content_views"
class="markdown_views prism-atom-one-dark">
前言
本文简单介绍了class="tags" href="/LongXin.html" title=龙芯>龙芯class="tags" href="/2K1000.html" title=2k1000>2k1000中的GPIO控制。
1. 头文件引入
<code class="prism language-c">class="token macro property">class="token directive-hash">#class="token directive keyword">include class="token string"><stdio.h> class="token comment">// 标准输入输出函数（如snprintf）
class="token macro property">class="token directive-hash">#class="token directive keyword">include class="token string"><stdlib.h> class="token comment">// 系统调用函数（如system）
class="token macro property">class="token directive-hash">#class="token directive keyword">include class="token string"><time.h> class="token comment">// 时间相关函数
class="token macro property">class="token directive-hash">#class="token directive keyword">include class="token string"><unistd.h> class="token comment">// POSIX操作系统API（如文件操作）
class="token macro property">class="token directive-hash">#class="token directive keyword">include class="token string"><fcntl.h> class="token comment">// 文件控制选项（如open的flags）
class="token macro property">class="token directive-hash">#class="token directive keyword">include class="token string"><sys/mman.h> class="token comment">// 内存映射相关函数
class="token macro property">class="token directive-hash">#class="token directive keyword">include class="token string">"GPIO.h" class="token comment">// 自定义GPIO相关声明（可能包含常量或宏）
code>
作用
ckquote> 作用：引入必要的库和头文件c;支持文件操作、字符串格式化等功能。
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GPIO_export_gpio_32">2. 导出GPIO引脚 export_gpio
<code class="prism language-c">class="token keyword">void class="token function">export_gpioclass="token punctuation">(class="token keyword">int gpioclass="token punctuation">) class="token punctuation">{class="token keyword">char commandclass="token punctuation">[class="token number">100class="token punctuation">]class="token punctuation">;class="token function">snprintfclass="token punctuation">(commandclass="token punctuation">, class="token keyword">sizeofclass="token punctuation">(commandclass="token punctuation">)class="token punctuation">, class="token string">"echo %d > /sys/class/gpio/export"class="token punctuation">, gpioclass="token punctuation">)class="token punctuation">;class="token function">systemclass="token punctuation">(commandclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
code>
功能
ckquote> 功能：通过写入/sys/class/gpio/export文件导出GPIO引脚。
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示例
示例：echo 1 > /sys/class/gpio/export 导出GPIO1。
注意
ckquote> 若GPIO已导出c;此操作会失败。
需添加错误检查（如检查文件是否存在）。
ckquote>
GPIO_set_gpio_direction_51">3. 设置GPIO方向 set_gpio_direction
<code class="prism language-c">class="token keyword">void class="token function">set_gpio_directionclass="token punctuation">(class="token keyword">int gpioclass="token punctuation">, class="token keyword">const class="token keyword">charclass="token operator">* directionclass="token punctuation">) class="token punctuation">{class="token keyword">char commandclass="token punctuation">[class="token number">100class="token punctuation">]class="token punctuation">;class="token function">snprintfclass="token punctuation">(commandclass="token punctuation">, class="token keyword">sizeofclass="token punctuation">(commandclass="token punctuation">)class="token punctuation">, class="token string">"echo \"%s\" > /sys/class/gpio/gpio%d/direction"class="token punctuation">, directionclass="token punctuation">, gpioclass="token punctuation">)class="token punctuation">;class="token function">systemclass="token punctuation">(commandclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
code>
功能
ckquote> 功能：设置GPIO为输入（“in”）或输出（“out”）。
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示例
ckquote> 示例：echo “out” > /sys/class/gpio/gpio1/direction 设置GPIO1为输出。
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GPIO_set_gpio_value_65">4. 设置GPIO值 set_gpio_value
<code class="prism language-c">class="token keyword">void class="token function">set_gpio_valueclass="token punctuation">(class="token keyword">int gpioclass="token punctuation">, class="token keyword">int valueclass="token punctuation">) class="token punctuation">{class="token keyword">char commandclass="token punctuation">[class="token number">100class="token punctuation">]class="token punctuation">;class="token function">snprintfclass="token punctuation">(commandclass="token punctuation">, class="token keyword">sizeofclass="token punctuation">(commandclass="token punctuation">)class="token punctuation">, class="token string">"echo \"%d\" > /sys/class/gpio/gpio%d/value"class="token punctuation">, valueclass="token punctuation">, gpioclass="token punctuation">)class="token punctuation">;class="token function">systemclass="token punctuation">(commandclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
code>
功能
ckquote> 功能：设置输出引脚的电平（0为低c;1为高）。
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示例
ckquote> 示例：echo 1 > /sys/class/gpio/gpio1/value 设置GPIO1为高电平。
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5. 初始化函数 gpio_init
<code class="prism language-c">class="token keyword">void class="token function">gpio_initclass="token punctuation">(class="token keyword">int gpioclass="token punctuation">, class="token keyword">const class="token keyword">charclass="token operator">* directionclass="token punctuation">, class="token keyword">int valueclass="token punctuation">) class="token punctuation">{class="token function">export_gpioclass="token punctuation">(gpioclass="token punctuation">)class="token punctuation">;class="token function">set_gpio_directionclass="token punctuation">(gpioclass="token punctuation">, directionclass="token punctuation">)class="token punctuation">;class="token function">set_gpio_valueclass="token punctuation">(gpioclass="token punctuation">, valueclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
