Q: What is the basic principle of DIP switch and MCU interface?

Connecting a microcontroller to a microcontroller using a dual-in-line package (DIP) switch is a common application. These switches, commonly known as "DIPs," are used in a variety of designs, from traditional DIPs suitable for breadboard prototyping to surface-mount " piano " types to rotary switches for easy hexadecimal reading .

In this article, we will take a closer look at rotary switches and explore how to integrate them into our microcontroller designs. The techniques presented in this article are generally applicable to all microcontroller designs.

Start with the rules

Let's start with a simple rule: no floating inputs allowed . A floating input occurs when a microcontroller pin is configured as an input but is otherwise unconnected. An example is shown here. When the switch is closed, the associated pin is tied to the positive rail. When the switch is open, the pin is floating.

Optimization solutions

• The internal pull-up resistor is enabled using the microcontroller's special function registers
• The common element of the switch is connected to ground

Looking back at the microcontroller schematic and its associated pull-up resistors, we see an inversion. For example, when the switch is in the 1 position, there are three positive logic inputs at positions 2, 4, and 8. Meanwhile, if the complementary switch is installed, there is a positive logic (active-high) input corresponding to a 1 signal.
From a programming perspective, this difference in the physical switch code is insignificant. A simple bit-invert instruction will make them equal. From a troubleshooting or educational perspective, the complementary version may be easier to understand because it results in a positive logic value at the microcontroller pin.

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