arm7 键盘扫描程序
时间: 2023-11-27 10:55:06 浏览: 28
键盘扫描是在嵌入式系统中常见的任务之一。以下是一个基于 ARM7 的键盘扫描程序示例:
```c
#include <LPC214x.h>
#define ROWS 4
#define COLS 4
unsigned char keymap[ROWS][COLS] = {
{'1', '2', '3', 'A'},
{'4', '5', '6', 'B'},
{'7', '8', '9', 'C'},
{'*', '0', '#', 'D'}
};
void delay_ms(unsigned int count) {
unsigned int i, j;
for (i = 0; i < count; i++)
for (j = 0; j < 5000; j++);
}
unsigned char scan_key(void) {
unsigned char row, col;
IO0DIR |= 0x0000F000; // Configure P0.12 to P0.15 as output
IO0SET |= 0x0000F000; // Set P0.12 to P0.15 high
IO0DIR &= ~0x00000FF0; // Configure P0.4 to P0.11 as input
for (col = 0; col < COLS; col++) {
IO0CLR = 0x0000F000; // Set P0.12 to P0.15 low
IO0SET = (1 << (12 + col)); // Set one column high
for (row = 0; row < ROWS; row++) {
if (!(IO0PIN & (1 << (4 + row)))) { // Check if key is pressed
delay_ms(50); // Debounce delay
if (!(IO0PIN & (1 << (4 + row)))) // Check if key is still pressed
return keymap[row][col]; // Return key value
}
}
}
return 0; // No key pressed
}
int main(void) {
unsigned char key;
IO0DIR |= (1 << 31); // Configure P0.31 as output for LED
while (1) {
key = scan_key();
if (key) {
IO0SET = (1 << 31); // Turn on LED
while (scan_key()); // Wait for key release
IO0CLR = (1 << 31); // Turn off LED
}
}
return 0;
}
```
该程序使用 IO0.4 到 IO0.7 作为键盘的行,IO0.12 到 IO0.15 作为键盘的列。在扫描过程中,首先将 IO0.12 到 IO0.15 配置为输出,并将其高电平设置为 1,然后将 IO0.4 到 IO0.7 配置为输入。然后,程序依次将每个列设置为低电平,并检查每个行是否被按下。如果某个键被按下,则返回该键的值。在返回键值之前,程序还会进行去抖动处理,以避免错误的键值返回。
主函数中,程序不断调用 scan_key() 函数来扫描键盘。如果有键被按下,LED 将被打开,直到键被释放为止。