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Cyber-physical systems (CPS) increasingly require real-time, high bandwidth data communication and processing. To address this, Time Sensitive Networking (TSN) provides latency-bounded data transmission at one or more gigabits-per-second throughput. However, it does not commonly connect directly to I/O devices, such as sensors and actuators. In contrast, Universal Serial Bus (USB) is ubiquitous for device I/O, but has yet to be widely adopted for host-to-host networking. This paper considers the use of a common USB software stack for both device I/O and host-to-host communication. We compare against a system using USB for device I/O and TSN for host-level networking. Our findings show that a unified approach using USB results in reduced software complexity, simplified bus coordination, and more effective mitigation of priority inversion when transferring data across multiple bus segments. Experiments show that end-to-end latency is within expected delay bounds, and is reduced if the same USB software stack is used for all communication with a given host. This suggests that bridging challenges exist in current systems, which are solved by either extending a high-bandwidth bus such as TSN to support device I/O, or enhancing USB with improved networking capabilities.
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Real-Time USB Networking and Device I/O
Multicore PC-class embedded systems present an opportunity to consolidate separate microcontrollers as software-defined functions. For instance, an automotive system with more than 100 electronic control units (ECUs) could be replaced with one or, at most, several multicore PCs running software tasks for chassis, body, powertrain, infotainment, and advanced driver assistance system (ADAS) services. However, a key challenge is how to handle real-time device input and output (I/O) and host-level networking as part of sensor data processing and control. A traditional microcontroller would commonly feature one or more Controller Area Network (CAN) buses for real-time I/O. CAN buses are usually absent in PCs, which instead feature higher bandwidth Universal Serial Bus (USB) interfaces. This article shows how to achieve real-time device I/O and host-to-host communication over USB, using suitably written device drivers and a time-aware POSIX-like “tuned pipe” abstraction. This allows developers to establish task pipelines spanning one or more hosts, with end-to-end latency and throughput guarantees for sensor data processing, control, and actuation.
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- PAR ID:
- 10451250
- Date Published:
- Journal Name:
- ACM Transactions on Embedded Computing Systems
- Volume:
- 22
- Issue:
- 4
- ISSN:
- 1539-9087
- Page Range / eLocation ID:
- 1 to 38
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1145/3604429
