L76 PQPREC giving incorrect response

gaz · December 8, 2019, 7:12am

I have an L76 GNSS module (purchased this year) that I configure with;
PMTK220,100
PMTK301,2
PMTK313,1
PMTK285,3,2
PMTK353,1,1,0,0,1
PMTK386,0.1
PQPREC,W,6,6,3,1
PMTK314,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,1,1

All commands except PQPREC and PMTK353 return success.
With PQPREC, the documentation says the module should return “PQPREC,W,OK” on success and “PQPREC,W,ERROR” on failure. Instead, the module echoes the command back and doesn’t change the precision of the output.

I’ve tried sending only PQPREC but the module still only echoes the command without changing precision.
Sending “PQPREC,R” also fails to report the current precision. The module similarly echoes the command back without including the current set precision.

What have I missed?

sammy-Q · December 9, 2019, 1:38am

Dear Gaz,

PMTK353 command, you could read the note in L76 GNSS protocol spec:
GLONASS and BeiDou can not be enabled at the same time. Galileo and BeiDou can not be enabled at the same time too
So PMTK353,1,1,0,0,1 is not supported.
For PQPREC,W,6,6,3,1, do you send $PQPREC,W,6,6,3,1*7C?
If yes, maybe your FW version doesn’t support this command.
Please send command
$PMTK605*31(response should be PMTK705)
and $PQVERNO,R*3F, keep all reponse for me.

gaz · December 9, 2019, 12:27pm

Hi Sammy,

I should have read the docs closer. Thank you.
Yes, I am sending $PQPREC,W,6,6,3,1*7C
PMTK605 returns $PMTK705,AXN_3.8_3333_16042100,0006,Quectel-L76,1.0*0B
PQVERNO,R returns $PQVERNO,R,L76NR02A07S,2016/04/22,12:44*6D

sammy-Q · December 10, 2019, 1:52am

I think maybe your FW version is old, please try to upgrade to the latest version L76NR03A03S.
FW and user guide download link:https://cnquectel-my.sharepoint.com/:f:/g/personal/europe-fae_quectel_com/EvpnwMdrXmVFuvjFQy6wZDMBaFRPUiO7Al30qIJeLUvtqw?e=Xe8Ho4
Flashtool:https://cnquectel-my.sharepoint.com/:u:/g/personal/europe-fae_quectel_com/EZ-Yz3dfMFhCiKkGAKJQ4IEBNbvxdu3YkuTDs4rJCGi6PA?e=o8wJee

gaz · December 10, 2019, 9:30am

That was it. Thank you Sammy. It’s all working now.

giulio.iselqui · September 25, 2023, 4:55pm

Hello @sammy-Q , Hello @Raphael-Q,

I am using an L76 module on a board that was assembled this year (so the module should have inside newer firmware than in 2019 since when this topic was open).

I did not manage to change the precisios to 5 digit for latitude and longitude.

I don’t get any responce if I send the command same as it is reported in the: Quectel_Lx0Lx6LC86LLG77L_GNSS_Protocol_Specification_V2.1.pdf

$PQPREC,W,5,5,2,1*7D

No responce either if i try to get the current setting with:

$PQPREC,R*7B

Any suggestion on how to use this command?

Thanks and best regards.

Giulio

Raphael-Q · September 27, 2023, 11:32am

Hi Giulio,

L76 supports $PQPREC to adjust decimal since L76NR03A01S and this firmware is released in mid 2017.

Please confirm if you can send other commands to the module successfully. If the module doesn’t reply to any commands, please check whether the serial port is occupied.

Best regards.

giulio.iselqui · September 28, 2023, 3:39pm

Hello @Raphael-Q

looks like it’s a problem of firmware version.

$PMTK705,AXN_3.8_3333_16042100,0006,Quectel-L76,1.00B
$PQVERNO,R,L76NR02A07S,2016/04/22,12:44 6D

Could you please share the link for the flash tool, a manual and the bin file of the lastest firmware?

Thank you

Best regards

Giulio

Raphael-Q · October 7, 2023, 1:16am

Hi Giulio Iselqui,

I will send you latest firmware via message.

Best regards.

giulio.iselqui · October 13, 2023, 5:00pm

Hello @Raphael-Q,

Thank you for the support with firmware update.
I updated L76 module with success to the lastest firmware version.

But even managing to change the coordinates format from 4 to 5 digits we are experiencing something strange.

This is the scenario.

We place the antenna board mounting the L76 module in a fixed location on the roof of a tall building (no obstacles above the antenna and full sky visibility) together with an antenna mounting the module from another vendor for comparison. Then we log the coordinates for 2 minutes and we compare the results.

In 2 minutes the coordinates gathered from L76 module are stuck to fixed values, no either the last fifth digit is changing in latitude or longitude. The same is not happening for the other module showing a little change during time in cooardinates value (and this is what we would expected considering an avarage precision of the 2.5m)

It’s like if L76 is working in a filtered configuration. Could this behavior related to the “Navigation mode” or if there is any other setting we could change to make the behaviour to match the module from the other vendor.

Thank you

Giulio

Raphael-Q · October 20, 2023, 2:25pm

Hi Giulio,

Your test environment is very good with clear sky. In this senario, the module performance should be stable. It is reasonable that L76 have location unchanged.

Besides, L76 have speed threshold for static navigation. Which means that if the speed is lower than threshold, L76 will limit the drifting. You can change the speed threshold to 0, but it will cause inaccuracy in some weak signal senario.

By the way, does this problem only ouccur after changing digits to 5 in the same open sky environment?

Best regards.