Open-Source, Low-Cost, High-Performance Linux Master Controller Plus Ethercat Master Solution Built on the RTOnBoot Framework

With the development of technology, the requirements for real-time synchronization accuracy of buses in modern control systems are becoming increasingly stringent. Therefore, buses such as ModBus and CAN are being used less and less, and the Ethercat bus has become the de facto standard. In fields such as industrial automation, industrial robots, high-precision machining, and humanoid robots, more and more systems are adopting the Ethercat bus with a synchronization cycle of up to 125 microseconds. However, the master station ecosystem in this area is controlled by European and American companies, and these master controller plus master station systems are often quite expensive. Therefore, the market urgently needs a low-cost Linux master controller plus Ethercat master solution with a synchronization cycle of up to 125 microseconds. Chengdu Shian Anxin Technology Co., Ltd. has responded to this demand by launching an open-source, low-cost, high-performance Linux master controller plus Ethercat master solution with a stable synchronization cycle of 125 microseconds and a very low cost.
The software system of the low-cost, high-performance Linux master controller plus Ethercat master solution is built on the multi-core heterogeneous framework RTOnBoot. RTOnBoot is an industry-leading Linux plus RTOS multi-core heterogeneous framework. Its real-time jitter is the lowest among existing Linux or Linux-derived systems, with only 1 microsecond of real-time jitter under idle and only 4 microseconds under heavy load, far superior to Xenomai or Preempt-RT. The software system of the low-cost, high-performance Linux host plus Ethercat master solution is mostly open source. The Ethercat-related parts, including the SOEM protocol stack and real-time network card driver, are open source. Only a small amount of source code related to the RTOnBoot framework is not open source, but it is available.
RTSDK programming interface. The low-cost, high-performance Linux controller plus Ethercat master solution uses the RK3588 processor, which is the preferred choice after comprehensively considering factors such as cost, AI performance, number of cores, processing performance, and ecosystem. The Ethercat synchronization cycle of this low-cost, high-performance Linux controller plus Ethercat master solution can stably reach 125 microseconds. When the motor is rotating, the latency is measured. After one million tests, the maximum sleep latency is 11 microseconds, and the maximum execution latency, including packet sending and receiving, is 20 microseconds. The two maximum latencies combined are only slightly over 30 microseconds, leaving a margin of over 90 microseconds from 125 microseconds. Its real-time performance is undoubtedly excellent among many solutions. The overall cost of the Linux controller plus Ethercat master solution is much lower than other solutions with this performance.
The RTOnBoot framework is easy to program, has RTSDK support, and can be easily integrated into the ROS framework for use in robotic systems.
The Ethercat protocol stack in the low-cost, high-performance Linux host plus Ethercat master solution uses the SOEM protocol stack. We also ported the IGH protocol stack successfully. However, after comparison, we found that the IGH protocol stack's software architecture is more suitable for native Linux. For multi-core heterogeneous architectures, running SOEM on a single RTOS core provides better real-time performance and DC synchronization. Therefore, we no longer maintain the IGH code. However, to enhance the usability of the SOEM protocol stack, we developed ICOS, or IGH Commands over SOEM, which allows IGH commands to be run under Linux.
The RTOnBoot framework boasts optimal performance for large-capacity data exchange between cores, minimizing the number of memcpy calls.
The RTOnBoot framework also features a TRACE mechanism for multi-core collaborative work, facilitating troubleshooting of multi-core issues.