¶ GPIO 编程
本章以youyeetooRJ的GPIO3_PD4为例讲解GPIO的使用
¶ 1 原理图位置
¶ 2 接口的使用
将GPIO 124设置为用户态操作
echo 124 > /sys/class/gpio/export
将GPIO 124设置为输出
echo out > /sys/class/gpio/gpio124/direction
在GPIO 124为输出的情形下，设置电平
高电平
echo 1 > /sys/class/gpio/gpio124/value
低电平
echo 0 > /sys/class/gpio/gpio124/value
将GPIO 124设置为输入
echo in > /sys/class/gpio/gpio124/direction
在GPIO 124为输入的情形下，读取其电平，1为高，0为低
cat sys/class/gpio/gpio124/value
取消GPIO 124用户态操作
echo 124 > /sys/class/gpio/unexport
¶ 3 GPIO输出PWM方波 DEMO
- 读者可以通过调整参数时间自行控制方波周期
cat GPOI_PWM.sh
#!/bin/bash
echo 124 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio124/direction
echo 1 > /sys/class/gpio/gpio124/value
while true; do
echo 1 > /sys/class/gpio/gpio124/value
sleep $1 && echo "delay $1"
echo 0 > /sys/class/gpio/gpio124/value
sleep $1 && echo "delay $1"
done
root@linaro-alip:/# ./GPIO_PWM.sh 0.01
delay 0.01
delay 0.01
delay 0.01
...
- 现象如图
¶ 4 创建测试GPIO的APP
首先按照创建APP章节创建好APP，这里贴出关键代码供客户验证，编译好的APP会提供。
资料下载，点击跳转
¶ 4.1 效果演示
¶ 4.2 关键代码如下
- gpio\app\src\main\java\com\youyeetoo\rj_gpio\MainActivity.kt
package com.youyeetoo.rj_gpio
import android.os.Bundle
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.activity.enableEdgeToEdge
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.Spacer
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.height
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.text.KeyboardOptions
import androidx.compose.foundation.verticalScroll
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.Delete
import androidx.compose.material3.Button
import androidx.compose.material3.Checkbox
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.OutlinedTextField
import androidx.compose.material3.Scaffold
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.LaunchedEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateListOf
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.text.input.KeyboardType
import androidx.compose.ui.unit.dp
import com.youyeetoo.rj_gpio.ui.theme.Rj_gpioTheme
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
enableEdgeToEdge()
setContent {
Rj_gpioTheme {
Scaffold(modifier = Modifier.fillMaxSize()) { innerPadding ->
GpioList(modifier = Modifier.padding(innerPadding))
}
}
}
}
}
@Composable
fun GpioList(modifier: Modifier = Modifier) {
val items = remember { mutableStateListOf(124) } // 默认示例 GPIO3_D4
var bankInput by remember { mutableStateOf("3") }
var pinInput by remember { mutableStateOf("D4") } // 如 A0/B3/D4
var inputError by remember { mutableStateOf<String?>(null) }
val scroll = rememberScrollState()
Column(
modifier = modifier
.fillMaxSize()
.padding(16.dp)
.verticalScroll(scroll),
verticalArrangement = Arrangement.spacedBy(16.dp)
) {
Row(verticalAlignment = Alignment.CenterVertically) {
OutlinedTextField(
value = bankInput,
onValueChange = { bankInput = it.filter { ch -> ch.isDigit() } },
label = { Text("Bank (例: 3)") },
singleLine = true,
keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Number),
modifier = Modifier.weight(1f)
)
Spacer(Modifier.width(8.dp))
OutlinedTextField(
value = pinInput,
onValueChange = { pinInput = it.filter { ch -> ch.isLetterOrDigit() } },
label = { Text("引脚 (例: D4)") },
singleLine = true,
modifier = Modifier.weight(1f)
)
Spacer(Modifier.width(8.dp))
Button(onClick = {
val result = parseGpio(bankInput, pinInput)
if (result == null) {
inputError = "格式错误，例如 Bank=3, 引脚=D4"
} else {
val gpioNum = result
if (gpioNum !in items) {
items.add(gpioNum)
}
inputError = null
