Exploring Param Control

Parameters may be sent through MAVLink following Parameter Protocol.

Initially, parameters may be read in using:

master.mav.param_request_list_send(master.target_system, master.target_component)

The PARAM_VALUE message will be returned holding characteristics about all params

• param_id: name of the parameter stored on the device
• param_value: value of the parameter
• param_type: type of the value stored for the parameter (defined by MAV_PARAM_TYPE
• param_count: Total number of parameters
• param_index: Index of current parameters out of all parameters

Following the Parameter Protocol, a parameter may be sent using the "param_set_send" function:

def param_set_send(self, target_system, target_component, param_id, param_value, param_type):
    '''
    Set a parameter value TEMPORARILY to RAM. It will be reset to default
    on system reboot. Send the ACTION
    MAV_ACTION_STORAGE_WRITE to PERMANENTLY write the RAM
    contents to EEPROM. IMPORTANT: The receiving component
    should acknowledge the new parameter value by sending
    a param_value message to all communication partners.
    This will also ensure that multiple GCS all have an
    up-to-date list of all parameters. If the sending GCS
    did not receive a PARAM_VALUE message within its
    timeout time, it should re-send the PARAM_SET message.

    target_system             : System ID (uint8_t)
    target_component          : Component ID (uint8_t)
    param_id                  : Onboard parameter id (char)
    param_value               : Onboard parameter value (float)
    param_type                : Onboard parameter type: see MAV_VAR enum (uint8_t)
    '''
    return self.send(self.param_set_encode(target_system, target_component, param_id, param_value, param_type))

When a param is sent, the PARAM_VALUE message will be returned with the changes made to the variable. To store this param directly to ROM, the ACTION MAV_ACTION_STORAGE_WRITE must be sent. This is done using:

master.mav.command_long_send(master.target_system, master.target_component,
                             mavutil.mavlink.MAV_CMD_PREFLIGHT_STORAGE, 0, 0, 0, 0, 0, 0, 0, 0)

PARAMS Used

• WPNAV_RADIUS: radius for position accuracy used for waypoints. Waypoint structure defines as mm, value passed in is cm. Result is /10.