Circuit Description
Navigation SystemHow the Circuit Works
The navigation unit and the display panel control unit are the main components of the navigation system. These two components communicate with each other through the GA-Net II communication bus. The GA-Net II communication bus is also used by the display panel control unit to communicate with the audio unit. The navigation unit generates the screen graphics, and then passes them to the display panel control unit as Red, Green, and Blue (RGB) color signals, and a sync signal. The navigation unit also connects to the F-CAN multiplex network, where it communicates with the gauge control module and the ECM/PCM.
System Diagram
Power Supply
Fuse 7 (in the under-dash fuse/relay box) is hot at all times and supplies battery voltage to the navigation unit and to the display panel control unit.
With the ignition switch in ACC (I) or ON (II), battery voltage is applied through fuse 32 (in the under-dash fuse/relay box) to the navigation unit and to the display panel control unit.
User Controls
The navigation system can be controlled in three ways; (1) voice commands, (2) hard button inputs, and (3) touch screen inputs. The hard button and touch screen input information is communicated to the navigation unit from the display panel control unit via the GA-Net II communication bus. The voice commands are communicated to the navigation unit by the microphone in the roof console when the TALK switch on the steering wheel is pressed. The navigation unit compares the microphone signal with a library of stored voice files in order to find a match. Most of the navigation, audio, and HVAC functions can be controlled with voice commands. When the voice control system is in use, all of the speakers are muted. Refer to the Navigation System Owner's Manual for a list of valid voice commands.
Navigation Function
The navigation system utilizes the GPS signals obtained by the GPS antenna, the vehicle speed signal from the ECM/PCM, and the yaw rate sensor contained in the navigation unit to get a user from a starting position to a destination position. The position of the vehicle icon on the map is determined jointly by the GPS signals, the vehicle speed signal and the yaw rate sensor. The navigation system relies on DVD maps and points of interest (POI) in order to provide the user with the optimum route between starting and destination positions.
Route Guidance
When en route to a destination, the navigation system provides turn-by-turn map and voice guidance. The audio system outputs the navigation voice guidance prompts to the front center speaker. During navigation voice guidance prompts, the normal audio signal to the front center speaker is muted.
F-CAN Communications
F-CAN multiplex network information is transmitted across the communication lines for "real time" functions such as vehicle speed, fuel, emissions, and traction control data. The ECM/PCM sends the vehicle speed signal to the navigation unit via the F-CAN multiplex network. The navigation unit uses the vehicle speed signal and the yaw rate sensor to keep track of the vehicle's direction and speed of travel.
GPS Signal Reception
The GPS signals obtained by the GPS antenna are provided by up to 24 different satellites. The navigation unit supplies the GPS antenna with 5 V through a coax cable to power the antenna's amplifier. The GPS receiver in the navigation unit receives the amplified GPS signals back through the same coax cable. The GPS receiver identifies the satellites and processes the different GPS signals. These signals are then converted to actual locations by the navigation unit in order to determine the position of the vehicle.
Note: Rear metallic window tinting or loose items sitting on the rear shelf can block GPS signal reception entirely.
HFL Integration
The navigation system is fully integrated within the HandsFreeLink (HFL) System. If a Bluetooth cell phone is "Paired" (introduced to the vehicle using the "pairing" procedure), then the phone can be utilized for calling by the navigation system. By touching the green "phone" icon to the "Calculate route to:" screen, the navigation control unit passes the phone number to the HFL. The navigation control unit also senses from the HFL whether a paired phone is present, and uses this data to "light up" or "dim" the phone icon on the same screen.