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Interrupt-driven keypad scanning method and apparatus

A keyboard scanning, pocket-sized technology, applied in dynamic coding, data processing input/output process, instruments, etc., can solve the problems of increasing software complexity, high cost, large product size, etc., to reduce scanning complexity and cost. , the effect of reducing the number of

Inactive Publication Date: 2003-12-10
MOTOROLA INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Traditional keypad scanning techniques typically require circuitry in addition to the microcontroller, resulting in larger product size, higher cost, and increased software complexity

Method used

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  • Interrupt-driven keypad scanning method and apparatus
  • Interrupt-driven keypad scanning method and apparatus
  • Interrupt-driven keypad scanning method and apparatus

Examples

Experimental program
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Embodiment Construction

[0020] figure 1 A schematic diagram of a keypad according to a preferred embodiment is shown. The keypad matrix 70 of the electronic device 100 has: for example, 6 rows of 4 keys: 11-14, 21-24, 31-34, 41-44, 51-54, 61-64. In this example, the electronic device 100 is a cell phone handset, however, other electronic devices with keypads, such as remote controls, cordless phones, and electronic calculators may use the interrupt-driven keypad scanning method and apparatus. A microcontroller 99 , such as a Motorola HC12 microcontroller, is connected to the row and column lines of the keypad matrix 70 .

[0021] With the microcontroller 99 the row lines 15, 25, 35, 45, 55, 65 of the keypad matrix 70 can be set to one of two states: output state latch logic 0 (low signal level); High-impedance input state when pull-up resistors 18, 28, 38, 48, 58, 68 are enabled. Preferably, the pull-up resistors are software enabled and controlled by microcontroller 99 . Of course, other row lin...

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PUM

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Abstract

The interrupt-driven keypad scanning method and apparatus accurately interprets keypresses in single-keypress applications. Initially, interrupts associated with each column line of a keypad matrix are set to trigger when a key is pressed. Once an interrupt triggers, a microcontroller polls the row lines to determine which key, if any, was validly pressed. If exactly one keypress is detected, the keypress is valid. Next, the interrupt for the valid key's column line is enabled while the other column line interrupts are disabled. When a next interrupt is received, the keypad returns to the row-scan state for determination of which keys are depressed. If no keys are depressed, which occurs when the validly-pressed key has been released, the keypad returns to the keypress-detect state.

Description

Technical field: [0001] The invention relates to a miniature keyboard interface of an electronic device, in particular to a scanning method and device of the miniature keyboard. Background technique: [0002] A keypad scanning technique utilizes a dedicated microprocessor to periodically timed access (typically every 20-30 ms) the state of the keypad matrix to determine when a key is pressed or released. However, since the keypad matrix only contains useful information for a portion of the time it is timed to be accessed, periodic timed accesses result in excessive keypad read impulse noise. However, less frequent timed access will result in missed key presses and key releases, which is undesirable. [0003] Another keypad scanning technique uses an interrupt to the microcontroller to indicate when the keypad changes state. However, not every keypad state change provides useful information to the microcontroller. For example, in some applications, only one key press can b...

Claims

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Application Information

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IPC IPC(8): H03M11/20
CPCH03M11/20
Inventor 丹尼尔·F·金莫曼
Owner MOTOROLA INC
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