Conquering the Timing Challenges in I3C communication with Prodigy’s Solutions!

One of the primary challenges in designing I3C Protocol communication is the occurrence of timing issues, which can cause communication errors. This will be challenging to debug for the engineers.  To address this, Prodigy Technovations Pvt. Ltd (Prodigy) provides an I3C Protocol Analyzer and Exerciser that provide precise timing analysis for reliable communication.

The timing and plot diagrams of the I3C Protocol Analyzer assist engineers in identifying the root cause of timing problems like inconsistent clock rates (or) timing mismatch. By analyzing the information, developers can fine-tune their designs to meet I3C timing specifications, ensuring accurate and error-free communication. Below is the snapshot of the timing measurement using the I3C Protocol Analyzer.

Figure 1: Accurate timing measurement of clock and data Signals of I3C Bus

During testing, most of the test cases will be related to data loss and protocol non-compliance in corner cases. These are intermittent problems difficult to acquire in test equipment.  Prodigy Technovations make I3C tester solutions that address these issues by continuously capturing and analyzing I3C protocol data and streaming it into the host computer storage system.

The PGY-I3C-EX-PD, Prodigy’s I3C Protocol Analyzer and Exerciser, supports continuous streaming of protocol activity to the host computer. It can generate and capture a vast amount of protocol traffic on the I3C bus using its substantial memory buffer. By analyzing the captured signals, Prodigy’s solution can detect timing violations, such as NACK responses from slave devices, and highlight the same in the report assisting engineers in real-time in solving the potential problems.

Below are the snapshots of Data representation with a waveform view of signals and report that shows errors.

Figure 2: Plot view with Clock and Data representation along with the result windows

Figure 3: Report generation sample with a data parity(S2) error

Interoperability issues due to timing mismatches can also hinder I3C testing. Prodigy’s solution plays a crucial role in resolving these issues efficiently. During the design cycle, interoperability testing is vital to ensure seamless functionality between devices from various vendors. Prodigy supports the defined MIPI standard Conformance Test, including the I3C Conformance Test Suite (CTS v1.1), enabling engineers to validate timing constraints and guarantee interoperability across devices.

The test engineers can perform regression testing using Prodigy’s API in Python / C++ for hours and analyze the captured I3C bus signals. This feature enables us to identify and address the issues that can occur randomly.

By combining these features, Prodigy offers a comprehensive solution to the timing challenges in I3C testing. It ensures precise timing analysis, optimizes clock rates, captures, and analyses signals to prevent data loss and protocol violations, validates timing constraints, and resolves interoperability issues efficiently.  Moreover, the feature of the solution is available in the same GUI software and the user can navigate between windows easily.

In conclusion, with the features and user-friendly software, the engineers can reduce their testing time (that might take days to weeks for complex issues) to meet their tight project schedule. It also ensures the quality of the product’s compliance with I3C bus standards that avoids post issues/failures in the field and leads to their end customer’s satisfaction.

Prodigy Technovations has been working on I3C technology since its inception. We have developed many technical contents to support our customers in developing and deploying I3C in many different applications.

Our I3C debugging solutions:

1. I3C Protocol Analyzer and Exerciser
2. I3C Electrical Validation Software
3. I3C Protocol Decode Software
4. Logic Analyzer for Embedded Interfaces

Introduction to I2C Protocol:

I2C stands for Inter-Integrated circuit. It can also be referred to as IIC or I2C. I2C Protocol is a serial communication protocol, and it is widely used for short-distance communication. It provides simple and robust communication between the Peripheral device and the microcontroller.

I2C Protocol consists of two wires SDA and SCL which is bidirectional synchronous serial bus communication. Thus, I2C Protocol takes two wires for communication which also translates to low cost and this low cost has made I2C Protocol the most commonly used Serial Bus across most applications including IoT, consumer electronics, automotive, aerospace, and industrial equipment.

I2C Protocol is a synchronous protocol that allows a master to initiate communication with a slave device. I2C protocol is a master-slave communication where the master provides the clock which becomes the data transfer rate or clock frequency. It is a bi-directional bus meaning the master can write to the slave and read from the slave it is a serial bus which means data is a clock and it is shifted bit by bit and there are two bus lines serial clock (SCL) and serial data (SDA).

As u see in the diagram three slaves are connected to the same I2C Master and there is two pull-up resistor which is required for the I2C device to communicate properly this is because the I2C protocol works on the SCL and SDA bus lines which are an open drain or open collector the transmitting device just lets go of the I2C bus to create logic one and pulls or drives the line the ground to create logic 0.

In I2C Protocol there are 5-speed categories including standard mode, fast mode, fast plus mode, high-speed mode, and ultra speed mode these speed categories range from 100 kHz to 5MHz, where standard mode is 100KHz, Fast mode is 400KHz, Fast mode plus is 1MHz, High-Speed Mode is 3.4MHz and Ultra-fast mode is 5MHz. 100KHz up to 1MHz are very similar, while 3.4 MHz needs some special consideration, and 5MHz being unidirectional requires even more special attention. But the most common speed categories for I2C Protocol are Standard mode, Fast Mode, and Fast mode plus these modes are easy to implement.