code>
功能
ckquote> 功能：整合导出、方向设置和初始值设置的流程。
ckquote>
6.class="tags" href="/LongXin.html" title=龙芯>龙芯2K1000适配说明
ckquote> class="tags" href="/LongXin.html" title=龙芯>龙芯2K1000的GPIO可能按组（Bank）编号c;需查阅手册确认物理引脚与逻辑编号的对应关系。
ckquote>
ckquote> 示例：GPIO1可能对应硬件引脚PZ.1c;需参考《class="tags" href="/LongXin.html" title=龙芯>龙芯2K1000硬件手册》。
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6.2 性能优化建议
<code class="prism language-c">直接文件操作代替system：
class="token keyword">void class="token function">export_gpioclass="token punctuation">(class="token keyword">int gpioclass="token punctuation">) class="token punctuation">{class="token keyword">int fd class="token operator">= class="token function">openclass="token punctuation">(class="token string">"/sys/class/gpio/export"class="token punctuation">, O_WRONLYclass="token punctuation">)class="token punctuation">;class="token keyword">if class="token punctuation">(fd class="token operator">< class="token number">0class="token punctuation">) class="token punctuation">{ class="token comment">/* 错误处理 */ class="token punctuation">}class="token keyword">char bufclass="token punctuation">[class="token number">10class="token punctuation">]class="token punctuation">;class="token function">snprintfclass="token punctuation">(bufclass="token punctuation">, class="token keyword">sizeofclass="token punctuation">(bufclass="token punctuation">)class="token punctuation">, class="token string">"%d"class="token punctuation">, gpioclass="token punctuation">)class="token punctuation">;class="token function">writeclass="token punctuation">(fdclass="token punctuation">, bufclass="token punctuation">, class="token function">strlenclass="token punctuation">(bufclass="token punctuation">)class="token punctuation">)class="token punctuation">;class="token function">closeclass="token punctuation">(fdclass="token punctuation">)class="token punctuation">;
class="token punctuation">}
code>
优点
ckquote> 优点：避免启动Shell进程c;提升效率。
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错误处理
ckquote> 错误处理：检查文件操作返回值c;处理GPIO未导出或权限问题。
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6.3 权限问题
ckquote> 操作/sys/class/gpio需要root权限。
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解决方案
ckquote> 使用sudo运行程序。
配置udev规则c;允许普通用户访问GPIO设备。
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6.4内存映射（高级优化）
对于高频操作（如PWM）c;可通过内存映射直接操作GPIO寄存器：
<code class="prism language-c">class="token keyword">volatile class="token class-name">uint32_t class="token operator">*gpio_baseclass="token punctuation">;
class="token keyword">int fd class="token operator">= class="token function">openclass="token punctuation">(class="token string">"/dev/mem"class="token punctuation">, O_RDWRclass="token punctuation">)class="token punctuation">;
gpio_base class="token operator">= class="token function">mmapclass="token punctuation">(class="token constant">NULLclass="token punctuation">, PAGE_SIZEclass="token punctuation">, PROT_READclass="token operator">|PROT_WRITEclass="token punctuation">, MAP_SHAREDclass="token punctuation">, fdclass="token punctuation">, GPIO_BASE_ADDRclass="token punctuation">)class="token punctuation">;
class="token comment">// 直接读写寄存器：gpio_base[REG_OFFSET] |= (1 << PIN);
需查阅class="tags" href="/LongXin.html" title=龙芯>龙芯class="token number">2K1000的GPIO寄存器基地址和偏移量。
code>
6.5示例扩展：按键与LED控制
<code class="prism language-c">class="token keyword">int class="token function">mainclass="token punctuation">(class="token punctuation">) class="token punctuation">{class="token comment">// 初始化GPIO1（LED）为输出c;初始关闭class="token function">gpio_initclass="token punctuation">(class="token number">1class="token punctuation">, class="token string">"out"class="token punctuation">, class="token number">0class="token punctuation">)class="token punctuation">;class="token comment">// 初始化GPIO2（按键）为输入class="token function">gpio_initclass="token punctuation">(class="token number">2class="token punctuation">, class="token string">"in"class="token punctuation">, class="token number">0class="token punctuation">)class="token punctuation">;class="token keyword">whileclass="token punctuation">(class="token number">1class="token punctuation">) class="token punctuation">{class="token comment">// 读取按键状态（需实现read_gpio_value）class="token keyword">int key class="token operator">= class="token function">read_gpio_valueclass="token punctuation">(class="token number">2class="token punctuation">)class="token punctuation">;class="token comment">// 控制LEDclass="token function">set_gpio_valueclass="token punctuation">(class="token number">1class="token punctuation">, keyclass="token punctuation">)class="token punctuation">;class="token function">usleepclass="token punctuation">(class="token number">10000class="token punctuation">)class="token punctuation">; class="token comment">// 10ms防抖class="token punctuation">}class="token keyword">return class="token number">0class="token punctuation">;
class="token punctuation">}
code>
7.总结
适用场景
ckquote> 适用场景：简单GPIO控制（如LED、继电器）。
ckquote>
优势
ckquote> 优势：代码简洁c;依赖少c;易于移植。
ckquote>
局限性
ckquote> 局限性：system调用效率低c;缺少错误处理。
ckquote>
改进方向
ckquote> 改进方向：直接文件操作、内存映射寄存器、完善错误处理。
ckquote>
