GPS evaluation board and GPS receiver

[powerman]

There's a few things i would like to ask about this two components.
1. Power supply for GPS evaluation board.
I understand that the power supply for the evaluation board can only be tranmitted from USB and the barrel Jack. However, if im using the Rs232 interface instead of USB to integrate with my microcontroller, how much voltage should i provide to the barrel jack?

2. Switch on the GPS evaluation board.
There are two switches, one is the RS232/USB switch which i know. But what does INT/EXT precisely do?

3. Software Mini GPS
The mini GPS has no readings when i use the USB. and i didnt get to try in RS232 as the power supply has not been made for the board. Is there a driver to be installed? where can i get the driver to install on to my PC to check if its working?

[waiweng83]

1. Power supply for GPS evaluation board.
I understand that the power supply for the evaluation board can only be tranmitted from USB and the barrel Jack. However, if im using the Rs232 interface instead of USB to integrate with my microcontroller, how much voltage should i provide to the barrel jack?

7 - 15V.

2. Switch on the GPS evaluation board.
There are two switches, one is the RS232/USB switch which i know. But what does INT/EXT precisely do?

According to the schematic, when "internal" is selected, the output from the GPS will be connected to the MAX232 circuit and USB circuit onboard.

If "external" is selected, the out output from the GPS will be disconnected.

3. Software Mini GPS
The mini GPS has no readings when i use the USB. and i didnt get to try in RS232 as the power supply has not been made for the board. Is there a driver to be installed? where can i get the driver to install on to my PC to check if its working?

Please make sure the Baud Rate is correct, "USB" and "Internal" has been selected.

We're sorry that we didn't put the link for the USB driver. You can download it from here: http://www.cytron.com.my/attachment/USB%20Driver.zip

[powerman]

Hi moderator,

Thanks for your reply. however i still have further inquiries if you dont mind.
you said that :

According to the schematic, when "internal" is selected, the output from the GPS will be connected to the MAX232 circuit and USB circuit onboard.

If "external" is selected, the out output from the GPS will be disconnected.

does this mean that if external is selected nothing happens? basically i use internal for RS232 too?

And another question, this evaluation board is intergrated with the GPS module Cytron is selling at the site, and i got them both. If im not mistaken the GPS receiver uses NMEA packets to transfer data. May i know which packet gives the output of latitude and longitude?

quoting from your data sheet you have placed on the website, is it
Packet Type: 314 PMTK_API_SET_NMEA_OUTPUT?
0 NMEA_SEN_GLL, // GPGLL interval - Geographic Position - Latitude longitude?
So for example if latitude and longitude is (1000,2000) what would be the output packet from the GPS to the receiver ?

[Jiewy]

If u want just the lat and long, u should go for GPRMS.
Just set ur baudrate to the correct one, com port (go check in ur device area), set ur gps eval board to usb and internal, U should be able to see the nmea data.

But on how to parse the nmea, i am still working on it.

HEY ADMIN< HOW DO U CHANGE THE BAUDRATE OF THE EB85A, can u pls pls pls tell me!

[waiweng83]

does this mean that if external is selected nothing happens? basically i use internal for RS232 too?

Yup, that's right.

And another question, this evaluation board is intergrated with the GPS module Cytron is selling at the site, and i got them both. If im not mistaken the GPS receiver uses NMEA packets to transfer data. May i know which packet gives the output of latitude and longitude?

As Jiewy mentioned, the GPS will output the NMEA by default. Just look for the string start with "GPRMC" as below:

$GPRMC,021154.800,A,0523.5321,N,10024.5120,E,0.21,0.00,100510,,,A*63

For the meaning of each field. A quick search on google will give you a lot of links.

HEY ADMIN< HOW DO U CHANGE THE BAUDRATE OF THE EB85A, can u pls pls pls tell me!

We normally change the baud rate by using the miniGPS software. But please take note that you need a backup battery to maintain the setting in the GPS module. Else, the baud rate will be reset to the factory default value when it's power cycled.

Alternatively, you may change the baud rate by issuing a "PMTK_SET_NMEA_BAUDRATE" command to the GPS module. However, we never tried this method before.

[Jiewy]

Haiz, that would mean that i cant set the GPS baudrate using MINIgps coz it will reset to 38400 once i turn it on and off? zz

Okie u mentioned something about the PMTK_set_baudrate but how do i send this to set the baudrate? Hyperterminal--> how? I am in a real pinch right now...

[Jiewy]

There is something i wanna clarify. It seems that i can change the configuration through MINIGps But i cant seem to find the " Write setting into flash " in the tab 'test' in the MiniGps.

Is it the program or my Gps module problem?

[powerman]

Hi Moderator,

Thanks for your quick reply again. However i have another problem. This is my scenario:
1. Im using the USB port just to supply power
2. Im using the RS232 port to interact with a micro controller with a serial port
3. The LED indicating the TX and RX for the serial port at the micro controller is not flashing, indicating that no data is transferred. I've tried it with another device and the program works fine.
4. Im doing my programming inside the university (indoors)

Can you help me with this problem? It seems to me that the GPS module is not transmitting any data through the rs232 port to my micro controller. Is it due to scenario number 4? when the GPS receiver is not able to obtain any satalite, will there still be any readings?

[waiweng83]

You need to make sure "RS232" is selected at the Interface Select switch. Another thing is you need a MAX-232 circuit to interface with your MCU.

If you are testing the GPS unit indoor, you will still get the data from the GPS unit. But the data is invalid and it will indicate that the GPS is not fixed.

[powerman]

Hi Moderator,

Ok my GPS unit is working. MAX circuit has already been implemented in the system. However, when i set printf("%c",(RXDATA)), weird numbers and charactors appear. Any idea how to resolve this problem?