舵机

[English]

该组件使用 LEDC 外设产生 PWM 信号,可以实现对最多 16 路舵机的独立控制(ESP32 支持 16 路通道,ESP32-S2 支持 8 路通道),控制频率可选择为 50 ~ 400 Hz。使用该层 API,用户只需要指定舵机所在组、通道和目标角度,即可实现对舵机的角度操作。

舵机内部一般存在一个产生固定周期和脉宽的基准信号,通过与输入 PWM 信号进行比较,获得电压差输出,进而控制电机的转动方向和转动角度。常见的 180 度角旋转舵机一般以 20 ms (50 Hz) 为时钟周期,通过 0.5 ~ 2.5 ms 高电平脉冲,对应控制舵机在 0 ~ 180 度之间转动。

该组件可用于对控制精度要求较低的场景,例如玩具小车、遥控机器人、家庭自动化等。

使用方法

  1. 舵机初始化:使用 servo_init() 对一组通道进行初始化,ESP32 包含 LEDC_LOW_SPEED_MODELEDC_HIGH_SPEED_MODE 两组通道,有些芯片可能只支持一组。初始化配置项主要包括最大角度、信号频率、最小输入脉宽和最大输入脉宽,用于计算角度和占空比的对应关系;引脚和通道用于分别指定芯片引脚和 LEDC 通道的对应关系;

  2. 设置目标角度:使用 servo_write_angle() 通过指定舵机所在组、所在通道和目标角度,对舵机角度进行控制;

  3. 读取当前角度:可使用 servo_read_angle() 获取舵机当前角度,需要注意的是该角度是根据输入信号进行推算的理论角度;

  4. 舵机去初始化:当一组多个舵机都不再使用时,可使用 servo_deinit() 对一组通道进行去初始化。

应用示例

servo_config_t servo_cfg = {
    .max_angle = 180,
    .min_width_us = 500,
    .max_width_us = 2500,
    .freq = 50,
    .timer_number = LEDC_TIMER_0,
    .channels = {
        .servo_pin = {
            SERVO_CH0_PIN,
            SERVO_CH1_PIN,
            SERVO_CH2_PIN,
            SERVO_CH3_PIN,
            SERVO_CH4_PIN,
            SERVO_CH5_PIN,
            SERVO_CH6_PIN,
            SERVO_CH7_PIN,
        },
        .ch = {
            LEDC_CHANNEL_0,
            LEDC_CHANNEL_1,
            LEDC_CHANNEL_2,
            LEDC_CHANNEL_3,
            LEDC_CHANNEL_4,
            LEDC_CHANNEL_5,
            LEDC_CHANNEL_6,
            LEDC_CHANNEL_7,
        },
    },
    .channel_number = 8,
} ;
iot_servo_init(LEDC_LOW_SPEED_MODE, &servo_cfg);

float angle = 100.0f;

// Set angle to 100 degree
iot_servo_write_angle(LEDC_LOW_SPEED_MODE, 0, angle);

// Get current angle of servo
iot_servo_read_angle(LEDC_LOW_SPEED_MODE, 0, &angle);

//deinit servo
iot_servo_deinit(LEDC_LOW_SPEED_MODE);

API 参考

Header File

Functions

esp_err_t iot_servo_init(ledc_mode_t speed_mode, const servo_config_t *config)

Initialize ledc to control the servo.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

  • ESP_FAIL Configure ledc failed

Parameters
  • speed_mode: Select the LEDC channel group with specified speed mode. Note that not all targets support high speed mode.

  • config: Pointer of servo configure struct

esp_err_t iot_servo_deinit(ledc_mode_t speed_mode)

Deinitialize ledc for servo.

Return

  • ESP_OK Success

Parameters
  • speed_mode: Select the LEDC channel group with specified speed mode.

esp_err_t iot_servo_write_angle(ledc_mode_t speed_mode, uint8_t channel, float angle)

Set the servo motor to a certain angle.

Note

This API is not thread-safe

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • speed_mode: Select the LEDC channel group with specified speed mode.

  • channel: LEDC channel, select from ledc_channel_t

  • angle: The angle to go

esp_err_t iot_servo_read_angle(ledc_mode_t speed_mode, uint8_t channel, float *angle)

Read current angle of one channel.

Return

  • ESP_OK Success

  • ESP_ERR_INVALID_ARG Parameter error

Parameters
  • speed_mode: Select the LEDC channel group with specified speed mode.

  • channel: LEDC channel, select from ledc_channel_t

  • angle: Current angle of the channel

Structures

struct servo_channel_t

Configuration of servo motor channel.

Public Members

gpio_num_t servo_pin[LEDC_CHANNEL_MAX]

Pin number of pwm output

ledc_channel_t ch[LEDC_CHANNEL_MAX]

The ledc channel which used

struct servo_config_t

Configuration of servo motor.

Public Members

uint16_t max_angle

Servo max angle

uint16_t min_width_us

Pulse width corresponding to minimum angle, which is usually 500us

uint16_t max_width_us

Pulse width corresponding to maximum angle, which is usually 2500us

uint32_t freq

PWM frequency

ledc_timer_t timer_number

Timer number of ledc

servo_channel_t channels

Channels to use

uint8_t channel_number

Total channel number