}
}) { Text("添加") }
}
inputError?.let { Text(it) }
items.forEach { gpioNum ->
GpioCard(
gpioNum = gpioNum,
onRemove = { items.remove(gpioNum) }
)
}
}
}
@Composable
fun GpioCard(gpioNum: Int, onRemove: () -> Unit) {
var isOn by remember(gpioNum) { mutableStateOf(false) }
var status by remember(gpioNum) { mutableStateOf("未初始化") }
var isInput by remember(gpioNum) { mutableStateOf(false) }
LaunchedEffect(gpioNum, isInput) {
runCatching {
GpioSysfs.setDirection(gpioNum, !isInput)
isOn = GpioSysfs.read(gpioNum)
status = if (isInput) "已设置为输入" else "已设置为输出"
}.onFailure { status = "初始化失败: ${it.message}" }
}
Column(
modifier = Modifier
.fillMaxWidth()
.padding(12.dp)
) {
Row(verticalAlignment = Alignment.CenterVertically) {
Text("GPIO$gpioNum", modifier = Modifier.weight(1f))
IconButton(onClick = onRemove) {
Icon(Icons.Default.Delete, contentDescription = "删除")
}
}
Row(verticalAlignment = Alignment.CenterVertically) {
Checkbox(checked = isInput, onCheckedChange = { isInput = it })
Text("输入模式（只读）")
}
Text(status)
Spacer(Modifier.height(8.dp))
Row(horizontalArrangement = Arrangement.spacedBy(12.dp)) {
Button(onClick = {
runCatching { GpioSysfs.setDirection(gpioNum, !isInput) }
.onFailure { status = "设方向失败: ${it.message}" }
}) {
Text(if (isInput) "设为输入" else "设为输出")
}
Button(onClick = {
runCatching {
isOn = GpioSysfs.read(gpioNum)
status = if (isOn) "当前值: 1(高电平)" else "当前值: 0(低电平)"
}.onFailure { status = "读取失败: ${it.message}" }
}) {
Text("读取")
}
}
Spacer(Modifier.height(8.dp))
Button(
onClick = {
val next = !isOn
runCatching { GpioSysfs.write(gpioNum, next) }
.onSuccess {
isOn = next
status = if (next) "已写 1" else "已写 0"
}
.onFailure { status = "写失败: ${it.message}" }
},
enabled = !isInput
) {
Text(if (isOn) "写 0（关闭）" else "写 1（开启）")
}
}
}
private fun parseGpio(bankStr: String, pinStr: String): Int? {
val bank = bankStr.toIntOrNull() ?: return null
if (pinStr.length !in 2..3) return null
val letter = pinStr.first().uppercaseChar()
val port = when (letter) {
'A' -> 0
'B' -> 1
'C' -> 2
'D' -> 3
'E' -> 4
'F' -> 5
'G' -> 6
'H' -> 7
else -> return null
}
val offsetPart = pinStr.drop(1)
val offset = offsetPart.toIntOrNull() ?: return null
if (offset !in 0..7) return null
return bank * 32 + port * 8 + offset
}
- gpio\app\src\main\java\com\youyeetoo\rj_gpio\GpioSysfs.kt
package com.youyeetoo.rj_gpio
import java.io.File
import java.io.IOException
/**
* 简单 sysfs GPIO 读写工具：支持指定 GPIO 号。
* 需具备写 /sys/class/gpio 权限（system/priv-app 或 root）。
*/
object GpioSysfs {
private val exportFile = File("/sys/class/gpio/export")
private val unexportFile = File("/sys/class/gpio/unexport")
@Throws(IOException::class)
fun ensureExported(gpioNum: Int) {
val dir = File("/sys/class/gpio/gpio$gpioNum")
if (!dir.exists()) exportFile.writeText(gpioNum.toString())
}
@Throws(IOException::class)
fun setDirection(gpioNum: Int, out: Boolean) {
ensureExported(gpioNum)
File("/sys/class/gpio/gpio$gpioNum/direction").writeText(if (out) "out" else "in")
}
@Throws(IOException::class)
fun write(gpioNum: Int, value: Boolean) {
ensureExported(gpioNum)
File("/sys/class/gpio/gpio$gpioNum/value").writeText(if (value) "1" else "0")
}
@Throws(IOException::class)
fun read(gpioNum: Int): Boolean {
ensureExported(gpioNum)
return File("/sys/class/gpio/gpio$gpioNum/value").readText().trim() == "1"
}
fun cleanup(gpioNum: Int) {
val dir = File("/sys/class/gpio/gpio$gpioNum")
if (dir.exists()) runCatching { unexportFile.writeText(gpioNum.toString()) }
}
}