之前做過(guò)一個(gè)LED調(diào)光的項(xiàng)目，這次想拿XR806來(lái)實(shí)現(xiàn)，后續(xù)打算加入遠(yuǎn)程控制的功能。這個(gè)項(xiàng)目使用旋轉(zhuǎn)編碼器來(lái)調(diào)節(jié)LED的亮度，基本原理是MCU識(shí)別編碼器的旋轉(zhuǎn)方向和步數(shù)，調(diào)節(jié)PWM輸出占空比，從而實(shí)現(xiàn)亮度調(diào)節(jié)。

識(shí)別其旋轉(zhuǎn)方向和步數(shù)，要考慮消除抖動(dòng)，否則會(huì)出現(xiàn)識(shí)別錯(cuò)誤，導(dǎo)致系統(tǒng)不穩(wěn)定，這和按鍵是類似的。

Github上有對(duì)應(yīng)的Arduino庫(kù)，注意它的開(kāi)源協(xié)議是GNU GPL V3！本人曾經(jīng)移植到STM32，現(xiàn)已移植到XR806，效果良好。旋轉(zhuǎn)編碼器相關(guān)代碼如下：

頭文件re.h源碼：

/*
 * Rotary encoder library for Arduino.
 * Port to XR806 by Zixun Chen.
 */

#ifndef _ROTARY_ENCODER_H_
#define _ROTARY_ENCODER_H_

#ifdef __cplusplus
extern "C" {
#endif

#include "main.h"

// 根據(jù)編碼器的輸出類型來(lái)選擇是否定義RE_HALF_STEP
#define RE_HALF_STEP

// 旋轉(zhuǎn)編碼器通常外接上拉電阻，對(duì)應(yīng)空閑電平是00B。如果外接電阻是下拉的，需要定義RE_PINS_PULL_DOWN
// #define RE_PINS_PULL_DOWN

#define DIR_NONE 0    // 尚無(wú)完整有效的步進(jìn)
#define DIR_CW   0x10 // 順時(shí)針步進(jìn)
#define DIR_CCW  0x20 // 逆時(shí)針步進(jìn)

typedef struct {
    // 定義編碼器A端所連的GPIO引腳
    GPIO_Port GPIO_A;
    GPIO_Pin PIN_A;
    // 定義編碼器B端所連的GPIO引腳
    GPIO_Port GPIO_B;
    GPIO_Pin PIN_B;
    uint8_t RetVal; // 保存返回值
    uint8_t State; // 內(nèi)部變量，保存狀態(tài)機(jī)狀態(tài)
} REHandle_t;

void RotaryEncoderInit(REHandle_t *REVal); // 初始化
void RotaryEncoderProcess(REHandle_t *REVal); // 讀取步進(jìn)

#ifdef __cplusplus
}
#endif

#endif // _ROTARY_ENCODER_H_

源文件re.c：

/* Rotary encoder handler for arduino.
 *
 * Copyright 2011 Ben Buxton. Licenced under the GNU GPL Version 3.
 * Contact: bb@cactii.net
 *
 * Port to XR806 by Zixun Chen.
 */

#include "re.h"

/*
 * The below state table has, for each state (row), the new state
 * to set based on the next encoder output. From left to right in,
 * the table, the encoder outputs are 00, 01, 10, 11, and the value
 * in that position is the new state to set.
 */

#define R_START 0x0

#ifdef RE_HALF_STEP
// Use the half-step state table (emits a code at 00 and 11)
#define R_CCW_BEGIN 0x1
#define R_CW_BEGIN 0x2
#define R_START_M 0x3
#define R_CW_BEGIN_M 0x4
#define R_CCW_BEGIN_M 0x5
const unsigned char ttable[6][4] = {
    // R_START (00)
    {R_START_M,           R_CW_BEGIN,    R_CCW_BEGIN,  R_START},
    // R_CCW_BEGIN
    {R_START_M | DIR_CCW, R_START,       R_CCW_BEGIN,  R_START},
    // R_CW_BEGIN
    {R_START_M | DIR_CW,  R_CW_BEGIN,    R_START,      R_START},
    // R_START_M (11)
    {R_START_M,           R_CCW_BEGIN_M, R_CW_BEGIN_M, R_START},
    // R_CW_BEGIN_M
    {R_START_M,           R_START_M,     R_CW_BEGIN_M, R_START | DIR_CW},
    // R_CCW_BEGIN_M
    {R_START_M,           R_CCW_BEGIN_M, R_START_M,    R_START | DIR_CCW},
};
#else
// Use the full-step state table (emits a code at 00 only)
#define R_CW_FINAL 0x1
#define R_CW_BEGIN 0x2
#define R_CW_NEXT 0x3
#define R_CCW_BEGIN 0x4
#define R_CCW_FINAL 0x5
#define R_CCW_NEXT 0x6

