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Six Key Issues When Designing USB Protocol Interfaces

Posted by: Yoyokuo 2022-05-03 Comments Off on Six Key Issues When Designing USB Protocol Interfaces

Designing a system that uses high-speed signals for data transmission can sometimes be difficult, especially when there are so many communication protocols to choose from. . While many communication protocols are ideal for high-speed signals, one protocol that is particularly popular is the USB protocol. It is often associated with gaming, car audio head units, PC and laptop applications. The USB protocol has become a more general high-speed data protocol, interface, and cable specification due to its support for multiple types of data transfer and high-power charging. Figure 1 shows the evolution of USB since its release in 1998.

Designing a system that uses high-speed signals for data transmission can sometimes be difficult, especially when there are so many communication protocols to choose from. . While many communication protocols are ideal for high-speed signals, one protocol that is particularly popular is the USB protocol. It is often associated with gaming, car audio head units, PC and laptop applications. The USB protocol has become a more general high-speed data protocol, interface, and cable specification due to its support for multiple types of data transfer and high-power charging. Figure 1 shows the evolution of USB since its release in 1998.

Six Key Issues When Designing USB Protocol Interfaces

Figure 1: The evolution of the USB protocol – USB 4.0 released in 2019

To give you an idea of ​​whether the USB protocol is right for your system and meet your high-speed interface needs, we’ve listed six key questions that designers typically need to consider:

1. What is the interface function of your CPU or MCU?

When using USB, the central processing unit (CPU) or microcontroller (MCU) interface capability is the first consideration, as this device is the basis for high-speed data transfer in your design. If you find that you need to transfer data from the CPU or MCU to an attached peripheral with data transfer rates greater than 10 Mbps, USB is a good choice.

2. How do you transmit data over long distances when the interface’s data link lacks reliability?

USB can replace this connection with existing integrated circuit solutions, thereby extending the communication capabilities of the interface. USB redrivers help maintain signal integrity over long distances. Devices like the TUSB216 (USB 2.0) and TUSB1002A (USB 3.0) have USB protocol-specific features that simplify the implementation of redrivers in USB.

3. What if your MCU or CPU has only one instance of the USB interface?

USB includes a device called a USB hub that easily converts one port into multiple ports. Four-port high-speed USB hubs such as the TUSB4041I, TUSB8041A, and TUSB8042A help increase the number of devices that can be used simultaneously.

4. What if your CPU or MCU interface has limited interface options?

USB solutions have advanced to convert to other interfaces such as Universal Asynchronous Receiver Transmitter (UART) or Serial Advanced Technology Attachment (SATA). The USB bridge can support USB to UART and SATA conversion. If your MCU or CPU does not have an interface connected to UART or SATA, or the transmission distance is too far for a normal UART or SATA interface, consider using a USB bridge like TUSB3410 and TUSB9261.

5. Do all USB connections require external connections?

While external USB ports are found everywhere in consumer electronics, the USB connection doesn’t have to be external. If the MCU or CPU you choose has USB capabilities, you can also consider using USB for embedded connections to other MCUs or CPUs in the system. USB has built-in data encoding to reduce EMI and link power management for high power efficiency. USB also adds flexibility to client software with many low-level drivers.

6. What if you need more flexibility than a standard USB connection can provide?

USB Type-C®The emergence of the protocol has greatly improved the flexibility of USB. USB Type-C can create a peripheral that acts as a USB host or USB device, allowing the system to react to different types of connections in a variety of ways. The USB Type-C active multiplexer also ensures that the interface is configured correctly while providing USB-compliant signal integrity.

Active multiplexers such as the TUSB542 and TUSB1042I should be used in your standard Type-C designs. USB Type-C also facilitates the transfer of multiple types of high-speed data over the same interface, such as DisplayPort, HD Multimedia Interface, UART, and other video or custom interfaces. The TUSB1146 and TUSB1064 are essential for the system to enable its Alternate Mode feature.

For technical details on the USB protocol and USB implementation, check out the resources below. If you’re having trouble with USB technology and need help choosing the right product for your system, it’s available at TI E2ETMPost exchange on the interface forum.

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