Modbus TCP/DMX 2 channel converter - MIDAM CDMX01
Converter that translates Ethernet protocols into Digital Multiplex (DMX) signals to control lighting fixtures. This serial converter acts as a Modbus TCP server, controlling up to 1024 lights or other DMX compatible devices simultaneously. It also acts as a DMX sniffer, reading packets sent by a DMX controller on a DMX bus and returning the data as Modbus TCP server registers.
- Control of lighting fixtures
- Operates as a Modbus TCP server
- Control of up to 1024 lights or other DMX-compatible devices
- DMX sniffer functionality
- Data conversion into Modbus TCP server registers
Function
CDMX01converter generate serial signals in a format called DMX512, the lighting controller output is connected to a light fixture. Each DMX capable light fixture has a DMX input/ output. It is a master-slave system where the lighting controller acts as the master, and the light fixture acts as a slave to the controller, but as a master to the next light fixture that is attached in a row. The device acts as a DMX master and can control up to 2x 512 DMX slaves. In Modbus communication topology the device acts as a slave (server) device. It receives commands from a Modbus TCP master (client). the typical client is a PLC. The Modbus data are translated to DMX commands for 2 independent DMX channels and sent to the RS485 buses with DMX512-A protocol. The DMX telegram is sent immediately after writing into the Modbus registers, and optionally on a periodical basis according to the Period Modbus register setting. The period time is configurable in the range of 0.1 to 65.5 s. All parameters and functions of the converter are set over its web interface (http protocol) at TCP port 80. The devices web pages are used for configuration, setup of current and default values of the DMX channels, and for device diagnostics. The web interface and FTP server can be switched off on a HW basis (via USR switch) to ensure extra security of the device. The Ethernet interface switches automatically between 10 and 100 Mbps.
Application
- Direct DMX bus control
- DMX bus maintenance and configuration
- Web-based remote control of the DMX bus
- Wired integration into SCADA systems
Design notes
The PLC controls the DMX lights according to data written into the CDMX01 Modbus registers. In a Sniffer mode the device does not send any data to DMX, and only reads telegrams from the DMX controller (master device). The data are written into the Modbus table. A Modbus TCP client (master), can read these data from the converter’s Modbus table and process them accordingly. The Sniffer mode makes possible to control 3rd party devices, connected to the PLC, over a DMX controller then. In this mode, the expected DMX telegram length should be set in the Modbus register (Size). If the packets are shorter than specified in the Size register, the converter learns the end of the telegram according to the start byte of the next telegram, or space between telegrams longer than 1 s. A DMX channel always works in the specified mode only. There must be only one Master device on a DMX bus. The Master and Sniffer modes can be combined intentionally at both channels (Master – Master, Sniffer – Sniffer, Master – Sniffer, Sniffer - Master).