I2C Protocol transactions are initiated with a start condition, the start condition is defined as the master driving SDA line low while SCL remains high, and note that it must be initiated with the I2C bus in an idle state means SDA and SCL lines are both high.

The slave address immediately follows the start condition, and it will be 7 bits or 10 bits long it should be noted that each device on the I2C bus needs a unique slave address. Next is the read-and-write bit, which immediately follows the slave’s address, this bit informs the slave if the master wants to read or write. 1 indicates the master wants to read from the slave and 0 indicates the master wants to write.

The next section is the Acknowledge bit and we can think of ack bits like a handshake between the master and slave and they occur on every 9^th clock cycle, if ACK is 0 then data can be transmitted, and if ACK is 1 data cannot be sent. Next is the data byte which contains the information being transferred between the master and slave, It contains 8 bits of data.

The last section of the I2C protocol is the Stop condition all I2C transactions should be terminated with a stop condition, the stop condition is defined as the master releasing the line while the SCL signal level is high after a stop condition the I2C bus will remain in idle state and won’t be free for the next I2C transaction.

There are two important concepts of I2C Protocol: I2C Arbitration and I2C Clock Stretching

I2C Arbitration: I2C Protocol is a multi-master bus it can be possible that multiple masters are driving the bus simultaneously, If one of them detects SDA is low when it should be high, it assumes that another master is active and immediately stop its transfer.

I2C Clock Stretching: The master wants to send the data where the slave is not ready to receive data so the  I2c slave pulls the SCL line low.

Advantages:

• I2C Protocol supports multi-master, multi-slave communication
• It uses only two wires
• In I2C Protocol ACK/NACK functions can be proved useful for error handling
• Adaptable as it can adapt to the needs of various slave device
• In I2C Protocol the addressing is very simple and does not need any CS lines to add extra devices like SPI Protocol
• It uses flow control

Disadvantages:

• I2C Protocol is a half-duplex mode of communication
• The hardware complexity increases when the number of master/slave devices is more in the circuit
• Many devices have multiple addresses stored which can cause conflicts

Applications of I2C Protocol:

• Accessing DACs and ADCs
• Reading certain memory ICs
• Reading hardware sensors
• Communicating with multiple micro-controller
• Transmitting and controlling user-directed actions

Debug I2C Protocol:

Prodigy also offers an I2C Protocol analyzer to capture and decode the I2C packets. The I2C protocol analyzer has the advanced capability not only to trigger but long allow very long captures which is very useful for the embedded design engineer during the debugging.

Prodigy I2C Protocol Analyzer

About the Author

Sensor Challenges in Next Generation Consumer Devices, IOT, and Automotive Design.

Over the last decade, we have seen an explosion of mobile phone devices along with sensors on the devices. Right from accelerometers, gyroscopes, ambient light, proximity, infrared, humidity, and temperature. These sensors are great for the consumer experience from the system integration poses a challenge. Consumers are demanding every device to be as smart as a smartphone. Hence the demand for sensor integration into consumer devices has grown exponentially. Each of these sensors requires an interrupt and hence dedicated GPIO pins are taken away from the system designer.

In case the system or 15 Sensors, 15 pins of the chip need to be dedicated to the sensors interface only. Adding to the challenge is the kind of functionality sensors manufacturers are adding to the sensors. Modern-day sensors require higher bandwidth for data transfers.

To the rescue comes I3C Protocol Analyzer. I3C Protocol Analyzer is a MIPI standard supporting inband interrupts. Its backward compatibility with I2C, SPI, and inband interrupt saves the dedicated GPIO pin for the system designer. However, as the number of sensors added to consumer device increases. The Debug of the sensor is a new challenge during the board bring-up or Firmware Debug. There is a need to not only understand which sensor interface is misbehaving it’s also required to know the sequence of the transaction.I3C also supports dynamic addressing with devices needing to enumerate and assign addresses. This increases the need for advanced debugging and analysis of the protocol. The engineers need to be equipped to handle the new complexity added new I3C MIPI standard.

If you need help with I3C Debug and I3C Protocol Analysis, Prodigy is here to help. Prodigy offers I3C Protocol Analyzer and Exerciser. Prodigy is a very active contributor to the MIPI Alliance and the MIPI Sensor Workgroup, making contributions to the specifications such as I3C, MIPI PHYs, CSI, DSI, UniPro, and more.

What is MIPI I3C?

The MIPI I3C Bus interface is an evolutionary specification that builds upon the legacy I2C standard. The aim is to reduce the number of physical pins used in sensor system integration and supports low-power, high-speed digital communication typically associated with UART and SPI interfaces so that I3C becomes a single interface combining all the capabilities of the legacy interfaces.

I3C Protocol has a multi-drop bus which, at 12.5 MHz, is over 12 times faster than what I2C supports while using significantly less power.

