| Q. |
How do I monitor the output data or send commands? |
| A. |
The module will output serial data at 9600 baud at 3v logic levels via 2 serial ports. This requires a RS232 level converter to connect to a PC comport. Once the data is connected to the PC comport, the supplied software VisualGPS or SiRFDemo can be used to view the data content and send commands. |
| Q. |
How do I know if the module is operating correctly? |
| A. |
A GPS fix will indicate that the unit has a reasonable signal, and is working. Using the VisualGPS PC software and a Comport serial adapter, the signal levels of each satellite can be measured. A good design will give C/No levels of satellites with high elevations of up to 50dBHz. |
| Q. |
The unit receives good signal levels, but does not get a position fix? |
| A. |
If the GPS receiver is still in acquisition mode this can be expected. However, a prolonged lack of position fix could be caused by too much electrical noise in the application. Moving the antenna away from noise sources may allow improvements. More filtering on the receiver power supply or increasing the size of the design ground plane also may be of benefit. It is not recommended to have high speed digital switching close to the sensitive RF input section of the GPS receiver. |
| Q. |
Does the module provide power to an active? |
| A. |
A DC supply can be applied to a dedicated input pin (VANT) on the receiver. If a passive antenna with an inherent DC short is used, this DC supply must not be connected |
| Q. |
What type of antenna should I use? |
| A. |
Most applications call for an active antenna (with built in amplifier). A passive antenna may be used if the cable length is very short. |
| Q. |
I don't have a backup-battery, how will performance be affected? |
| A. |
Battery backup improves the Time To First Fix. Without this, the unit will still function normally, but will always start in a cold start mode. |
| Q. |
I do not have a battery backup. What information will I lose when the power goes off? |
| A. |
The next time the unit is turned ON it will use the cold start conditions to get a satellite fix. The time and last known ephemeris will be lost, and the serial I/O parameters will return to the default settings. |
| Q. |
What level of gain is required for an external active antenna? |
| A. |
An appropriate antenna system will provide +15 to 30dBi (includes antenna gain, LNA gain and cable loss). More details are available in an application note. |
| Q. |
Does the module support firmware updates? |
| A. |
Yes, new firmware can be loaded using a serial port and the "boot"” input. It is essential to provide test points on the application board to allow connections to the "serial port” and "boot” input. |
| Q. |
What size passive antenna is recommended? |
| A. |
We recommend physical dimensions not less than 25mm square. Smaller antennas have reduced ability to receive GPS signals. Passive antenna gain of +3dBi should be sufficient |
| Q. |
For DR applications, what gyro does NAVMAN recommend? |
| A. |
NAVMAN recommends the Panasonic EWTS82 gyro. |
| Q. |
Why does the unit not output any data? |
| A. |
- Visually inspect all connections
- Check the supply current, it should be approx 75mA
- Check the voltage on VDD pad 1 (2.9 to 3.6vDC)
- Check the reset input level on pad 22 (3vDC)
- Check the presence of data on pad 5 |
| Q. |
Why does the unit not get a GPS fix? |
| A. |
- Check the antenna connection, use the DC supply in the antenna cable to test for a good connection.
- Using the GPS analyser PC software and Comport serial interface, check the signal levels, which should be above 38dBHz for good navigation. |