Crio 9014, collecting analog and GPS data

[sharda]

Hi,

I am using CRio 9014 and have a program up and running to collect data from 15 analog channels. I want to add GPS NMEA string GGA. I may use the GPS lat/lon and time to synchronise the data. Can some one help me with initial startup?

I will appreciate,

Ajay

[Andrew_E]

Hi Ajay,

 Do you have a particular device which you can communicate to that has a GPS on it or are you thinking about searching a particular address on a site like google earth to poll the information? I have found this forum that describes the latter method if you are interested.

Regards,

Andrew

Message Edited by Andrew_E on 06-30-2009 11:26 AM

[sharda]

Hi Andrew,

I will be using a standard Trimble GPS wired and configured to send GGA string.

I would appreciate more leads on this.

Thanks,

Ajay

[sharda]

Hi Andrew,

Just to give few more insight, I have a FPGA reading the analog data and sending to the host machine and there I am writing all the stuff. I need the GGA string from a GPS source to be in the same textfile having lat, lon and GPS time.

Please suggest,

Ajay

[MathBoda]

If you want to synchronise analog data with GPS, the best way is to use a digital module (9401) to make 1 or 2 RS232 to get the data from the GPS.

By using the PPS (on the digital module), you will be able to grab the analog data between 2 pulses then decode the GPS data ( time + position) on the RT

On the FPGA:

DMA FIFO1 will be for analog data

DMA FIFO2 will bbe for RS232 

-Make one or two RS232 ( ode avalaible on the ni.com)

-Make a loop which change a FLAG (or using occurence) each time you have a PPS.

-Enable IRQ each time PPS has been detected.

-Find a way to know exactly how many analog data you have acquired since last pulse

!!!: Find a way to wait for the PPS before starting to write Analog data in the DMA FIFO

on the RT  

Make a loop which wait for the IRQ

Read in the FIFO1 data > download only number of analog data you have per second

Read RS232 data form FIFO2 > decode  GPS data > decode the GPS time of previous PPS then of the analog data

You will have 1 seconde of analog data + GPS data of the same seconde

By this way, you don't really care of RT clock.

You will have a stable clock without drift a data with GPS timestamp

Mathieu

[FixedWire]

Hi Mathieu,

I'm putting a system in place, rather on a short and rushed time frame, to gather 6 analog channels of data that need to be sync'd to GPS & PPS signals. Hoping to use cRIO as it needs to be rugged & small.

Any suggestions to not repeat past mistakes you have learned from? Suggestions are appreciated!