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1、前言

本来是没有这篇文章的。最近在rk3576下调试ec11旋转编码器时，一直没有效果，或者一开始可以，之后又不行了。首先我使用的ec11是基于AB相输出的，其次rk3576连接到AB相的引脚不是原生IO脚，是通过xl9535 gpio扩展芯片连接的，关于bug的调试可以参考《Linux下xl9535 gpio扩展芯片bug调试》。本文介绍基于原生IO引脚的ec11旋转编码器调试，总共有两种方式，一种是基于gpio-keys驱动，一种基于rotary-encoder驱动，这两个驱动都是内核自带的。

2、使用gpio-keys驱动

gpio-keys是按键驱动。所以使用此种方法只是把A相和B相的输出分别当作一个按键，并注册进input子系统。最终是在应用层实现驱动。

2.1、dts配置

# ec11的按键
Rotary_SW {compatible = "gpio-keys";status = "okay";#address-cells = <1>;#size-cells = <0>;rotary_sw {label = "rotary_sw";linux,code=<KEY_0>;debounce-interval = <5>;gpios = <&gpio3 6 GPIO_ACTIVE_LOW>;interrupt-parent = <&gpio3>;interrupts = <6 IRQ_TYPE_LEVEL_LOW>;};
};Rotary_A {compatible = "gpio-keys";status = "okay";#address-cells = <1>;#size-cells = <0>;rotary_a {label = "rotary_a";linux,code=<250>;debounce-interval = <1>;gpios = <&gpio4 RK_PA6 GPIO_ACTIVE_HIGH>;interrupt-parent = <&gpio4>;interrupts = <6 IRQ_TYPE_EDGE_RISING>;};
};Rotary_B {compatible = "gpio-keys";status = "okay";#address-cells = <1>;#size-cells = <0>;rotary_b {label = "rotary_b";linux,code=<251>;debounce-interval = <1>;gpios = <&gpio4 RK_PA4 GPIO_ACTIVE_HIGH>;interrupt-parent = <&gpio4>;interrupts = <4 IRQ_TYPE_EDGE_RISING>;};
};

属性含义可参考：https://www.kernel.org/doc/Documentation/devicetree/bindings/input/gpio-keys.txt

