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¶

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_MODE 和 LEDC_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；
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；
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；
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¶

motor/servo/include/iot_servo.h

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

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