The MIPI I3C Host Controller Interface (MIPI I3C HCI℠) specification defines an interface that operating systems use to accessMIPI I3C®devices and capabilities. It delivers crucially needed efficiency for designers of smartphones, computers, Internet of Things (IoT) devices, automotive systems and other applications that leverage the scalable, low-power, medium-speed, two-wire I3C utility and control bus interface.
MIPI I3C and MIPI I3C Basic℠ (the publicly available subset version of the specification) are used for connecting peripherals to application processors. The unifying I3C bus interface can connect multiple peripheral devices from various vendors to an application processor, streamlining integration and improving cost efficiencies.
With MIPI I3C HCI, application processor vendors benefit from a consistent method for interfacing to MIPI I3C, eliminating the need for product-specific I3C drivers. Instead, operating-system vendors, developers and distributors can offer generic I3C drivers that are portable across hardware platforms, helping to control cost and complexity, and freeing designers to focus their efforts on developing applications rather than interfaces. This allows vendors and developers to easily and efficiently integrate support for I3C, for applications that go beyond simple sensor devices.
MIPI I3C HCI defines a common set of capabilities for the host controller and the software interface, allowing for the building of class definitions based on a common set of features. The definition allows for vendor-specific extensions and optimizations.
The specification defines several optimizations based on typical usage. For example, the combo command feature allows for the efficient one-shot transfer of write and then read transfers on the bus.
The current version of MIPI I3C HCI, version 1.1, aligns with the latest I3C advances by enhancing existing features and adding new capabilities. Key features include:
Support for MIPI I3C primary controller operation on the I3C bus
Two modes of operation: programmable input/output (PIO) mode, delivering direct data interface support with programmable buffer depths for the transmit/response and data buffer, and direct memory access (DMA) mode, providing interface support for scatter gather transfers for data buffers
Power-efficient operation of the host controller, which helps maximize battery life in mobile devices
Support for I3C data rates, including I2C fast mode (up to 400Kbps), I2C fast mode+ (up to 1Mbps), I3C SDR (up to 12.5Mbps) and optional I3C HDR Modes (for faster transfers)
Support for extended capabilities, including vendor-specific ones, to enable more sophisticated hardware or additional functionality
Group addressing, which enables multicast-type addresses to be assigned to multiple peripheral devices
Defining bytes for common command codes (CCCs), extending greater flexibility to create additional CCCs or augment the existing CCCs defined in I3C
Scatter gather for ring pointer, flow control, PIO/DMA mode indicator, ring full indication and other features for improved performance in DMA mode
MIPI I3C HCI is also included in theMIPI Touchfamily of specifications, making it possible to use touch commands and multiple data streams to add differentiating touch features to a design. Application processor companies can apply the specification to standardize the HCI method used in their devices.
MIPI Alliance welcomes contributions to the specification. If you would like to contribute, please contact the MIPI Software Working Group firstname.lastname@example.org.