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Experiment: 4x4 Keypad Module: Touch-Sensitive 4*4 Membrane Matrix Keyboard for External Expansion and Control of 16-Bit Microcontrollers Matrix Keyboard A matrix keyboard is an external device used with microcontrollers, featuring a grid layout that simplifies key identification. In this setup, columns are linked to the power supply and microcontroller outputs, while rows are inputs. This reduces the number of I/O ports needed. Large keyboards use a matrix arrangement to minimize I/O usage, with each key at the intersection of rows and columns. A single port can manage multiple keys in a matrix, increasing efficiency. For instance, a 4x4 matrix can handle 16 keys, which is more than direct connections. Adding more lines to the matrix increases the number of keys that can be handled exponentially, making it an efficient method for managing many keys. Membrane Keyboard

A membrane keyboard, also known as a membrane switch, is a popular choice for its blend of aesthetics and functionality. It consists of four key components: the panel, upper circuit, isolation layer, and lower circuit. This type of keyboard is valued for its modern design, compactness, light weight, and good sealing properties. It is also resistant to moisture, dust, oil, acids, alkalis, and shock, making it durable. Due to these features, it is widely used in various industries such as medical, computer, digital machinery, electronic scales, telecommunications, appliances, and gaming. Advantages:

Sleek and novel appearance. Compact size, thin thickness, lightweight, which is conducive to the trend of lightweight, thin, short, small, and highly intelligent notebook keyboard development. Moisture-proof, dust-proof, oil-resistant, and resistant to harmful gases, with strong sealing properties, acid and alkali resistance, and shock resistance. Long service life and resistance to bending and folding Key recognition method

In this way, when no key is pressed, all input lines are at a high logic level, indicating that no key is pressed. The output lines are at a low logic level. Once a key is pressed, the corresponding input line will be pulled down. By reading the status of the input lines, it can be determined whether a key is pressed.

I. Row scanning method, also known as row (or column) scanning query method, is one of the most commonly used key recognition methods.

Determine if any keys are pressed: Set all row lines Y0-Y3 to a low logic level, then detect the status of the column lines. If any column line is at a low logic level, it indicates that a key on the keyboard has been pressed, and the closed key is located among the 4 keys where the low logic line intersects with the 4 row lines. If all column lines are at a high logic level, then no keys are pressed on the keyboard.

Identifying the position of the pressed key involves determining which specific key is closed. The process is as follows: Set each row line to a low logic level one at a time, while keeping the other lines at a high logic level. Once you find a row line at a low logic level, examine the logic levels of each column line in sequence. If a column line is also at a low logic level, the key at the intersection of that column and the row set to low is the closed key.

II. High-low logic level flip method

When a key is pressed, the high bits switch from 1 to 0, showing the row, and one of the low bits changes from 1 to 0, indicating the column. An OR operation combines these to determine the key's position. Keyboard and display processing can be intricate, primarily due to user habits and external factors, not the microcontroller. Organizing and logically representing the keyboard processing through algorithms before coding is crucial for creating efficient and effective programs. Flexible Membrane Keyboard A flexible membrane keyboard consists of soft film layers, including PET for its electrical properties and low-resistance conductive coatings for circuit patterns. This design allows the keyboard to adapt to flat and curved surfaces, with integrated lead-out wires providing bendable connections to the device's circuitry. Flat Three-Dimensional Membrane Keyboard This membrane keyboard has keys slightly raised, known as 3D key switches, which improve key recognition and tactile sensitivity, and add decorative appeal. Designing these keys involves precise positioning during mold pressing, and the height of the raised portion should not exceed twice the thickness of the substrate. Various designs can be applied to the protrusions for aesthetic purposes.

Module Parameters Contact resistance: 500 ohms Insulation resistance: 100 Megaohms Critical operating force: 150-200 Newtons Bounce time: 1 millisecond Lifespan: 100 million cycles Operating temperature: 60 degrees Celsius

1.Electrical Characteristics: Rated Current: 35V (DC), 100mA, 1W Contact Resistance: 10Ω~500Ω (varies with different wire lengths depending on materials used for wires) Insulation Resistance: 100MΩ 100V Dielectric Strength: 250VRms (50~60Hz 1min) Electric Shock Vibration: <5ms Lifetime: Touch Type: ≥1 million times 2.Mechanical Performance: Operating Pressure: Touch: 170~397g (6~14oz) Switch Travel: Touch type: 0.6~1.5mm

3.Environmental Parameters: Operating Temperature: -40 to +80 Storage Temperature: -40 to +80 Temperature: From 40, 90% to 95%, 240 hours Vibration: 20G, maximum (10~200Hz, Mil-SLD-202 M204, Condition B) TAG:Keypad Module;electronic components; electronic product design

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