DMX Implementation
Moog Animatics Class 5 SmartMotor™ DMX Guide, Rev. C
Page 23 of 46
DMX Implementation
The SmartMotor has the ability to accept DMX512 protocol through the RS-485 port. Flexibility
is maintained by allowing the user to assign and accept multiple slots of incoming DMX
protocol — the starting slot and number of slots may be defined by the user.
DMX data packets are unsigned 8-bit integer data. As a result, and to conform to only positive
integer values, incoming slots of 8-bit data are stored into 16-bit signed array variables in
SmartMotor memory.
SmartMotors have predefined 16-bit array data variables consisting of aw[0] through aw
[101]. Therefore, the SmartMotor is limited to 102 DMX channels. The "aw" stands for "array
word" and is an indexed 16-bit signed integer value. If a slot is assigned to an aw[ ] array
variable, the value returned will be between 0 and 255. This assures proper sign convention
for all values. It also allows for easier addition and bit shifting to optimize incoming data.
NOTE:
The SmartMotor is limited to 102 DMX channels.
The user program must read incoming DMX data in the aw[ ] registers and perform all actions
from that data, including motion and/or digital outputs.
For example, if you want to control the position of a theater light, you would:
1. Select an unused DMX controller channel,
2. Program the base address in the SmartMotor aligned with that particular channel,
3. Write a program that reads the corresponding array variable in the SmartMotor,
4. Assign corresponding parameters in the motor, including position, velocity, acceleration
and torque, call out a specific subroutine, and more.
By using the SmartMotor, the entire motion control system requires less cabling and becomes
more compact because no control cabinet is needed. Further, additional axes can be added as
needed.
Data Storage and Usage
Address information for the DMX protocol can be stored in one of the following ways:
l
It can be "hard coded" into the program, or
l
The VST/VLD commands can be used to store/retrieve this information
to/from the desired SmartMotor memory location.
It is up to the system programmer to select the method that works best for the application.
NOTE:
Technically, there is no "address" for a DMX slave device. The slave device
sees all (possibly 512 bytes) of the data and decides which part it wants to use.
