The original USB standard and connector was designed in 1996 and struggled to gain acceptance until Apple rolled out the connector in its original 1998 iMac. With the USB 2.0 and 3.0 updates, the speeds increased and use of the connector continued to spread, making the “universal” in “universal serial bus” seem prescient. The USB Type-C connector, introduced in August 2014, is already gaining widespread acceptance and is becoming the most rapidly adopted USB standard in history. The big question is: Why? The USB Type-A connector is already in everything from computers to cars, so what makes USB Type-C appealing enough to change the connectors that everyone has been using for a decade? And what are the implications for embedded designers?
The “flip ability” of the connector is the most consumer-friendly attribute of the Type-C connector, but using this connector is more than just saving a few seconds connecting your peripherals and host. This new standard has features and benefits that appeal to a wide variety of user profiles and applications. Some of the key advantages include:
- Ease of use through the unidirectional capability with a common single connector design on either end of the USB cable
- Support for up to 10 Gbps data rates (USB 3.1) while maintaining backwards compatibility to USB 3.0, 2.0 and 1.1
- Ability to provide up to 100 Watts of power through the USB Power Delivery Standard
- Flexibility to support additional protocols (called “alternate modes”) including DisplayPort and MHL
Normally it takes several years for a new standard to gain widespread adoption, especially one that has all these capabilities and a completely new form factor. However, there are major catalysts behind its rapid adoption—most notably, the amazingly fast introduction of mainstream production host products that incorporate the Type-C connector. Even though the Type-C standard just celebrated its first birthday, high profile products such as Apple’s new MacBook and Google’s latest Pixel Chromebook contain this new connector. In the tablet space, Nokia released their N1 product with a single Type-C connector providing data and charging capability. The rapid introduction of these hosts has supercharged the market and the ecosystem, pushing other USB host and peripheral manufacturers to add Type-C connectivity.
Host and peripheral developers are keen to include Type-C connectivity for myriad reasons:
- It differentiates their product — being one of the first allows them to stand out from their competitors.
- It’s easy for end users to grasp the benefits of Type-C (even if it’s only the unidirectional capability) and therefore, easy for manufacturers to justify adding it, replacing older connection standards, and possibly charging more.
- It reduces the number of connectors needed in a product, which reduces the bill of material cost.
- The slim connector form factor enables thinner product designs.
- It’s easy to add initial Type-C functionality to SoCs. For traditional USB 2.0 products, the addition of just two resistors will suffice to gain the connectivity, but of course will not provide many of the other features.
- There are a number of companies offering discrete muxes and crossbar switch discrete components that can quickly convert non-Type-C designs to Type-C (this is how many of the first Type-C products are implemented).
- It’s backward-compatible. Designers can add Type-C to USB 2.0, USB 3.0, and USB 3.1 so manufacturers can phase in Type-C support at the appropriate speed level.
These are key reasons why Type-C will be very popular. Building systems that implement the full Type-C functionality will be a challenge for embedded system designers. While adding USB Type-C capability to an existing USB 2.0 product is fairly simple, adding Power Delivery, USB 3.1 and Alternate Mode support will keep embedded system designers busy for some time. Implementing the full functionality of Type-C, including USB 3.0/3.1, USB power delivery, and alternate video modes such as DisplayPort greatly increases the complexity. Using the traditional OSI architecture model, the Type-C system architecture affects all levels from the PHY to controller to firmware and system software. And crossing all these levels are multiple paths including USB, USB Power Delivery, DisplayPort, DisplayPort Aux, and Type-C channels.
The complexity arises because there are myriad options to implement the various aspects of the embedded design. Should the USB 3.0/3.1 PHYs be separate from the DisplayPort PHY? If they are separate, should a discrete external switch or a carefully designed on-chip switch that doesn’t affect USB or DisplayPort performance be selected? To support USB Power Delivery, is it better to use more costly external components or to redesign a power management IC (PMIC)? Should the Type-C logic be embedded into the SoC or should it be handled by a small microcontroller (MCU) running firmware? For the system software, there is the USB software stack, Type-C software task, Alt Mode software task, DisplayPort software, and DisplayPort AUX software to implement.
During the USB Developers Conference in October 2015, the USB-IF announced new Type-C interface specifications, each of which will help embedded designers incorporate Type-C functionality into their designs. The first, USB Type-C Connector System Software Interface (UCSI), defines the Type-C software interface that is hardware agnostic. The second, USB Type-C Port Controller Interface Specification, defines a standardized register set with an I2C or SPI hardware interface. The third was a Type-C Port Controller (TCPC) that defined the inclusion of the Configuration Channel (CC), Power Delivery (PD) PHY, and PD Controller. And the fourth and final specification was a Type-C Port Manager (TCPM) that defined the SW stack controlling Data Role Swap, Power Role Swap, Alt Mode Discovery, Power Delivery and product specific policies. Standardizing the Type-C hardware and software interfaces will simplify the definition and implementation of Type-C products for embedded designers. Reducing effort for embedded designers means that it’s more likely that successive generations of embedded products will incorporate the Type-C connection.
The rollout of smartphone and tablet designs with only a single Type-C connector for data and power is accelerating. In the consumer product space, digital TV manufacturers are working on adding the Type-C connector to enable communication with future Type-C-connected tablets and smartphones.
As more manufacturers offer products with Type-C connectivity, the virtuous adoption cycle will grow. After the initial phase of first mover and early adopter products, the addition of Type-C to mainstream products becomes a “must–have” for consumers and therefore a check box feature that further increases design-ins. With the increase in volume, there will be a corresponding decrease in Type-C costs, which will spur additional growth. Ultimately, the ability of a single connector to provide data, power, and video with technology based on the world’s most successful wired interconnect standard is what continues to make the USB Type-C connector compelling for consumers and developers alike.
Gervais Fong is a Senior Product Manager for Mixed-Signal PHY IP at Synopsys. Gervais has over 15 years of experience holding product marketing and product management positions covering ASIC, FPGA, EDA, and IP products. Gervais holds a Bachelor of Science degree in Electrical Engineering and Computer Science from the University of California, Berkeley.