Since I2C I3C

Since I2C I3C

Technological artifacts such as old computers are finding their way into museums, but some technologies continue to meet important requirements for computer science.

Within wearable devices, intelligent devices, Robots and computers are called I2C communication bus (Inter Integrated Circuits), dating back to 1982, e SPI (Serial Peripheral Interface), born in 1979.

These buses have driven the short-range communication between circuits and microcontrollers for decades. Now they serve as key interfaces for communication on the sensors of intelligent devices, and wearable computers.

But because the devices are equipped with more powerful sensors and hungriest bandwidth, such as cameras 360 degrees, these obsolete bus will not be able to keep up in the long run. The organization for the definition of MIPI Alliance standards then wants to bury I2C and replace it with the most modern, fast I3C bus and SPI also join the new interface.

The update is analogous to the transition from USB 2.0 a USB 3.0 much faster, even if it took 35 years to go from I2C to I3C.

More sensors are integrated into intelligent devices, robot, drones and industrial devices, and MIPI Alliance states that I3C will act as a short-distance communication channel that absorbs energy.

The I3C will be mainly used for data transfers within a printed circuit board. But as the IoT market expands, serve a growing need to transfer the data collected from a wide range of mechanical sensors, environmental, biometric and health.

Use of I3C could expand to a new range of PC sensors, drones and virtual reality headsets. It could be used for 3D cameras on drones that capture high-resolution images or to speed up communications within the autonomous car.

The new communication bus could also reduce the size of wearable devices, cards and smart devices such as Raspberry Pi. A lot of space is occupied by the I2C bus, UART e SPI su Raspberry Pi, I3C and unite them all in one, which should reduce the number of pins. In addition to saving space, It will also reduce the manufacturing costs of the devices.

Specific support a number of classifications and sensor functions, including accelerometers, touch screen, flight cameras, ultrasonic sensors, transducers and actuators, tactile feedback and infrared or ultraviolet sensors.

MIPI Alliance boasts members such as Google, Intel, AMD, Qualcomm and Sony.

Compared to a typical implementation I2C, I3C the new protocol provides more bandwidth while consuming up to 10 times less energy. The two-wire digital interface supports data transfers 10 Mbps a 39,5 Mbps depending on the mode, to the clock frequency and power consumption levels.

The problem is illustrated in Figure 1, an example of the variety of sensor interfaces used in typical multi-sensor systems.

FIGURE 1 A sensor system based on multiple interfaces (Source: MIPI Alliance)

The MIPI Alliance has released for I3C, a specification that incorporates the I2C and SPI attributes, as an alternative interface that includes the advantages of these interfaces into a single interface. By using I3C, system designers can easily connect multiple sensors, while reducing the energy consumption, the components and implementation costs. The figure 2 shows a sensor system based on I3C sample.

FIGURE 2 A sensor system based on I3C I3C that uses a bus (source: MIPI Alliance)

A pure I3C bus supports HDR mode and double speed, support multi-master, dynamic addressing, compatibility with command code and a uniform approach to advanced power management, as the sleep mode.

Configuring the bus I3C and roles of the device

The I3C standard defines five roles for devices:

  • Main master, I3C which controls the bus and the function, and it includes control of the bus ownership and transfer to the secondary master.

  • The secondary master, which takes temporary control of the bus I3C, It requires authorization from the main master and passes control to the main master once the control activities.

  • Slave, who answers to common or individual commands from master I3C.

  • Slave peer-to-peer, which can be written or read by another slave without the master of interaction.

  • I2C slave, I2C for legacy devices present in a bus I3C, I3C to which the master devices can communicate but with speed and limited capacity.

MIPI Specifications I3C define different responsibilities for each type of device, such as arbitration SDA management, the dynamic assignment of addresses, the hot-join features, the ability HDR master and slave.

  • The SDA arbitration solves the bus properties when multiple devices transmit simultaneously. I3C uses the SDA line during the arbitration process and follows the open-drain common approach. The master manages typically arbitration SDA.

  • Dynamic Address assignment: I3C the primary master assigns each device a unique address, when the bus is initialized or when a new device is connected to a bus configured I3C.

  • Quick union function: the slaves must not be activated when the bus is turned on and I3C could be connected but not activated or added later. The activation of these slaves is known as hot-join and enables the master to assign a dynamic address to the slave when it requires a.

