UART (Universal Asynchronous Receiver/Transmitter) and USB (Universal Serial Bus) are both common serial communication interfaces used for transmitting data between devices, but they differ significantly in their functionality, complexity, and typical applications.
UART (Universal Asynchronous Receiver/Transmitter)
UART is one of the oldest and simplest serial communication protocols. It's primarily used for point-to-point communication between two devices.
- Asynchronous Communication: UART does not require a clock signal to be transmitted alongside the data. Instead, it relies on start and stop bits to synchronize the communication.
- Simplicity: It is relatively easy to implement in hardware and software.
- Low Speed: Typically used for lower data rates compared to USB.
- Applications: Commonly found in embedded systems, GPS modules, Bluetooth modules, and serial terminals.
- Data Transmission: Transmits data serially, one bit at a time, over a single wire (plus ground).
- No Addressing: UART does not support addressing multiple devices on a single bus. It is point-to-point.
- Framing: Data is transmitted in frames, which include:
- Start bit
- Data bits (typically 8)
- Parity bit (optional)
- Stop bit
USB (Universal Serial Bus)
USB is a much more complex and versatile serial communication standard designed for connecting peripherals to a computer.
- High Speed: Offers significantly higher data transfer rates than UART.
- Versatility: Supports a wide range of devices, including storage devices, keyboards, mice, printers, and cameras.
- Hot-Pluggable: Devices can be connected and disconnected while the system is running.
- Power Delivery: Can provide power to connected devices.
- Addressing: USB supports addressing multiple devices connected to a single bus via a tiered, tree-like structure, with a host controller at the root.
- Protocol: Uses a more complex protocol with sophisticated error checking and flow control.
- Device Classes: Defines standard device classes (e.g., mass storage, human interface device) to simplify driver development.
- Multiple Transfer Types: Supports different transfer types like control, bulk, interrupt, and isochronous transfers to cater to various device requirements.
Key Differences in a Table:
| Feature | UART | USB |
|---|---|---|
| Speed | Low | High |
| Complexity | Simple | Complex |
| Addressing | Point-to-Point (No Addressing) | Multiple Devices (Addressing Supported) |
| Hot-Pluggable | No | Yes |
| Power Delivery | No | Yes |
| Applications | Embedded systems, simple peripherals | Wide range of peripherals, storage |
| Synchronization | Asynchronous | Synchronous |
In summary, UART is a simple, low-speed serial communication protocol suitable for point-to-point communication in embedded systems, while USB is a complex, high-speed serial communication standard designed for connecting a wide range of peripherals to a computer, offering features like hot-plugging and power delivery.
