It is sometimes difficult to design a system that uses high-speed signals for data transmission, especially when there are many communication protocols to choose from. While many communication protocols are ideal for high-speed signals, one is particularly popular: THE USB protocol. It is often associated with games, car audio consoles, PC, and laptop applications. The USB protocol has become a more general specification for high-speed data protocols, interfaces, and cables due to its support for multiple types of data transfer and high power charging. Figure 1 shows the evolution of USB since its launch in 1998.
6 Key Problems In Designing USB Protocol Interface
To give you an idea of whether the USB protocol is a good fit for your system and meets your high-speed interface needs, we’ve listed six key questions that designers generally need to consider:
1. What is the interface function of your CPU or MCU?
When using USB, the interface capabilities of the central processing unit (CPU) or microcontroller (MCU) need to be considered first, as this device is the foundation of your design for high-speed data transfer. USB is a good choice if you find that you need to transfer data from the CPU or MCU to connected peripherals at rates greater than 10 Mbps.
2. How do you transmit data over long distances when the data link of the interface lacks reliability?
USB can replace this connection with an existing integrated circuit solution, extending the communication capabilities of the interface. USB adapter drives help maintain signal integrity over long distances. Devices like TUSB216 (USB 2.0) and TUSB1002A (USB 3.0) have USB-protocol-specific features that simplify the implementation of converter drives in USB.
3. What if your MCU or CPU only has one instance of a USB interface?
USB includes a device called a USB hub that can easily convert one port into multiple ports. Four-port high-speed USB hubs such as TUSB4041I, TUSB8041A, and TUSB8042A help increase the number of devices that can be used at the same time.
4. What if your CPU or MCU interface has limited interface options?
Advances have been made in USB solutions that can be converted to other interfaces, such as universal Asynchronous transceivers (UART) or Serial Advanced Technology Accessories (SATA). USB bridge supports CONVERSION from USB to UART and SATA. If your MCU or CPU is not connected to a UART or SATA port, or if the transfer distance is too far for a normal UART or SATA port, consider using a USB bridge-like TUSB3410 and TUSB9261.
5. Do all USB connections require an external connection?
While external USB ports can be found everywhere in consumer electronics, A USB connection doesn’t have to be external. If your MCU or CPU of choice has USB capability, you can also consider using USB for embedded connection with other MCUs or CPUs in your system. USB has built-in data encoding to reduce electromagnetic interference and link power management for high efficiency. USB also adds flexibility to client software that has many low-level drivers.
6. What if you need more flexibility than a standard USB connection can provide?
The advent of the USB Type-C® protocol has greatly improved USB flexibility. USB Type-c can create peripherals that act as USB hosts or USB devices, enabling the system to respond to different types of connections in a variety of ways. USB Type-C active multiplexer also ensures that the interface is configured correctly while providing signal integrity that conforms to USB specifications.
Active multiplexers such as TUSB542 and TUSB1042I should be used in your standard Type-C design. USB Type-C also facilitates the transfer of multiple types of high-speed data on the same interface, such as DisplayPort, HD multimedia interface, UART, and other video or custom interfaces. TUSB1146 and TUSB1064 are critical for the system to enable its alternate mode feature.
Others: For technical details on the USB protocol and USB implementation, check out the resources below.