GPS component mistake?

[radist73]

Hi,
Just tryed GPS component to read Latitude and Longtitude, but seems as Latitude read fail and really it have read Altitude.
Longtitude read show 24, 774 (Tallinn, Estonia) it is OK result, But Latitude read is between 5,xxx and 6,xxx, but need to be a 59,430. Before any steps of update it works fine (~1 year ago).
ReadLatitude and ReadAltitude give the same result. Data in GPS receiver output is ok.
Could you check it?
My flowchart attached.
Master side every 15sec ask for GPS cootdinates of slave side by RF LoRa transceiver connected to UART1

Thanks!

[Benj]

Hello,

I can't see any problems in the component source. Are you using the latest (v7.3) and have you applied the fixes listed here.

viewtopic.php?f=63&t=19743

[radist73]

Hi,
Now I have made a simple program with PIC18F26K40, I2C LCD and GPS module for testing. It start working with Software i2c.
But position read is strange. Longtitude is stable 24,774xxx but Latitude hops between 59,096 and 60,430 (it is approx. 200km distance) Right value must be 59,429

[petesmart]

Hi,

Sounds like a GPS problem rather than a coding/component problem.

As a suggestion, check the number of satellites that your GPS device can see...I think you need at least 8 to get a solid reference for longitude. Sometimes the GPS device can not see a wide enough arc of the sky, I often use an external antenna when I’m developing in the lab...

From memory I think the component allows you to check no of satellites visible..

Edit...I also note in your post that you have a LORA transceiver operating simultaneously....I would turn off the LORA device and re test GPS stability to check your not getting any RF interference or GPS rx front end overload....even though both device might not be on the same frequencies, harmonics often fall within rx passband of the GPS rx..if this is the case then the GPS will definitely be unstable...

Once we prove this is the case or not, then we can look at RF design


See how you go..

Best

Pete

[radist73]

Hi,
Thanks for answer.
My last test program have only GPS and LCD, file attached, and have same problem.
I have tested GPS with LCD about year ago, when just purchased FC7, it works fine. GPS receiver send out position data only if it receive signals from needed number of satellites, I have tested it in different places and outside.

Edit: will test other type of GPS receiver, may be problem in chineese GPS device (2pcs tested, result is same)
I have this model https://m.banggood.com/GPS-Module-with- ... 00984.html

[radist73]

Just checked it again, GPS receiver connected to PIC and receiver output connected to Terminal. In terminal window GPS signal have stable fixed values, but LCD show fixed Longtitude value and unstable 59,xxx-60,xxx latitude value...

[kersing]

It might help for debugging if you provide output from the GPS as seen in the terminal.

[Benj]

Hello,

Can you output the number of satellites.

Could it be that when connected to the PC you are getting many more satellites then you are when connected to PIC?

Are you running the GPS module inside or outside?