实践中,单片机端口在衔接开关器材时都要考虑消抖的问题,或在硬件上添加推迟,或是添加软件推迟查询的功能模块。这儿,咱们考虑这样一个检测电路:单片机衔接一个开关和两个LED。程序是这样的,假如开关的消抖正确,就点亮LED1,不然就闪亮LED2。按下开关,点亮LED1,开释开关,LED1即平息。咱们参加20毫秒的消抖推迟时间。当检测到开关为低电平时,单片机在推迟20毫秒后再次检测开关的状况。假如此刻开关状况为高,则LED2就闪亮,如为低则点亮LED1。
源代码:
led1
led2
switch1
ORG 0000h
setb switch1
setb led1
setb led2
wait:
jb switch1,wait
call debounce_delay
jb switch1,c1_wait
//switch low even after debouncing period
//switch has been succesfully debounced
clr led1
jnb switch1,$
setb led1
ajmp wait
c1_wait:
//Switch PIN high after debounce period so error in debouncing
cpl led2
ajmp wait
debounce_delay:
mov r7,#245
l1_debounce_delay:
mov r6,#40
djnz r6,$
djnz r7,l1_debounce_delay
ret
END