I3C Protocol’s main features include:

• Backward compatibility with legacy I2C
• Multi-Master and Multi-drop capabilities
• Dynamic Addressing
• In-Band Interrupts
• Hot-Join support

The I3C Protocol interface is expected to play a fundamental role in streamlining sensor integration in smartphones, Internet-of-Things (IoT) devices, and wearables. I3C can also be used to manage complex systems as and when designers migrate to a common management transport which drastically reduces cost and latency in such complex systems while also enabling new capabilities.

MIPI I3C Theory of Operations: I3C Protocol

All I3C Protocol communications occur within a frame. The frame begins with a START, followed by one or more transfers, and a STOP.
The I3C interface supports Single Data Rate (SDR) messages which are similar to I2C Messages. The maximum clock speed is 12.5MHz. It also supports high data rate (HDR) messages. In HDR, data transfer is equivalent to clock cycles. There are two types of messages Broadcast and Direct common command code (CCC) messages which allows the master to communicate with all or specific slave on the bus.
I3C protocol is based on the frame encapsulation approach. The I3C frame always includes START, the Header, the data, and the STOP. The I3C bus is always initialized in SDR mode and never in HDR mode.
Common Command Code (CCC) commands protocol is formatted using only SDR. CCC is transmitted to specific to slaves or all slaves in the I3C bus. CCC General format is shown in this figure.

For the HDR modes:

• First the dedicated Broadcast I3C address(7’h7E) is issued to all slaves on the I3C bus.
• Then one of the Enter HDR CCCs is issued, indicating that the Master is entering the HDR mode. Each HDR mode has its own Enter HDR CCC.
• This is followed by one or more HDR transfers.
• HDR mode is ended by using the HDR exit pattern protocol.

For more details on I3C protocols, please refer to MIPI® I3C specifications.
I3C devices have Bus and Device characteristic registers which will hold information about the capabilities of I3C devices.
I3C bus can be configured with multiple devices. These devices are I3C Main Master, I3C Secondary Master, I3C Slave, and I2C Slave.

I3C devices may have many features appropriate for their function in the I3C bus. Depending on the I3C Bus system’s need, it may not be necessary that all features are enabled for any particular bus instantiation. Enabled features of every I3C device shall be described in the characteristic register of the device. Master obtains the characteristic register info during the power-up state of the I3C bus.

At the start-up stage from power-down, the main master shall assign a unique dynamic address to every device on the bus including itself. Dynamic address creates a priority ranking of device interrupts. If any secondary master present in the I3C bus shall be made aware of dynamic address and characteristic registers.

I3C-based electronic hardware design involves the design of I3C Master, I3C Slave, and I3C system designs. These designs offer different challenges at different stages of the design cycle. Design engineers need a tool to debug the I3C device for reliable operations. Some of the important requirements are

• Designers who are developing master or slave, need a fully working Master or Slave device which designers can configure and test their designs.
• Make sure I2C devices can co-exist with I3C bus
• They need a tool that will capture the communication between Master and slave and analyze the protocol traffic for protocol errors
• Need a tool to capture protocol traffic at a specific event. These events could be anticipated error conditions or protocol activity
• Emulate the I3C bus using the designed Master or Slave device in the I3C network

Where is I3C Protocol being used?

I3C protocol is used as a de-facto standard for integrating sensors in the System. Temperature sensors, gyroscopes, etc. There are new interesting applications for I3C interfaces in data centers as management buses.

Debugging I3C Tools :

When working with I3C, it is important to have the right set of tools to ensure the I3C design is implemented properly. Having a logic analyzer and oscilloscope is always helpful to debug complex hardware timing issues. There are cheaper tools available in the market to test I3C, however, limited in capability.

A logic analyzer is an excellent tool to debug when implementing and designing the I3C Bus. This can help you understand the protocol packet-level issues.

An oscilloscope is helpful in case you want to measure the timing parameters of the I3C Device.

I3C protocol analyzer can be very helpful to do I3C packet sniffing. Prodigy Technovations also offers an I3C Electrical Validation, and I3C Protocol Decode Software to debug your I3C packets using a Tektronix oscilloscope.

How does Prodigy Technovations Interfaces with I3C?

Prodigy Technovations has several different tools that interface with the I3C protocol. All the I3C tools fall into two different areas. The protocol analyzer monitors the traffic that is happening on the bus. The exerciser allows users to interface directly with I3C System and drive I3C Data.

Benefits of Prodigy’s I3C Protocol Exerciser and Analyzer:

• Ability to configure it as Master or Slave
• Ability to configure PID, BCR, and DCR registers
• Supports legacy I2C slaves and Master
• Generate different I3C and I2C SDR and HDR Packets
• Flexibility to upgrade the unit TSP and TSL encoding (When it is available)
• Error Injection such as CRC errors, parity errors, and ACK/NACK errors
• Variable I3C data speeds
• Simultaneously generate I3C traffic and Protocol decode of the Bus
• Timing diagram of Protocol decoded bus
• Listing view of Protocol activity
• Error Analysis in Protocol Decode
• State Machine view of the I3C packets
• Ability to write exerciser script to combine multiple data frame generation at different data speeds
• USB2/3 host computer interface
• Flexibility to upgrade to the unit for evolving I3C Specification

I3C Test Setup