  • Capacity master and slave HDR: master and slave can support high data rates 16,84 bit / s and over are defined as master / slave HDR.

It offers developers an unprecedented opportunity to create innovative designs for any mobile product, smartphones, to wearable devices, to safety systems in cars.

The technology is implemented on an I / O CMOS standard.

The specific I3C is quite recently was released early 2017 and it promises a consistent way to interface with the sensors that will reduce the difficulties in the use, Today they could use UART, SPI I2C. In 2013, the MIPI Alliance began work on a common standard of sensors that would keep the best features of I2C and SPI, but added features that improve the integration of the sensor. In addition to providing a common standard by which to draw, the overall benefits of I3C compared to I2C and SPI include lower deployment costs; I3C requires very little space within the sensors themselves. I3C also offers higher communication speed and a lower power consumption; the whole

maintaining backward compatibility with I2C. According to the MIPI Alliance, “The standard sensor interface MIPI I3C is a turning point for the integrated sensor systems. It built a superset of features in addition to I2C (two-wire) with additional existing data in high-speed mode capable of satisfying the cases of use of sensors that currently require an SPI bus (four-wire).

I2C is created for the first time by Philips (ora NXP) in 1982. For microcontrollers (MCU), I2C is often used to manage the General Purpose I / O (GPIO) When all the pins have been used on other things. However, I2C had no significant updates for over two decades and, with so many sensors in use today for the Internet of Things applications (IoT), it is understandable that I3C was expected.

FIGURE 3 Comparison between I3C and I2C: consumption of energy and bit rate. (Source: MIPI Alliance).

I3C works well for everything that historically has used UART, SPI or I2C and will be used to connect many components such as sensors, display, always active cameras (low resolution), controller, capacitive sensors, mobile applications, transducers, acoustics, and other peripherals. I3C will keep the interface 2 wires present in I2C. I3C deals with some historians with I2C critical points that have to do with in-band interrupt, dynamic addressing, management of multi-master and standardization of common commands with command codes. I problemi con hot-join, error detection and error recovery with I2C were also resolved in I3C. I3C has also reduced the energy consumption while providing data transmission speeds in excess of 12,5 MHz compared to 400 kHz I2C.

TABLE 1: The interface of the I3C MIPI sensor supports several new features that improve the integration of the sensor. (Source: MIPI Alliance).

Bus simplified data with the new specification I3C

I3C is developed by the alliance MIPI (Mobile Industry Processor Interface) and it is specifically intended to meet the interconnection requirements to future-proof in mobile devices, Internet of Things and wearable computing devices incorporating an increasing number of advanced sensors and peripherals.

The specific MIPI I3C combines the I2C and SPI functionality into a new unified standard and scalable interface to connect together multiple devices in embedded systems, with a minimum of use pin, new features and improvements in power management and data speed.

The sensor working group MIPI, It composed of many of the leading manufacturers of systems and ASIC suppliers, jointly it defined the specific I3C, in order to reuse existing interfaces as much as possible by reducing the number of pins, providing in-band interrupt, reducing power use and design costs, and increased bandwidth.

I3C develops new features on mature standard I2C, as a new data transmission high-speed mode capable of supporting a lot of data from sensors or other peripheral devices, as well as better support for relatively large networks of many devices connected to a host microcontroller.

Furthermore, I3C can compete with serial interfaces like SPI embedded broadband, but still uses only two wires as I2C ago. The I3C standard is backward compatible with I2C, then legacy devices with I2C interfaces can connect to the bus I3C, However, a new hardware is needed (both on the device that on the side of the host controller) to fully utilize the bandwidth and provides other benefits that I3C.

I3C provides faster speeds, greater energy efficiency, a reduced pin count compared to networks SPI multi-device and support for relatively large suite of sensors connected to a host microcontroller using only two strands but carrying increasing amounts of rich data sensors in the wireless sensor network and IoT applications.

I3C has been developed by Sensor Working Group of MIPI as a potential way to unify the panorama of the serial bus with a single coherent interface can handle any type of device, allowing all types of sensors to be easily integrated into embedded systems.

Its purpose is to combine the simplicity and the low number of wires I2C with high speed and energy efficiency of SPI, to combine both of these popular standards along and add powerful new features such as interrupt support in-band without the need for additional cables interrupt, advanced power management and dynamic routing of individual chips on the bus. I3C It does all this while maintaining largely backward compatibility with existing devices I2C.

