在Raspberry Pi 4(Ubuntu 20.04.1)中运行自定义bash脚本以控制GPIO的高CPU使用率

Question

我写了一个bash脚本来打开/关闭GPIO以控制风扇，但这会导致CPU使用率高，我不知道为什么。

它可以工作，但每当它将状态从关闭更改为打开或反之亦然时，脚本就会冻结，导致CPU使用率高，大约5分钟后，它会更改状态，CPU使用率恢复正常。大约20-60秒后，问题再次出现。

有人能帮我理解我的剧本出了什么问题吗？

[运行Ubuntu 20.04]的Raspberry Pi 4]

#!/bin/bash
export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin"
gpio -g mode 3 out
on=48000
off=44000
while true; do
cpu=$(</sys/class/thermal/thermal_zone0/temp)    # get CPU temperature
if (( "$cpu" > "$on" )); then
gpio -g write 3 1    # turn fan ON
echo "CPU Hot"
sleep 60
fi
if (( "$off" > "$cpu" )); then
echo "CPU Cool."
gpio -g write 3 0    # turn fan OFF
sleep 5
fi
done

Answer 1

好的，所以我能够解决这个问题，多亏了@shellter。。。

问题是当CPU温度在4800和4400之间时，脚本没有任何condition要处理

解决方案的基本思想是：

if (CPU is Hot); then
turn fan ON
set boolean = true
sleep 60 sec
else if (CPU is Cool); then
turn fan OFF
set boolean = false
sleep 5 sec
else (when CPU is neither Hot OR Cool.. somewhere between 4400 && 4800)
if (boolean is true.. meaning CPU didn't go below 4400); then
sleep 60 sec
else (boolean is false.. meaning CPU didn't go above 4800); then
sleep 5 sec 

---

工作代码为：

#!/bin/bash
export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin"
gpio -g mode 3 out
on=48000
off=44000
hot=false
while true; do
cpu=$(</sys/class/thermal/thermal_zone0/temp)
if (( "$cpu" > "$on" )); then
echo "CPU Hot"
hot=true
gpio -g write 3 1    # turn fan ON
sleep 60
elif (( "$off" > "$cpu" )); then
echo "CPU Cool."
hot=false
gpio -g write 3 0    # turn fan OFF
sleep 5
else
if [ "$hot" = true ]; then
echo "CPU still Hot"
sleep 60
else
echo "CPU Cool"
sleep 5
fi
fi
done