const unsigned char ttable[7][4] = {
  // R_START
  {R_START,    R_CW_BEGIN,  R_CCW_BEGIN, R_START},
  // R_CW_FINAL
  {R_CW_NEXT,  R_START,     R_CW_FINAL,  R_START | DIR_CW},
  // R_CW_BEGIN
  {R_CW_NEXT,  R_CW_BEGIN,  R_START,     R_START},
  // R_CW_NEXT
  {R_CW_NEXT,  R_CW_BEGIN,  R_CW_FINAL,  R_START},
  // R_CCW_BEGIN
  {R_CCW_NEXT, R_START,     R_CCW_BEGIN, R_START},
  // R_CCW_FINAL
  {R_CCW_NEXT, R_CCW_FINAL, R_START,     R_START | DIR_CCW},
  // R_CCW_NEXT
  {R_CCW_NEXT, R_CCW_FINAL, R_CCW_BEGIN, R_START},
};
#endif

static uint8_t ReadPinLevel(GPIO_Port GPIOx, GPIO_Pin PINy); // 內(nèi)部函數(shù)，讀取引腳電平

void RotaryEncoderInit(REHandle_t *REVal) {
    GPIO_InitParam GPIO_InitVal={0};
    // 初始化GPIO引腳
    GPIO_InitVal.driving=GPIO_DRIVING_LEVEL_1;
    GPIO_InitVal.mode=GPIOx_Pn_F0_INPUT;
    GPIO_InitVal.pull=GPIO_PULL_NONE;
    HAL_GPIO_Init(REVal- >GPIO_A, REVal- >PIN_A, &GPIO_InitVal);
    HAL_GPIO_Init(REVal- >GPIO_B, REVal- >PIN_B, &GPIO_InitVal);
    // 初始化狀態(tài)機(jī)
    REVal- >State=R_START;
}

void RotaryEncoderProcess(REHandle_t *REVal) {
    uint8_t pinstate;
    // 讀取AB端電平
    pinstate=(ReadPinLevel(REVal- >GPIO_B, REVal- >PIN_B)< 1) | 
              ReadPinLevel(REVal- >GPIO_A, REVal- >PIN_A);
    // 狀態(tài)機(jī)操作
    REVal- >State=ttable[REVal- >State & 0xf][pinstate];
    // 返回編碼器步進(jìn)信息
    REVal- >RetVal=REVal- >State & 0x30;
}

static uint8_t ReadPinLevel(GPIO_Port GPIOx, GPIO_Pin PINy)
{
    GPIO_PinState RDPin;
    RDPin=HAL_GPIO_ReadPin(GPIOx, PINy);
    #ifdef RE_PINS_PULL_DOWN
    // 如果定義RE_PINS_PULL_DOWN，需要反轉(zhuǎn)引腳電平
    if(GPIO_PIN_HIGH==RDPin) {
        return 0;
    } else {
        return 1;
    }
    #else // RE_PINS_PULL_DOWN
    if(GPIO_PIN_HIGH==RDPin) {
        return 1;
    } else {
        return 0;
    }
    #endif // RE_PINS_PULL_DOWN
}

編碼器A端和B端分別連接PA12和PA13，使用板載LED即可，引腳是PA21，對(duì)應(yīng)PWM_CH2。開(kāi)發(fā)環(huán)境基于FreeRTOS，XR806 SDK在 ~/tools/目錄下。在 ~/tools/xr806_sdk/project/demo/ 目錄下新建 tryre 文件夾，并在其中添加源代碼，makefile等文件，然后按照教程編譯鏈接下載即可。主要代碼如下：
頭文件main.h：

#ifndef __MAIN_H
#define __MAIN_H

#ifdef __cplusplus
extern "C" {
#endif

// 需要包含的頭文件
#include < stdio.h >
#include "driver/chip/hal_gpio.h"
#include "driver/chip/hal_pwm.h"
#include "re.h"
#include "FreeRTOS.h"
#include "task.h"

#ifdef __cplusplus
}
#endif

#endif /* __MAIN_H */

main.c：

#include "main.h"

// 定義編碼器占用的GPIO引腳
static REHandle_t REVal={
    .GPIO_A=GPIO_PORT_A,
    .PIN_A=GPIO_PIN_12,
    .GPIO_B=GPIO_PORT_A,
    .PIN_B=GPIO_PIN_13
};
static const uint8_t STEPMAX=10, STEPMIN=0;
static uint8_t step=0; // 控制LED亮度等級(jí)
static void RotaryScan(void); // 編碼器識(shí)別與處理
// PWM輸出初始化
#define PWM_CHANNEL   PWM_GROUP1_CH2
#define PWM_MODE      PWM_CYCLE_MODE
#define PWM_GPIO_PORT GPIO_PORT_A
#define PWM_GPIO_PIN  GPIO_PIN_21
#define PWM_GPIO_MODE GPIOA_P21_F4_PWM2_ECT2
static int max_duty_ratio; // PWM計(jì)數(shù)上限
static void PWMCycleModeSet(void); // PWM重復(fù)輸出模式初始化
static HAL_Status PWMDutyRatioSet(int val); // 設(shè)置PWM輸出占空比
// FreeRTOS配置
#define TASK_RE_PRIO     1
#define TASK_RE_STK_SIZE 200
static TaskHandle_t TaskRE_Handler=NULL;
static void TaskCreation(void); // 創(chuàng)建任務(wù)
static void TaskRE(void *pvParameters); // 編碼器識(shí)別任務(wù)