A typical smartphones today can contain up to a dozen sensors, and widespread adoption of technologies and the reduction of costs as MEMS sensors means that these data are producing much more complex and rich.

Move all these data on the central controller it is extending the capabilities of today's familiar interfaces like SPI or I2C, and this is the problem that I3C is designed primarily to solve. I3C aims to incorporate and unify the key attributes of I2C and SPI while improving the capabilities and performance of each approach with an interface and comprehensive and scalable architecture.

A typical system in use today can use a combination of I2C and SPI devices, with three wires for SPI, two wires for I2C, another wire for each selection line of the SPI device, plus an interrupt line for each peripheral device.

This complexity is rapidly adds to modern sensors and I3C suite aims to replace a dozen or more wires with only two wires, providing interrupt functionality band without any need for dedicated interrupt lines connected to the host device, reducing fragmentation between these different standards in the device market, releasing pin on the host device, simplifying the engineering of PCBs and making smaller devices, as well as offering speeds of up to 27 megabits per second.

I3C also includes the multi-master support: this means that allows devices on the bus to request the master role, Therefore, the bus architecture is not limited to a single fixed master device and to a number of slave devices.

The devices can be both master and slave and direct communication “peer-to-peer” I3C between the devices on the bus is possible without causing the master device should be involved in this exchange. I3C also introduces dynamic addressing, hot-join and a uniform approach for advanced power management, such as sleep mode.

The devices on the bus can be switched on and off and should not be activated when the bus is turned on I3C. They can be added on the bus at a later time or initially linked but not lit, no bus loading issues.

This hot-join features, as with USB devices, allowing the master device to assign a dynamic address to the slave device when it arrives on the bus, and it has advantages for energy efficiency when the sensor and peripherals are switched on and off to save power, in addition to allowing removable modules and hot-swappable.

The dynamic address configuration means that the master device on the bus assigns each device a unique address, when the bus is initialized or when a new device is connected to a I3C already configured bus. As the dynamic host configuration now ubiquitous in IP networks, This address autoconfiguration makes the hardware configuration potentially much simpler I3C, eliminating conflicts between hardware devices with fixed addresses.

4 replies
  1. Amilcare
    Amilcare says:

    This system was designed for communication between the ic present in the same tab.
    How do I know if in the same room does not have a problem.
    Go over in theory you can but you have to sacrifice speed and increase consumption.
    In fact you need to reduce the resistance of pull-up in a manner that any disturbances are little influential.
    By contrast a decrease of such resistance involves a greater effort of the various IC to bring the lines of communication at a low level and consequently a lower speed, therefore lesser frequency of communication between the various devices or IC.

    • Avatar
      D80 says:

      what affects a lot also about communication, in addition to the physical characteristics of the line and the installation ambient conditions ( any electromagnetic fields that may cause effects of mutual induction, parasitic capacitances with surfaces to potential and different frequencies etc.) It is the supply filtering of the various devices, I do not know how or why but it is a fact that if you use a power supply switching that does not have well-filtered output for powering of devices , disorders also interfere negatively on the communication protocol making unreadable the data transported, sometimes it just turns on an electronic device in the same room to corrupt data, ( just a Chinese energy-saving bulb )

      from what I have seen with a practice test, you can not go beyond the 5 m using all due caution and with appropriate shielding, reducing the frequency to a minimum etc. , which it has made me realize that the i2c protocol can be used safely between devices within the same machine or within 5m in the same structure,However, it could obviate the problem of maximum distance using the optical fiber, making the communication line immune to external agents… the problem, however, begins to move on the income side…. worth?

  2. Avatar
    McFly77 says:

    salve, I looked around a bit but have not yet succeeded in finding an answer…
    utilizzanto I2C to connect the sensors (temperature / humidity / pressure) on a system based on Arduino, what is the maximum length of “loop” cable that “turn” for the various sensors?

    thank you!

    • Just4Fun
      Just4Fun says:

      The limiting factor is the maximum capacity. The specifications indicate up to 400pF.
      Using the slower speed (100kHz) and assuming 50pFdi various parasitic capacitances, They will remain approximately 350pF.
      Assuming for a 20pF / 30cm wire will reach a maximum. The 525cm. I'd keep me no later than the 2/3 meters, always at minimum speed (100kHz). As usual an oscilloscope is a must for the checks in a specific case.

      For more info see this document and specifications and recommendations for I2C bus:


Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply