“This article describes a simple routine to allow you to use a low-cost eight-digit LED module to display formatted data from a microcontroller project
The routine will work with almost any microcontroller; as a demonstration of the routine I’ve written a simple stopwatch program for the ATtiny85 or ATtiny402.
Seven-segment LED displays are a great way to provide clear, readable output from a project such as a digital clock, voltmeter, or frequency meter. They are also useful for providing debugging information when developing a project. The only downside is that there are a lot of pins to wire up, but you can avoid this by using a serial seven-segment display module that you connect to with a simple I2C or SPI interface.”