Interface - I/O expanders are devices that allow for the expansion of input/output (I/O) capabilities of a microcontroller or microprocessor. These devices are commonly used in embedded systems, where the number of I/O pins available on the microcontroller or microprocessor is limited. In this article, we will discuss the mainstream models of interface - I/O expanders.

1. Serial Peripheral Interface (SPI) I/O Expanders

SPI I/O expanders are one of the most commonly used interface - I/O expanders. These devices use the SPI protocol to communicate with the microcontroller or microprocessor. SPI I/O expanders are available in various configurations, ranging from 8-bit to 16-bit I/O ports. These devices are easy to use and require minimal hardware resources. They are also relatively inexpensive, making them a popular choice for many embedded systems.

2. Inter-Integrated Circuit (I2C) I/O Expanders

I2C I/O expanders are another popular choice for interface - I/O expanders. These devices use the I2C protocol to communicate with the microcontroller or microprocessor. I2C I/O expanders are available in various configurations, ranging from 8-bit to 16-bit I/O ports. These devices are easy to use and require minimal hardware resources. They are also relatively inexpensive, making them a popular choice for many embedded systems.

3. Universal Asynchronous Receiver/Transmitter (UART) I/O Expanders

UART I/O expanders are less commonly used than SPI and I2C I/O expanders. These devices use the UART protocol to communicate with the microcontroller or microprocessor. UART I/O expanders are available in various configurations, ranging from 8-bit to 16-bit I/O ports. These devices are more complex to use than SPI and I2C I/O expanders and require more hardware resources. They are also more expensive than SPI and I2C I/O expanders.

4. Parallel I/O Expanders

Parallel I/O expanders are the oldest and most basic type of interface - I/O expanders. These devices use parallel communication to communicate with the microcontroller or microprocessor. Parallel I/O expanders are available in various configurations, ranging from 8-bit to 16-bit I/O ports. These devices are more complex to use than SPI and I2C I/O expanders and require more hardware resources. They are also more expensive than SPI and I2C I/O expanders.

5. USB I/O Expanders

USB I/O expanders are a relatively new type of interface - I/O expanders. These devices use the USB protocol to communicate with the microcontroller or microprocessor. USB I/O expanders are available in various configurations, ranging from 8-bit to 16-bit I/O ports. These devices are easy to use and require minimal hardware resources. They are also relatively inexpensive, making them a popular choice for many embedded systems.

In conclusion, interface - I/O expanders are essential devices for expanding the I/O capabilities of microcontrollers and microprocessors. The mainstream models of interface - I/O expanders include SPI, I2C, UART, parallel, and USB I/O expanders. Each of these models has its advantages and disadvantages, and the choice of which model to use depends on the specific requirements of the embedded system.