Dilin Anand from EFY in talk with Rick Wietfeldt, MIPI Alliance Technical Steering Group Chair and Ken Foust, MIPI Alliance Sensor Working Group Chair over MIPI I3C sensor interface for mobile, IoT and automotive system designs, its uses and applications.
Q. Considering MIPI Alliance’s goal is to speed up the evolution of mobile and mobile-influenced products, what do you expect to be the state of these devices in 2023 (after leveraging enhancements that MIPI specifications are providing)?
A. Mobile augmented and virtual reality (AR/VR) is only in its infancy today, and by 2023 we expect it to be mainstream in mobile and other ecosystems such as automotive. It uses a combination of display, camera, sensors and touch peripherals, many of whose interfaces were pioneered by MIPI Alliance (e.g. high-speed display and camera) and most recently the MIPI I3C interface for broad use in sensors, including touch sensors.
Another example, a car doesn’t seem like a space-constrained device, but it actually is. Automakers scrutinize every rupee, dollar, yen and euro because cost is a huge factor in a vehicle’s addressable market. MIPI Alliance’s specifications are not only addressing challenges in the mobile world, but are also being widely used by automakers and their suppliers in their designs too.
Q. What are the top 5 things that those transitioning from I2C or SPI to MIPI I3C should keep in mind?
A. MIPI I3C unifies many key attributes of I2C and SPI while providing a new, high-performing, very low power solution.
1. MIPI I3C uses a base two-wire I2C-compatible interface, which reduces pin count and signal paths to offer system designers less complexity and more flexibility.
2. MIPI I3C supports an effective data rate up to 33.3 Mbps leveraging higher performance high data rate modes on a base 12.5 MHz clock, offering a substantial leap in performance and power efficiency compared with previous options.
3. Devices can interrupt the host over the two I3C wires via an in-band interrupt mechanism, reducing the need for dedicated additional interrupt wires.
4. It provides synchronous and asynchronous time stamping to improve the accuracy of time-sensitive applications that use signals from various sensors.
5. Additional technical highlights of MIPI I3C include multi-master support, dynamic addressing, common command-code compatibility and a uniform approach for advanced power management.
Q. In which use cases/applications would you say that MIPI I3C is a no-brainer?
A.Smartphones – The many sensors packed into modern smartphones are enabling advanced features like activity recognition, pedestrian navigation, health and fitness tracking capabilities and others. As the trend for adding more sensors continues, the implementation is quickly becoming unmanageable. High-end smartphones already have 10 sensors or more, and can require up to 20 signal lines.
The fact that some sensors are always active and that sensor data is always being transferred between devices, requires a very low power communication interface like MIPI I3C.
Internet of Things (IoT) devices are making everyday items like homes and cars smarter to improve our daily lives. This would not be possible without the use of sensors to gather and analyze data from the world around us. In typical IoT systems, the sensor hubs act as the master and control the communication at all times, for both I2C and SPI. For these systems, MIPI I3C can replace all other communication interfaces with two wires. It will allow slave devices to initiate communication with simple in-band interrupt requests and enable peer-to-peer communication for smart sensors that want to read from or write to each other. This peer- to-peer communication does not require any interaction from the master, except providing the bus clock.
Wearables are characteristically small and have severe power limitations. It would be highly desirable to replace the commonly used I2C bus with a more power efficient and flexible interface. Similar to smartphones, MIPI I3C could replace digital control signals for smart sensors with in-band interrupts. This would save space on densely populated printed circuit boards (PCBs).
In your opinion, which mobile device functionalities are at the tipping point to evolution? (Historic examples: number locks changed to biometrics, imaging capabilities started going mainstream and so on)
Several applications and functions on mobile devices have the potential to become mainstream. One example is user authentication. Facial/iris recognition on new smartphones has the potential to replace fingerprints. We can also expect a proliferation of displays and touch sensors everywhere to more broadly interact with the physical world, as often is the case starting in smartphones and migrating to other systems like cars or everyday devices in the home.