Such troubles occur when designing circuits...

Recent one-chip microcontrollers have various communication methods and many analog peripherals built-in, making it possible to eliminate the circuit design that would normally be required externally. Additionally, there is a strong tendency for microcontrollers to be standardized and shared among hiring companies, and I believe that the reality is that they do not want to replace microcontrollers.

However, have you ever had the problem of "a few terminals are missing" when the design scale exceeds your expectations?

Therefore, I/O expanders are available as a means of expanding the number of I/Os in circuit designs that are difficult to replace.

*I/O expander is a common way to compensate for the lack of I/O ports on a microcontroller with an external device, and is similar to a USB hub used when there are not enough USB ports.

I/O expander implementation using general-purpose microcontroller "EFM8"

At Silicon Labs, it is possible to implement I/O expanders using the general-purpose microcontroller "EFM8".

*EFM8 is an 8-bit microcontroller (MCU) provided by Silicon Labs.

By using a general-purpose microcontrollerI/OIs it necessary to implement an expander? You might think that.

When it comes to searching for commercially available products, there are actually many options, includingoptions for expansion scale, flexibility in I / O settings, and whether they will be available in the future. There are many points that need to be considered, making it difficult to make a selection.

Therefore, I would like to introduce the featuresof I/O expander implementation using "EFM8", which enables a higher degree of design freedom.

Feature 1: The number of I/Os can be expanded from 8 to 24!

I/O expander implementation using "EFM8"enables expansion of8to24 lines externally. Being able to easily expand the number of I/Os without replacing the microcontroller means that changes in circuit design can be kept to a minimum.

Control ofthis I/O expander can be configured using commands viaI2C. As a mechanism,

By using two signal lines, the main microcontroller's clock (SCL) and data input/output (SDA), you can expand the number of input/output signal lines.

In addition,as shown in the diagram on the right,by coexisting two EFM8s on the same I2C bus,itispossibletoexpandI/O to a maximum of 24lines x2sets (maximum48lines).

Feature 3: Freedom of setting for each terminal!

Since"EFM8" is a general-purpose microcontroller,a wider range of settings can be made than with a singleI/O expander.

There is a high degree of freedom in setting each terminal, and settings as shown in the figure on the right are possible.For example, by assigning LED port outputs and switch inputs to all bits of EFM8, the number of I/Os on the main microcontroller can be reduced.

In this way, achieving appropriate functional distribution contributes to simplifying the main microcontroller's circuit design and processing.

*When using the input terminal interrupt detection function, it is necessary to add an IRQ terminal.

Feature 4: Small mounting area!

For those considering adopting an I/O expander, the mounting area may be a concern.

"EFM8" has a wide lineup and is aone-chip microcontroller with a size of2.0 mm to 5.0 mm square, depending on the I/O expansion scale.

Therefore,I/Oresources can be supplemented with a small mounting area.

EFM8 also operates on a single power supply and does not require an oscillator, so it does not require additional mounting space.

These features enable a high degree of freedom in designing I/O expanders using EFM8.

If you are having trouble selecting an I/O expander, please consider this.

Evaluation boards are also available for evaluation and development.

https://www.silabs.com/development-tools/mcu/8-bit/bb52-pk5206b-efm8bb5-pro-kit?tab=overview

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