Summary of "STM32H5 workshop - 07 I3C interface theory and practice (beginners)"

Summary of STM32H5 Workshop - 07 I3C Interface Theory and Practice (Beginners)

Overview of I3C Interface

I3C (Improved Inter-Integrated Circuit) is a standardized communication protocol designed to overcome limitations of traditional I²C, such as limited speed and the need for external interrupt signals.

I3C maintains compatibility with I²C but introduces new features and naming conventions:

Roles: Controller (instead of Master) and Target (instead of Slave).
Defined by MIPI Alliance’s MPP specification; the basic spec is freely available upon registration.
Uses a two-wire interface (SDA and SCL) similar to I²C but introduces push-pull driving mode after arbitration, enabling higher speeds (up to 12.5 MHz, comparable to full-speed USB).

Key Features of I3C

Push-Pull Driving Mode: Allows faster communication by switching from open-drain to push-pull mode after arbitration. The controller dynamically manages internal pull-up resistors. The clock line is push-pull driven, so clock stretching is not supported.
Dynamic Address Assignment: Targets receive 7-bit addresses dynamically based on unique 64-bit IDs. This supports priority and discovery of devices on the bus.
Common Command Codes (CCC): Standardized commands for common operations reduce the need to study individual sensor datasheets.
In-Band Interrupts: Targets can initiate communication to notify the controller asynchronously and can send payloads with interrupts (e.g., for timing control).
Advanced Features:
- Group addressing (multicast)
- Hot-join mechanism for devices powering up during bus operation
- Secondary controller role switching

Compatibility and Limitations with I²C

Not all I²C devices strictly follow the specification, which may cause issues.
I3C high-speed mode relies on a 50 ns spike filter on the clock line, which may not be present in all I²C slaves.
Clock stretching is disallowed in I3C.
Some addresses are reserved for I3C use.
Legacy I²C mode is supported but with some constraints.
Signal integrity and bus design become more critical at higher speeds.

Advantages of I3C

Higher data rates (up to 12.5 MHz in SDR mode).
Reduced pin count due to in-band interrupts.
Lower power consumption enabled by push-pull mode.
Open standard with freely available basic specification.
Potential for future extensions like multiple data lines and double data rate (not supported on STM32H5 currently).

Practical Demonstration Using STM32H5 and LSM6DSO Sensor

Hardware:

STM32H5 MCU with NUCLEO board and IKS01A3 sensor extension shield (contains LSM6DSO sensor supporting I3C).

Required Modifications:

Remove jumpers to isolate sensors on the bus.
Account for level shifters (1.8V sensors vs 3.3V board), which limit maximum frequency.

Software Setup:

Use STM32CubeIDE and STM32CubeMX for project configuration.
Enable I3C peripheral in controller mode with mixed bus timing to accommodate level shifters.
Configure interrupts and GPIO pins (PB8, PB9 for I3C; PA4 for sensor interrupt).
Use STM32Cube Expansion Package (X-CUBE-MS) for sensor middleware.
Override default I²C functions to support I3C communication.

Demo Behavior:

Successful enumeration of sensor on I3C bus.
Sensor detects vibration (wake-up event) and triggers LED blinking via in-band interrupt.

Code Walkthrough:

Initialization of I3C peripheral and dynamic address assignment.
Handling of enumeration success/failure callbacks.
Read/write register functions implemented using low-level I3C transfers.
Interrupt handling verifies events triggered by sensor activity.

Takeaways

I3C offers significant speed improvements and power savings over I²C.
Its open specification may lead to broader adoption.
Compatibility with I²C devices is mostly maintained but requires careful consideration.
Future enhancements like multi-line data buses and double data rate could further increase throughput.
STM32H5 series supports I3C with embedded pull-ups and push-pull clock driving.
Practical implementation requires some workarounds and careful timing configuration, especially when using level shifters.

Main Speaker / Source

The video is presented by an STM32H5 workshop instructor (likely an STMicroelectronics engineer or technical trainer) who provides both theoretical background and practical hands-on demonstration of the I3C interface using STM32H5 MCU and ST sensor hardware.