Enhance your microcontroller with 8 additional pins using the MCP23008 port expander. This device uses just two I2C pins, which can be shared with other I2C devices, and in return offers 8 general-purpose pins. You can configure each of these 8 pins as input, output, or input with a pullup. Plus, it can send an interrupt via an external pin when any input changes, so you don't have to constantly poll the chip. Operate this chip from 2.7 - 5.5V, suitable for both 3.3V and 5V setups. Each I/O pin can sink/source up to 20mA, making it great for powering LEDs. Pair it with a high-power MOSFET if you need more current. Its DIP package allows it to easily plug into any breadboard or perfboard. You can set the I2C address by connecting the ADDR0 - 2 pins to power or ground, enabling up to 8 unique addresses. That means 8 chips can share a single I2C bus, giving you a total of 64 I/O pins! We've used this chip in our SPI/I2C backpack and found it highly reliable and easy to start using. We even have an Arduino library with example code for setting pin states, reading and writing individual pins, and setting pullups.
Using the MCP23008 port expander is easy. First, connect it to your microcontroller using the two I2C pins. You can share these pins with other I2C devices. Then, you can set each of the 8 pins according to your needs - as an input, output, or input with a pullup. If you want to know when an input changes, just connect an external pin to receive an interrupt. This way, you don't have to keep checking the chip. The chip works well with both 3.3V and 5V setups, as it can operate from 2.7 - 5.5V. Each I/O pin can handle up to 20mA, so it's good for powering LEDs. If you need more power, team it up with a high - power MOSFET. The DIP package allows you to simply plug it into a breadboard or perfboard. To set different I2C addresses, connect the ADDR0 - 2 pins to power or ground. You can have up to 8 chips sharing a single I2C bus. We've included an Arduino library with example code to help you get started. Just follow the code to set pin states, read and write from individual pins, and set pullups. As for maintenance, keep it in a dry and clean environment. Avoid exposing it to extreme temperatures or humidity. If you're not using it for a long time, store it properly in an anti - static bag.
