Hardware

Objects in the hardware module ‘own’ a specific piece of hardware on the Beaglebone, and use the RAII principle to handle initialization and cleanup tasks. They provide a simpler interface of how to get/send information using the hardware

Inertial Measurement Unit - IMU

class Imu

Singleton class to communicate with the IMU. We use singleton because there is only one imu in hardware. This class utilizes the DMP (digital motion processor) on the MPU-9250 as a way to calculate orientation.

Public Functions

int init(const YAML::Node &config, uint32_t loop_frq, std::function<void(StateData&)> &func)

Initialize the Imu class.

Parameters:

config – YAML configuration for the Imu class
loop_frq – Desired sampling rate in Hz of the IMU
func – callback function to use when data is received

Returns:

0 on sucess, -1 on failure

Public Static Functions

static inline Imu &getInstance()

Get the Instance of the Imu object.

Returns:: Imu&

Programmable Realtime Unit - PRU

class PruRequester

The PruRequester is a class that helps handle the ownership of the programmable real-time unit (PRU) on the BeagleBone, which gives commands to ESCs/motors. It is critical that only one process is able to commands to the PRU at a time. Thus, this object creates a lockfile saved at ‘kPRU_LOCK_FILE’ to ensure that only one process can access the PRU at a time. On construction, the object will spawn a thread that continuously sends zero commands to the PRU. This prevents ESC’s from ‘chirping’ due to not receiving commands. The zero sender thread will run until ‘send_command’ is called, at which point it will stop the zero sender thread and send the new command. The zero sender thread can be restarted by calling ‘start_zero_sender’.

PruRequester::PruRequestor() - Construct the object and lock the PRU. Throw an exception if the lock fails.

PruRequester::send_command() - Sends a command to the PRU

Example usage is:

{
  PruRequester pru_requester;
  // The motors will be receiving zero commands until send_command is called
  while (in_control_loop) {
    std::array<float, 4> motor_commands{0.0, 0.0, 0.0, 0.0};
    if(!pru_requester.send_command(motor_commands)) {
      // handle error
    }
  }
 // Start the zero_sender thread again now the control loop is done
 pru_requester.start_zero_sender();
} // release the pru lock file on destruction

Public Functions

inline PruRequester(): Construct a new Pru Requester object.

inline bool send_command(const std::vector<float> &motor_commands)

Sends commands to ESCs, and stops the zero sender thread if it is running.

Parameters:: motor_commands – commands in the range [0, 1] to send to the ESCs
Returns:: true on success
Returns:: false on failure

Setpoint Module

class Setpoint

Setpoint class. Communicates with the remote control (using robotics_cape rc_dsm interface) to receive commands. Commands are: throttle, roll, pitch, yaw, kill_switch, and Aux_switch. Switches have binary information.

Public Functions

Setpoint(FlightMode flight_mode, std::array<float, 3> max_setpts_stabilized, std::array<float, 3> max_setpts_acro, std::array<float, 2> throttle_limits)

Construct a new Setpoint object.

Parameters:

flight_mode – flight mode: stabilized or acro
max_setpts_stabilized – max setpoints for stabilized mode (in RPW rad, rad, rad/s)
max_setpts_acro – max setpoints for acro mode (in RPW rad/s, rad/s, rad/s)
throttle_limits – The min (index 0) and max (index 1) throttle values between 0-1

Setpoint(FlightMode flight_mode, const YAML::Node &config_params)

Construct a new Setpoint object using a yaml node. The node must have all the parameters needed in the main constructor.

Parameters:: config_params – The yaml node with config params

~Setpoint(): Destroy the Setpoint object.

Setpoint(Setpoint&&) = default: Construct a new Setpoint object using the move constructor.

Setpoint &operator=(Setpoint&&) = default

Construct a new Setpoint object using the move assignment operator.

Returns:: Setpoint&

void set_yaw_ref(float ref)

Set the Yaw Setpoint value to a user defined offset.

Parameters:: ref – the reference value to set

inline float get_min_throttle() const

Get the Min Throttle.

Returns:: float