
Address
Increase
Address Index
Update Display
Increase
Slot Value
Fine Resolution
Increase Slot Value by 0x01
Y
Increase Slot Value by 0x10
N
Decrease
Slot Value
Fine Resolution
Decrease Slot Value by 0x01
Y
Toggle Transmit DMX512 bit
Update Display
Display DMX512 address lower digit at LED 2
Transmit bit
is set
Y
Set DMX512 pin to Low
to transmit BREAK
Resolution
Transmit DMX512
Turn on LED indicator
Display DMX512 higher nibble at LED 3
Turn off LED indicator
N
Toggle Resolution bit
Update Display
Display DMX512 address higher digit at LED 1
Decrease Slot Value by 0x10
N
Start/Stop
DMX512
Update Display
Resolution bit
is set
Y
Display DMX512 lower nibble at LED 4
Lower digit is brighter
RETURN
Higher digit is brighter
N
Executed only if Demo Scene is enabled
Previous
Scene
Stop DMX512 transmission
Decrease Scene Index
Update Scene
Next
Scene
Stop DMX512 transmission
Increase Scene Index
Update Scene
Set
Scene
Enable Scene bit
Turn on DMX512 transmission
Update Scene
RETURN
Figure 23
LEDTS Flowchart
Application Note
24
V1.0, 2012-10
w w w . i n f i n e o n . c o m
Published by Infineon Technologies AG