The Tech Blog

I3C is one of the newer standards in the wired domain and yes, the name is deliberately similar to I2C. It’s called “Improved Inter-Integrated Circuit”. Developed by the MIPI Alliance as an evolution of the older I2C protocol, it addresses some of the limitations of I2C, like its restricted speed. Just a heads-up: it’s pronounced ‘eye-three-see,’ not “eye-cubed-see,” unlike how I2C is pronounced “eye-squared-see.”

I3C still uses the familiar two-wire interface (SDA and SCL) but has enhanced features. SDA carries data and SCL the clock. I3C introduces dynamic address assignment, where devices can be automatically assigned addresses without manual configuration. Additionally, it supports hot-join, allowing devices to join the bus after initialization without disrupting communication which is a big feature upgrade from I2C. In-Band-Interrupts is a new feature that allows the slave devices to generate interrupts without requiring an external signal. In I2C master usually polls the slaves for info or the slave pings the master via a separate line. I3C can theoretically now reach a speed of 33Mbps compared to 3Mbps in the latest I2C HS mode which is coming close to the SPI realm of things. I3C handles this by reducing the bus capacitance limit to 50pF from 400pF on I2C. It supports lower voltage levels like 1.2V and 1.8V. Also, you don’t need external resistors as it’s built-in.

Why does it matter? The new protocol provides a standardized method for connecting multiple sensors to an SoC using just two lines. Imagine IoT sensors all utilizing a common 2-line protocol – it greatly simplifies layout and connections. It’s designed to address the need for higher speeds in connecting multiple sensors within mobile devices. I3C offers a future-proof solution that retains the simplicity of I2C while enhancing performance.

It’s still early days for this protocol. Currently, only a limited number of SoCs and sensor modules support it. I expect a gradual adoption over the next few years. Personally, I wouldn’t recommend using it in projects unless there’s a compelling reason to do so.

Today let’s talk about a technology we all interact with almost daily: HDMI. It stands for High-Definition Multimedia Interface and is currently the defacto digital interface for transmitting video and audio signals in a single cable. HDMI was first introduced in 2002 as an alternative to a popular standard at the time called DVI(Digital Visual Interface). It was developed by a group of companies including Sony, Philips, Toshiba, and Hitachi. The HDMI’s first version in 2002 supported 1080p video and 8-channel audio with 4.95Gbps bandwidth. The latest version(v2.1b) supports 8k@60fps and 4k@120fps with a bandwidth of 48Gbps.

Let’s discuss the electrical side.

An HDMI connector consists of 19 pins.
TMDS (Transition Minimized Differential Signaling) Channels (Pins 1-3, 7-9, 13-15): These are the three(D+, D- & Shield) pairs of main channels that carry video and audio data using differential signalling.
Clock(Pins 10-12): TMDS differential clock for synchronization between systems
CEC (Consumer Electronics Control) (Pin 13): This channel allows devices to send control commands to each other, like turning on your TV with your set-top box.
DDC (Display Data Channel) (Pins 15-16): Used for communication between the source and display. It’s I2C based. The display uses it to tell the source what modes/formats it supports.
Hot Plug Detect(Pin 19): Signals the source device when a display is connected/disconnected.

On the physical connector design side, there are 3 main versions. Type A Standard is the most common and biggest one, Type C Mini and Type D Micro are other smaller space-constrained versions. Pin count-wise all are the same except for size reduction. From the PCB routing POV, all the high-speed 4 differential pairs of TMDS signals are to be routed with a single-ended impedance of 50Ω and differential impedance of 100Ω.

HDMI has undoubtedly transformed how we connect our devices over the years. Personally, though I think, its future might be limited, especially with USB Type-C now supporting HDMI signals through Alternate Mode. Probably a decade away from USB Type-C becoming the universal connector for everything.