LowLevel SDK API Definition

1. LowLevel Data Structures and Function Descriptions

lowlevel.h file defines the robot's low-level motor control interface, mainly implemented through shared memory (SHM) to manage robot motor control and status, as well as inertial measurement unit (IMU) data sharing.

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1.1 Data Structures

1.1.1 Joint Control Parameters

Structure Prototype

typedef struct joint_control_def {
    float p_des; // Target position (unit: radians)
    float v_des; // Target velocity (unit: radians/second)
    float kp;    // Proportional gain
    float kd;    // Derivative gain
    float t_ff;  // Feedforward torque (unit: Newton·meters)
} joint_control_t;

Field Description

Field Name	Type	Description
p_des	float	Target position, unit in radians
v_des	float	Target velocity, unit in radians/second
kp	float	Proportional gain, used in controller
kd	float	Derivative gain, used in controller
t_ff	float	Feedforward torque, unit in Newton·meters

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1.1.2 Leg Control Parameters

Structure Prototype

typedef struct leg_control_def {
    joint_control_t abad; // Hip joint abduction/adduction control
    joint_control_t hip;  // Hip joint pitch control
    joint_control_t knee; // Knee joint control
    joint_control_t foot; // Foot control
    int32_t flags;        // Flag bits, always set to 1
} leg_control_t;

Field Description

Field Name	Type	Description
abad	joint_control_t	Hip joint abduction/adduction control parameters
hip	joint_control_t	Hip joint pitch control parameters
knee	joint_control_t	Knee joint control parameters
foot	joint_control_t	Foot control parameters
flags	int32_t	Flag bits, always set to 1

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1.1.3 Joint State Parameters

Structure Prototype

typedef struct joint_state_def {
    int32_t flags; // Status flag bits
    float p;       // Current angle (unit: radians)
    float v;       // Current angular velocity (unit: radians/second)
    float t;       // Current torque (unit: Newton·meters)
} joint_state_t;

Field Description

Field Name	Type	Description
flags	int32_t	Status flag bits, contains motor status information
p	float	Current angle, unit in radians
v	float	Current angular velocity, unit in radians/second
t	float	Current torque, unit in Newton·meters

Remarks

• Each bit of flags represents different status information, such as voltage, temperature, fault flags, etc.

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1.1.4 Leg State Parameters

Structure Prototype

typedef struct leg_state_def {
    joint_state_t abad; // Hip joint abduction/adduction state
    joint_state_t hip;  // Hip joint pitch state
    joint_state_t knee; // Knee joint state
    joint_state_t foot; // Foot state
} leg_state_t;

Field Description

Field Name	Type	Description
abad	joint_state_t	Hip joint abduction/adduction state parameters
hip	joint_state_t	Hip joint pitch state parameters
knee	joint_state_t	Knee joint state parameters
foot	joint_state_t	Foot state parameters

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1.2 Function Interface

1.2.1 Create Leg Control Shared Memory

Function Prototype

static inline spline_data_p create_spline_shm(void);

Function Overview Create shared memory for leg control and status.

Return Value

Return Value	Description
spline_data_p	Pointer to shared memory

Remarks

• Shared memory path is /spline_shm.
• Shared memory size is 10 KB.

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1.2.2 Destroy Leg Control Shared Memory

Function Prototype

static inline void destroy_spline_shm(spline_data_p ptr);

Function Overview Destroy shared memory for leg control and status.

Parameter Description

Parameter Name	Type	Description
ptr	spline_data_p	Pointer to shared memory

Remarks

• No need to explicitly unmap or delete shared memory in current implementation.

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1.2.3 Create IMU Data Shared Memory

Function Prototype

static inline nav_imu_p create_imu_shm(void);

Function Overview Create shared memory for IMU data.

Return Value

Return Value	Description
nav_imu_p	Pointer to shared memory

Remarks

• Shared memory path is /imu_shm.
• Shared memory size is 1 KB.

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1.2.4 Destroy IMU Data Shared Memory

Function Prototype

static inline void destroy_imu_shm(nav_imu_p ptr);

Function Overview Destroy shared memory for IMU data.

Parameter Description

Parameter Name	Type	Description
ptr	nav_imu_p	Pointer to shared memory

Remarks

• No need to explicitly unmap or delete shared memory in current implementation.

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1.3 Notes

Shared Memory Management

• Ensure shared memory is properly destroyed when the program exits.
• Pay attention to synchronization issues when multiple processes access shared memory.

Parameter Range

• Parameters in joint_control_t (such as kp, kd) need to be set to reasonable ranges according to specific hardware characteristics.
• Status values in joint_state_t (such as p, v, t) may be limited by hardware.

Real-time Requirements

• Shared memory update frequency is 1 ms, ensure consumers can process data in time.

Data Read/Write

• CONSUMER_CONTROL is the status bit,
  • When controlling, the consumer sets the status to 1, and the producer reads the data and sets the status to 0.
  • When reading data, the producer sets the status to 1, and the consumer reads the data and sets the status to 0.

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