int main(void)
{
    printf("Rotary encoder & PWM demo.rn"); // 串口輸出相關(guān)信息
    RotaryEncoderInit(&REVal); // 初始化編碼器
    PWMCycleModeSet(); // 初始化PWM
    PWMDutyRatioSet(max_duty_ratio*step/STEPMAX); // 設(shè)置PWM輸出占空比
    TaskCreation(); // 創(chuàng)建任務(wù)
    // 任務(wù)調(diào)度不需要用戶指定
    return 0;
}

static void TaskCreation(void)
{
    BaseType_t xRet = NULL;
    taskENTER_CRITICAL();
    xRet = xTaskCreate((TaskFunction_t )TaskRE, (const char *)"TaskRE", (uint16_t)TASK_RE_STK_SIZE, 
                       (void *)NULL, (UBaseType_t)TASK_RE_PRIO, (TaskHandle_t *)&TaskRE_Handler);
    if(pdPASS == xRet) {
        printf("TaskRE created!rn"); // 任務(wù)創(chuàng)建成功
    }
    taskEXIT_CRITICAL();
}

static void TaskRE(void *pvParameters)
{
    while (1) {
        RotaryScan(); // 識(shí)別編碼器步進(jìn)
        vTaskDelay(10); // 延遲10（ms）
    }
}

static void RotaryScan(void)
{
    RotaryEncoderProcess(&REVal); // 識(shí)別編碼器步進(jìn)
    if(DIR_CW == REVal.RetVal) { // 順時(shí)針步進(jìn)
        if(step< STEPMAX) {
            step++; // 增大亮度，上限是STEPMAX
            PWMDutyRatioSet(max_duty_ratio*step/STEPMAX);
            printf("%d  ", step);
        }
    } else if(DIR_CCW == REVal.RetVal) {
        if(step >STEPMIN) {
            step--; // 減小亮度，下限是STEPMIN
            PWMDutyRatioSet(max_duty_ratio*step/STEPMAX);
            printf("%d  ", step);
        }
    }
}

static void PWMCycleModeSet(void)
{
    // 初始化硬件所需變量聲明
    GPIO_InitParam io_param = {0};
    HAL_Status status = HAL_ERROR;
    PWM_ClkParam clk_param = {0};
    PWM_ChInitParam ch_param = {0};
    // 配置GPIO復(fù)用，官方例程里面缺了這一部分
    io_param.driving = GPIO_DRIVING_LEVEL_1;
    io_param.mode = PWM_GPIO_MODE;
    io_param.pull = GPIO_PULL_NONE;
    HAL_GPIO_Init(PWM_GPIO_PORT, PWM_GPIO_PIN, &io_param);
    // 配置PWM時(shí)鐘源
    clk_param.clk = PWM_CLK_HOSC;
    clk_param.div = PWM_SRC_CLK_DIV_1;
    status = HAL_PWM_GroupClkCfg(PWM_CHANNEL / 2, &clk_param);
    if (status != HAL_OK) {
        printf("%s(): %d, PWM group clk config errorn", __func__, __LINE__);
    }
    // 配置PWM模式，頻率和極性
    ch_param.hz = 1000;
    ch_param.mode = PWM_MODE;
    ch_param.polarity = PWM_HIGHLEVE;
    max_duty_ratio = HAL_PWM_ChInit(PWM_CHANNEL, &ch_param);
    if (max_duty_ratio == -1) {
        printf("%s(): %d, PWM ch init errorn", __func__, __LINE__);
    }
    // 設(shè)置占空比
    status = HAL_PWM_ChSetDutyRatio(PWM_CHANNEL, max_duty_ratio / 2);
    if (status != HAL_OK) {
        printf("%s(): %d, PWM set duty ratio errorn", __func__, __LINE__);
    }
    // 使能通道
    status = HAL_PWM_EnableCh(PWM_CHANNEL, PWM_MODE, 1);
    if (status != HAL_OK) {
        printf("%s(): %d, PWM ch enable errorn", __func__, __LINE__);
    }
}

static HAL_Status PWMDutyRatioSet(int val)
{
    return HAL_PWM_ChSetDutyRatio(PWM_CHANNEL, val);
}