GPS project

Projects General Guidance
1

Hi all,

I am a complete Newb with the Arduino but am familiar enough with general electronics, GPS and other hardware. I want to build a simple GPS clock which will export both an NMEA ZDA time message and a 1PPS TTL signal to an external piece of hardware. I need to export the NMEA message via RS232 serial so will need a DB9 connector. I also need the 1PPS routed to pin 9 of the DB9 AND coupled to a BNC connector.
I would also like a simple LCD display showing GPS time and an LED to indicate the 1PPS pulse presence.

I can see that there are several arduino boards available but i am not really sure where to start!

Could one of you knowledgeable guys point me in the right direction here?

Thanks very much

2

201siggy:
Could one of you knowledgeable guys point me in the right direction here?

You have described what you want your end-product to do but you have not said what exactly you need help with.

Have you got any of the hardware?

Have you written any programs to interface with the hardware?

...R

3

Hi Robin,

I have the receiving hardware ( which is a PC with software listening to a COM port) so I guess my first question is related to which Arduino board and accessories would work for my application. Once I have identified the board and the GPS module I can start looking at the software.

Thanks

4

There are lots of Arduino/GPS starter projects on line. You might even find one that has an LCD GPS time display. Do some research see what others have done and written up.

You won't find any that do everything you want. So, buy any Arduino board and start learning about the Arduino programming environment.

5

The GPS module by itself, does what you describe. You don't need any Arduino, unless you really need to filter the NMEA messages. If so, I'd like to know why the PC can't do that.

6

aarg:
The GPS module by itself, does what you describe. You don't need any Arduino, unless you need to filter the NMEA messages.

I am only interested in the ZDA (time) message
Which GPS module do you mean?

Thanks

7

Most any GPS module will "export the NMEA message via RS232 serial" and I think all have some sort of 1PPS output.

If you mean the ancient standard +/- 12V RS232 serial, you will need a serial adapter module, not an Arduino. The Arduino is of interest only for manipulating the NMEA data.

8

The application is hydrographic survey and I have a highly accurate dual RTK receiver giving me position & attitude. What I need is to synchronise the PC clock with GPS time. The software running on the PC has a routine to read ZDA on a COM port, along with a 1PPS on COM port pin 9 to discipline the PC clock which is then used for system timing.

So I need some sort of device to lock on to a GPS signal and export a simple 1PPS and ZDA on a COM port. A display is a nicety but desirable.

I could of course just buy a GPS with a 1PPS output but I wanted to take the opportunity to learn a little about Arduino or RPi in the process.

9

I don't see how either an Arduino or an RPi will be useful for your latest project description.

So I need some sort of device to lock on to a GPS signal and export a simple 1PPS and ZDA on a COM port

That would be just about any GPS module, combined with an RS232 serial com port adapter.

10

You could use the Arduino to monitor the data and PPS pulse. I would recommend a bridging configuration where the Arduino only senses the traffic, not passing through as that would introduce delays.

11

I realise that a GPS module like a BU-353 would give me the ZDA and 1PPS. However, I would like to monitor the traffic using a display of some sort plus an indicator for the 1PPS. Also, these GPS modules are typically USB interface not serial. Yes, I could use a USB to serial adapter but as I mentioned, I would like to learn a bit as I go along.

Thanks

12

You can't use a GPS module with a USB interface with an Arduino. You can only use the serial interfaced ones.

13

201siggy:
I am only interested in the ZDA (time) message

Does that sentence always, and only, put out UTC ?

At GPS startup the time a GPS publishes in the NMEA sentences can be different from UTC by some seconds.

Does the ZDA sentence deliberatly block publising the time until the GPS has received the leap seconds update ?

14

the thing about most Arduinos: the hardware serial is on the same pins as the IO. my board of choice is the Mega, which has 4 ( 3 usable ) hardware serial ports