Keyboard circuit capable of improving key-press scanning speed

Abstract

The invention discloses a keyboard circuit capable of improving key-press scanning speed. In the keyboard circuit, one ends of each column line and row line are connected with a power supply through a current limiting resistor; the other ends of the column line which are multiplexed by a PNP (positive-negative-positive) switching transistor and the other ends of the m column lines which are multiplexed by an NPN (negative-positive-negative) switching transistor are connected correspondingly with the I / O interfaces, namely P1.1, P1.2,...,P1.m after being multiplexed; meanwhile, the half of therest column lines which are multiplexed by the PNP switching transistor and the other half which are multiplexed by the NPN switching transistor are correspondingly connected with I / O interfaces, namely P[1.(m+1)], P[1.(m+2)],...,P[1.(m +n) / 2]; the base of each switching transistor is connected to the I / O interface P[1.0] through the current limiting resistor; the column line and the row line of each key-press are connected with the ground wire through a combination switch; all the column lines are connected to the inputs of interrupt Input port through an AND circuit unit. The keyboard circuit provided by the invention has the advantages that when the sum of the column lines and the row lines of the key circuit is 2N, the required number of the I / O interfaces is N+1, and when the sum of the column lines and the row lines is 2N+1, the required number of the I / O interfaces is N+2 and the values of column and the row can be obtained after scanning for two times.

Description

technical field [0001] The invention relates to the field of input equipment for computers and automatic control systems, in particular to a keyboard circuit for improving the scanning speed of the keyboard. Background technique [0002] At present, the general-purpose keyboards are mainly matrix keyboards. In keyboard applications, how to increase the keyboard scanning speed and how to increase the number of keys as much as possible under a certain number of I / O ports are two important issues. Traditionally, the line inversion method can be used to scan the keyboard through fewer scanning steps, thereby reducing the keyboard scanning time. For example, to realize an N×N matrix keyboard, the line inversion method can be used to implement a simple scanning program, but the required The number of I / O ports is 2N, which occupies a large number of I / O ports. A keyboard circuit is disclosed in the patent document with application number 200420014528, which can effectively reduce...

AI Technical Summary

Problems solved by technology

A keyboard circuit is disclosed in the patent document with application number 200420014528, which can effectively reduce the number of occupied I / O ports, and the number of I / O ports required to realize N×N matrix keyboard scanning is N+1. However, the scanning process is complicated, and it needs to scan N times to determine a key value, and the purpose of reducing the number of occupied I / O ports cannot be achieved when the number of rows and columns of the matrix keyboard is not equal.

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