MISC-TN-022: Advanced controller for DMX / RDM lighting applications
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Contents
History[edit | edit source]
| Version | Date | Notes |
|---|---|---|
| 1.0.0 | May 2022 | First public release |
Introduction[edit | edit source]
This Technical Note (TN for short) illustrates the concept behind a custom product developed by DAVE Embedded Systems for a customer operating in the professional lighting market. This project is a useful use case for showing some interesting technologies that can address effectively common requirements in the world of embedded systems for industrial applications.
Overview[edit | edit source]
The following image depicts the product's block diagram.
TBD
Basically, the product is a dual-role device: it can operate either as controller or as recorder.
When working as controller, it feeds slave devices (stage lighting dimmers, special effects machines, etc.) with DMX streams. DMX data can be generated programmatically on the fly or can be retrieved from previously recorded streams.
When working as recorder, the product "sniffs" and stores DMX data traffic traveling on the connected buses. Each DMX frame is stored with an associated timestamp. Thus, the data stream can be played at a later time with the same timings of the original one.
As shown in the block diagram, the product features a rich set of I/O's ranging from the DMX/RDM channels to network interfaces.
The core of the system is the Orca SoM, which in turn is built around the i.MX8M Plus system-on-chip by NXP.
Heterogeneous asymmetric multiprocessing[edit | edit source]
From the computational standpoint, there are two domains running two different operating systems. In this regard, the resulting architecture is an example of heterogeneous asymmetric multiprocessing as it is based on different types of cores, namely the ARM Cortex-A53 and the ARM Cortex-M7.
The system architect chose this implementation because it is convenient to satisfy the diversified product's requirements. In particular, the DMX/RDM subsystem must meet real-time requirements in order to be compliant with the DMX/RDM standards. The DMX/RDM subsystem consists of an ARM Cortex-M7 core working in tandem with an FPGA.
On the other side, the M7 core is connected to an FPGA through an I2S bus. Even though this bus is conceived for digital audio streams, it fits very well for conveying the data to/from the DMX/RDM channels.
The A53-centred domain runs a Yocto Linux distribution. The product's main application is executed in this domain. In particular, this application integrates the business logic and implements the GUI. Also, it deals with all the peripherals and interfaces not having real-time constraints such as the temperature sensor, the gyroscope, the Ethernet ports, etc.
The Linux domain is widely scalable in terms of computational power as multiple versions of the SoC are available featuring a different number of A53 cores (1, 2, or 4). These versions are ballout compatible, thus one hardware board fits them all.
Real-timeness[edit | edit source]
As stated previously, the ARM Cortex-M7 core and the FPGA are the building blocks of the DMX/RDM domain.
A real-time operating system (FreeRTOS) runs on the M7 core. The application executed on top of the RTOS communicates with the Linux domain through RPMsg-Lite, a lightweight implementation of the Remote Processor Messaging (RPMsg) protocol according to NXP documentation.
Security[edit | edit source]
crypto chip
2 devices
TBD attendere call con Microchip
