GPIO使用说明

这篇文章主要介绍如何在Android系统下控制GPIO。

获取GPIO数值

想要控制GPIO，必须知道其对应的GPIO数值。

计算方法

GPIO数值计算方法为：Number = Range Base + Pin Index。

  1. Range Base表示Range基数。
  2. Pin Index表示GPIO管脚相对于Range的偏移。

GPIO数值计算举例

  1. 获取Range Base：
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# cat /sys/kernel/debug/pinctrl/fe000000.apb4\:pinctrl\@4000-pinctrl-meson/gpio-ranges
GPIO ranges handled:
0: periphs-banks GPIOS [355 - 511] PINS [0 - 156]
  1. 获取Pin Index：
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# cat /sys/kernel/debug/pinctrl/fe000000.apb4\:pinctrl\@4000-pinctrl-meson/pins
registered pins: 157
pin 0 (GPIOB_0)  fe000000.apb4:pinctrl@4000
pin 1 (GPIOB_1)  fe000000.apb4:pinctrl@4000
pin 2 (GPIOB_2)  fe000000.apb4:pinctrl@4000
pin 3 (GPIOB_3)  fe000000.apb4:pinctrl@4000
pin 4 (GPIOB_4)  fe000000.apb4:pinctrl@4000
pin 5 (GPIOB_5)  fe000000.apb4:pinctrl@4000
pin 6 (GPIOB_6)  fe000000.apb4:pinctrl@4000
pin 7 (GPIOB_7)  fe000000.apb4:pinctrl@4000
pin 8 (GPIOB_8)  fe000000.apb4:pinctrl@4000
pin 9 (GPIOB_9)  fe000000.apb4:pinctrl@4000
...
pin 109 (GPIOT_18)  fe000000.apb4:pinctrl@4000
pin 110 (GPIOT_19)  fe000000.apb4:pinctrl@4000
...
  1. 获取GPIO数值：

以GPIOT_19为例

GPIOT_19 = Range Base + Pin Index = 355 + 110 = 465

GPIO用法

在获取到GPIO数值后就可以通过如下的步骤来控制GPIO，以GPIOT_19（Number 465）为例：

ADB命令使用方法

  • 申请GPIO(GPIOT_19)

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    # echo 465  > /sys/class/gpio/export

  • 配置GPIO(GPIOT_19)为输出模式

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    # echo out > /sys/class/gpio/gpio465/direction

  • 设置GPIO(GPIOT_19)输出为高电平

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    # echo 1 >  /sys/class/gpio/gpio465/value

  • 设置GPIO(GPIOT_19)输出为低电平

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    # echo 0 >  /sys/class/gpio/gpio465/value

  • 配置GPIO(GPIOT_19)为输入模式

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    # echo in > /sys/class/gpio/gpio465/direction

  • 读取GPIO(GPIOT_19)电平

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    # cat /sys/class/gpio/gpio465/value

  • 释放GPIO(GPIOT_19)

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    # echo 465 > /sys/class/gpio/unexport

JAVA应用使用方法

  • 获取root权限

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    Process mProcess = Runtime.getRuntime().exec("su");

  • 申请GPIO(GPIOT_19)

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    DataOutputStream os = new DataOutputStream(mProcess.getOutputStream());
    os.writeBytes("echo " + 465 + " > /sys/class/gpio/export\n");

  • 配置GPIO(GPIOT_19)为输出模式

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    os.writeBytes("echo out > /sys/class/gpio/gpio" + 465 + "/direction\n");

  • 设置GPIO(GPIOT_19)输出为高电平

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    os.writeBytes("echo 1 > /sys/class/gpio/gpio" + 465 + "/value\n");

  • 配置GPIO(GPIOT_19)为输入模式

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    os.writeBytes("echo in > /sys/class/gpio/gpio" + 465 + "/direction\n");

  • 读取GPIO(GPIOT_19)电平

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    Runtime runtime = Runtime.getRuntime(); 
    Process process = runtime.exec("cat " + "/sys/class/gpio/gpio" + 465 + "/value");  
    InputStream is = process.getInputStream(); 
    InputStreamReader isr = new InputStreamReader(is); 
    BufferedReader br = new BufferedReader(isr); 
    String line ; 
    while (null != (line = br.readLine())) { 
     return Integer.parseInt(line.trim()); 
    }

  • 释放GPIO(GPIOT_19)

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    os.writeBytes("echo " + 465 + " > /sys/class/gpio/unexport\n");