DALI Controller Settling Time for Collision Avoidance
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Solution Overview
Problem
In digital lighting control systems using the DALI bus, the coexistence of master devices with different capabilities leads to collisions and unreliable operations when a Single Central Master is connected to Multi Masters, due to the inability of the Single Central Master to detect collisions, resulting in delayed sensor responses and message corruption.
Innovation Solution
A method and device arrangement that allows master devices with different capabilities to communicate on the same DALI bus by implementing a controller device that operates as a Single Central Master, which waits for a predefined settling time after observing a preceding forward frame before transmitting, and Multi Masters that test for bus availability before transmitting, ensuring collision avoidance without requiring extensive real-time capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a Single Central Master operates with simple timer-based transmission without collision detection, then device complexity is reduced and ease of operation is improved, but reliability deteriorates due to inability to detect collisions with Multi Masters
Solution Approach 1:
The patent introduces a mediator mechanism where the Single Central Master waits for a predefined settling time after observing a preceding forward frame before transmitting. This settling time acts as an intermediary period that allows Multi Masters to detect the frame and initiate their own transmissions if needed, preventing collisions while maintaining simple timer-based operation without complex real-time collision detection capabilities
Solution Approach 2:
The Single Central Master performs a preliminary action by waiting for the settling time before transmitting its own forward frame. This preliminary waiting period enables Multi Masters to observe the bus state and prepare their transmissions accordingly, avoiding collisions before they occur rather than detecting them during transmission
2Productivity
If a Single Central Master transmits very frequently to monitor the system and resend information, then productivity is improved through frequent updates, but reliability worsens due to increased collision risk with Multi Masters
Solution Approach 1:
The settling time wait acts as an intermediary mechanism that reconciles the need for frequent transmissions with collision avoidance. The Single Central Master can maintain high productivity by quickly transmitting when the bus is clear, while the settling time ensures that frequent transmissions do not collide with Multi Master transmissions that may be initiated during the monitoring period
3Reliability
If Multi Masters operate with collision detection capability, then reliability is improved through collision avoidance, but device complexity increases due to required real-time capabilities
Solution Approach 1:
The patent applies preliminary action by having Multi Masters observe the bus for the settling time period before initiating transmission. This allows them to detect the presence of a Single Central Master frame in advance and defer their transmission, achieving collision avoidance without requiring complex real-time interruption handling during the critical transmission window
Data Source
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AI summary
A method, a controller device and a computer program are provided for transmitting forward frames (601, 602, 701, 704, 709, 801, 805, 1201, 1205) from a controller of a first kind (400) on a lighting control bus (402) to which also controllers of a second kind (404) are allowed to be coupled. After transmitting a first forward frame (701, 801, 1201) on the lighting control bus (402) the controller of first kind (400) waits for a delay (703, 708, 804) that is longer than a predefined longest settling time between frames applied by said controllers of second kind (404), before transmitting a second forward frame (704, 709, 805).