VehicleIO Workflow

Note

SW Release Applicability: This tutorial is applicable to modules in both NVIDIA DriveWorks and NVIDIA DRIVE Software releases.

Initialization

The dwVehicleIO_initialize() function creates a VehicleIO instance. That functions takes the following parameters:

• VehicleIO handle: dwVehicleIOHandle_t
• Type of interface device: dwVehicleIOType (DW_VEHICLEIO_DATASPEED / DW_VEHICLEIO_GENERIC / DW_VEHICLEIO_SPACEDRIVE / DW_VEHICLEIO_CUSTOM)
• Handle to the vehicle: dwVehicle

Note

Before creating a VehicleIO instance, you must initialize the rig configuration module using dwRig_initializeFromFile() and then get the vehicle properties using dwRig_getVehicle(). For more information, see Rig Configuration in this guide.

• Context Handle : dwContextHandle_t

Driving Mode

The dwVehicleIO_setDrivingMode() function sets the driving mode. This function consumes the dwVehicleIODrivingMode() enum as an argument, which is defined as

typedef enum dwVehicleIODrivingMode
{
    DW_VEHICLEIO_DRIVING_LIMITED = 0x000,
    DW_VEHICLEIO_DRIVING_LIMITED_ND = 0x100,
    DW_VEHICLEIO_DRIVING_COLLISION_AVOIDANCE = 0x200,
    DW_VEHICLEIO_DRIVING_NO_SAFETY = 0x300
} dwVehicleIODrivingMode; 

Vehicle State Information

The dwVehicleIO_consumeCANFrame() function parses received CAN messages. The resulting parsed messages generate certain reports, which can be gathered using the predefined callbacks.

The current vehicle state information can be retrieved with dwVehicleIO_getVehicleState(), which returns the vehicle state in the dwVehicleIOState format.

Sending Vehicle Commands

The dwVehicleIO_sendVehicleCommand() function sends a command to the vehicle via VehicleIO. The command is sent in the dwVehicleIOCommand format and is passed as one of the arguments. An additional argument is passed as a handle to the underlying sensor that VehicleIO uses to pass this command.

Selecting Driver Overrides

Signals that the driver uses to override Vehicle control are configurable and can be selected using dwVehicleIO_selectDriverOverrides(). The driver can override vehicle control with any combination of throttle, steering, brake, and/or gear.

Conditions for Engagement and Disengagement

In order to enable vehicle actuation (i.e. engage), several conditions must be satisfied:

• dwVehicleIOCommand::enable must be set to true.
• Desired dwVehicleIOCommand::*Valid flags must be set to true, for example dwVehicleIOCommand::brakeValid to actuate vehicle braking.
• All bits in dwVehicleIOState::faults must be clear. Recoverable faults can be cleared by sending a command with dwVehicleIOCommand::clearFaults set to true.
• dwVehicleIOState::overrides must be clear for all enabled driver overrides. To clear dwVehicleIOState::overrides, one has to send a command with dwVehicleIOCommand::clearFaults set to true (same field is used to clear faults and overrides).

Once engaged, both Drive-By-Wire hardware and/or VehicleIO might decide to disable vehicle actuation (i.e. disengage), there are a few cases when this might happen:

• Application-requested disengagement: dwVehicleIOCommand::enable is set to false.
• Disengagement due to Drive-By-Wire faults. Which hardware actuation unit caused the disengagement will be indicated via dwVehicleIOState::faults (see corresponding dwVehicleIOFaults enumeration). Exact reason for disengagement can be traced back using CAN logs and Drive-By-Wire vendor documentation.
• Disengagement due to driver overrides as detected by Drive-By-Wire hardware. Exact reason will be indicated via corresponding bits in dwVehicleIOState::overrides (see corresponding dwVehicleIOOverrides enumeration).
• If VehicleIO is in DW_VEHICLEIO_DRIVING_LIMITED mode, some commands (such as braking) that are considered not appropriate for limited actuation will cause VehicleIO to stop sending commands to the vehicle (i.e. VehicleIO will disengage). In this case, DW_VEHICLEIO_FAULT_SAFETY bit will set in dwVehicleIOState::faults.
• If VehicleIO stopped receiving Drive-By-Wire reports for more than 100 milliseconds and VehicleIO is in DW_VEHICLEIO_DRIVING_LIMITED mode, then DW_VEHICLEIO_FAULT_SAFETY bit will set in dwVehicleIOState::faults and VehicleIO will disengage.

VehicleIO Sample

See VehicleIO Sample