2.2、识别原理

A相和B相输出的信号存在90度的相位差。当编码器顺时针旋转时，A相的信号会比B相的信号超前90度；而当编码器逆时针旋转时，A相的信号会比B相的信号滞后90度。

当检测到A相从低电平变为高电平时，如果此时B相为低电平，则编码器顺时针旋转：

当检测到B相从低电平变为高电平时，如果此时A相为低电平，则编码器逆时针旋转：

2.3、应用层驱动实现

#include <stdio.h>  
#include <stdlib.h>  
#include <fcntl.h>  
#include <unistd.h>  
#include <string.h>  
#include <linux/input.h>  
#include <pthread.h>  
#include <errno.h>  
#include <signal.h>#define EC11_SW_EVENT   "/dev/input/event7"  
#define EC11_A_EVENT    "/dev/input/event6"  
#define EC11_B_EVENT    "/dev/input/event5"  // 线程ID
pthread_t ec11_sw_obj, ec11_a_obj, ec11_b_obj;  // 文件描述符
int ec11_sw_fd, ec11_a_fd, ec11_b_fd;
int count = 0;                                      // 累计步数// 编码器状态变量
int ec11_sw_value = 0;  
int ec11_a_value = 1;  
int ec11_b_value = 1;  
int ec11_direction = 0;                             // 0:不动作 1:顺时针旋转 2:逆时针旋转 3:按键按下顺时针旋转 4:按键按下逆时针旋转 5:按键按下
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;   void sigint_handler(int sig_num) 
{    pthread_cancel(ec11_sw_obj);pthread_cancel(ec11_a_obj);pthread_cancel(ec11_b_obj);close(ec11_sw_fd);      close(ec11_a_fd);close(ec11_a_fd);pthread_join(ec11_sw_obj, NULL);pthread_join(ec11_a_obj, NULL);pthread_join(ec11_b_obj, NULL);printf("all thread exit\n");exit(0);  
}void *ec11_scan_thread(void *arg) 
{  int fd = *(int*)arg;                          struct input_event ie;      while (1) {  if (read(fd, &ie, sizeof(struct input_event)) == sizeof(struct input_event)) {  if (ie.type == EV_KEY) {  pthread_mutex_lock(&lock);      // 处理按键事件if (fd == ec11_sw_fd && ie.code == 4) {  ec11_sw_value = ie.value;  if (ec11_sw_value == 1 && ec11_a_value == 1 && ec11_b_value == 1)   // 按键按下ec11_direction = 5;  } // 处理A相事件else if (fd == ec11_a_fd && ie.code == 250) {  if (ie.value == 0 && ec11_b_value == 1)             // 顺时针旋转{  ec11_a_value = 0;  ec11_direction = (ec11_sw_value == 1) ? 3 : 1;  // 判断按键状态  } else if (ie.value == 1) ec11_a_value = 1;  } // 处理B相事件else if (fd == ec11_b_fd && ie.code == 251) {  if (ie.value == 0 && ec11_a_value == 1)             // 逆时针旋转{  ec11_b_value = 0;  ec11_direction = (ec11_sw_value == 1) ? 4 : 2;  // 判断按键状态  } else if (ie.value == 1) ec11_b_value = 1;  }  pthread_mutex_unlock(&lock);   }  }  }   
}  int main(int argc, char **argv) 
{  int ret;ec11_sw_fd = open(EC11_SW_EVENT, O_RDONLY);  ec11_a_fd = open(EC11_A_EVENT, O_RDONLY);  ec11_b_fd = open(EC11_B_EVENT, O_RDONLY);  if (ec11_sw_fd < 0 || ec11_a_fd < 0 || ec11_b_fd < 0) {  printf("Failed to open input device\n");  return -1;  }pthread_create(&ec11_sw_obj, NULL, ec11_scan_thread, &ec11_sw_fd);  pthread_create(&ec11_a_obj, NULL, ec11_scan_thread, &ec11_a_fd);  pthread_create(&ec11_b_obj, NULL, ec11_scan_thread, &ec11_b_fd);  signal(SIGINT, sigint_handler);         // 注册信号处理函数                                         while (1) {  pthread_mutex_lock(&lock);          switch (ec11_direction)             {  case 1: count++;printf("顺时针转 : %d\n", count); break;  case 2: count--;printf("逆时针转 : %d\n", count); break;  case 3: count++;printf("按键按下顺时针转 : %d\n", count); break;  case 4: count--;printf("按键按下逆时针转 : %d\n", count); break;  case 5: printf("按键按下\n"); break;  default: break;  }  ec11_direction = 0;                 pthread_mutex_unlock(&lock);        usleep(10000); }  return 0;  
}

2.4、编译测试

# 如果使用buildroot系统，需要交叉编译。
# 这里使用的是ubuntu系统，直接使用gcc编译。
gcc -o build ec11.c

3、使用rotary-encoder驱动

rotary-encoder驱动是一个在内核态实现旋转编码器驱动。可以输出相对位置或者绝对位置，以下以输出相对位置举例。最终也是注册进input子系统。

3.1、dts配置

rotary@0 {compatible = "rotary-encoder"; gpios = <&gpio4 RK_PA6 GPIO_ACTIVE_HIGH>, <&gpio4 RK_PA4 GPIO_ACTIVE_HIGH>;linux,axis = <0>; /* REL_X */rotary-encoder,encoding = "gray";rotary-encoder,relative-axis;interrupt-parent = <&gpio4>;pinctrl-names = "default";pinctrl-0 = <&pinctrl_rotary>;
};&pinctrl {rotary {pinctrl_rotary:pinctrl_rotary {rockchip,pins = <4 RK_PA6 RK_FUNC_GPIO &pcfg_pull_none4 RK_PA4 RK_FUNC_GPIO &pcfg_pull_none>;};};
}

属性含义可参考：https://www.kernel.org/doc/Documentation/devicetree/bindings/input/rotary-encoder.txt

3.2、app测试程序编写

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/input.h>int main(int argc, char *argv[])
{struct input_event ie;int fd;if (argc != 2) {fprintf(stderr, "usage: %s <input-dev>\n", argv[0]);exit(-1);}fd = open(argv[1], O_RDONLY);if (fd < 0) {fprintf(stderr, "can not open %s\n", argv[1]);exit(-1);}while (1){if (read(fd, &ie, sizeof(struct input_event)) == sizeof(struct input_event))printf("type:%d code:%d value:%d\n", ie.type, ie.code, ie.value);}
}

3.3、编译测试

# 如果使用buildroot系统，需要交叉编译。
# 这里使用的是ubuntu系统，直接使用gcc编译。
gcc -o build ec11_app.c

4、总结

参考文章：

Linux 输入设备调试详解（零基础开发）Rotary_Encoder旋转编码器驱动（EC11）通用GPIO为例 挂载input输入子系统_rotary encoder with display-CSDN博客