Hello, this is my first topic in this forum. I have some questions below:
1-) It is mentioned sending reference time and position on every startup after uploaded EPO file to L86 module on " Quectel_Lx0Lx6LC86LLG77L_AGNSS_Application_Note_V1.2-1 ". We have voltage on V_BCKP pin without interruption. Because of this, our module will not forget time and last known position i think. So do we still need to send reference time and position on every startup?
2-) Should we disable EASY to AGPS with EPO be effective?
3-) Is there a way to stop gps information( auto messages on every second for lon, lat, alt, speed etc. ) in binary mode to communicate with module properly for sending epo, confirming epo and to switch to NMEA mode?
4-) Do you recommend updating module’s firmware? What are the benefits of updating the module’s firmware? How can we reach release notes about firmware versions?
5-) I read about updating L86 firmware can help module to get data from Galileo Satellites also in this forum. Do we need to change baud rate to 19200 or higher after update firmware to get Galileo Satellites like LC86L?
Thanks for replies in advance. Best regards.
Hi Sacredserenity,
1-) It is recommended to send reference time and position while startup. In case of EPO is invalid, time and position will help improve TTFF performance.
2-) There is no need to disable EASY, EASY and AGNSS won’t affect each other.
3-) After sending EPO data to L86, the module will automatically process the data.
4-) Updating firmware is always welcome. The latest firmware will fix some bugs and improve stability. The release note will be sent along with the firmware package.
Query firmware version via $PQVERNO,R*3F
The latest version is L86NR03A01S
5-) If you need a higher fix rate(> 1 Hz) or a large data streams need to be transferred, you may a higher baud rate. Another scene is that the command you sent can not get a response( PMTK_ACK message) immediately, that means the port is stuck and you need to improve baud rate.
( from GNSS_Protocol_Specification)
Best regards.
Thanks for your detailed answers Raphael,
According to " Quectel_Lx0Lx6LC86LLG77L_AGNSS_Application_Note_V1.2-1 " page 26,
- Send Reference Time to GNSS module with $PMTK740.
- Send Reference Position to GNSS module with $PMTK741 or $PMTK713.
Is it ok to just send time and reference position together with $PMTK741 without send time with $PMTK740 first?
How we can get latest firmware and is there a program to upload firmware to module?
Best regards.
Hi Sacredserenity,
1-) Yes, it is ok. Actually, EPO data helps the most improving TTFF.
2-) The latest firmware and flash tool are sent via message.
Best regards.
Hello Raphael,
According to " Quectel_Lx0Lx6LC86LLG77L_AGNSS_Application_Note_V1.2-1 " page 26,
After upload EPO file to module we should restart GNSS. Is it ok to cut power of VCC while we keep power of V_BCKP for restart GNSS. If it is not, how can we restart GNSS?
Basically our procedure like this:
After upload EPO file we cut power of VCC while we keeping power of V_BCKP. After 1-3 hours( V_BCKP still has power without interruption ). We give power to VCC, and we send current utc time and approx. position to module via uart.
Is this procedure correct?
Thank you again and best regards.
Hi Sacredserenity,
To perform a reset, you can send a hot start command( $PMTK101*32 ). Hot start clears no data.
If you want to clear up expired EPO as long as reset module, you can send a cold start command( $PMTK103*30 ). Cold start clears time, position, almanacs and ephemeris data.
After uploading EPO, cutting off VCC and holding VBCKP performs a warm start, position data may be cleared up.
But please remember that EPO data is valid within 2 hours. If VCC is dowm over 2 hours, please download the latest EPO from server. Inject EPO, time and position to module to finish AGNSS.
If the module is powered up again within 2 hours, there is no need to download a new EPO.
Best regards.
Hello Raphael,
" After uploading EPO, cutting off VCC and holding VBCKP performs a warm start, position data may be cleared up. "
1- Does it clear up EPO data or last known position data? Does warm start also reset GNSS?
“But please remember that EPO data is valid within 2 hours. If VCC is dowm over 2 hours, please download the latest EPO from server. Inject EPO, time and position to module to finish AGNSS.”
2- We are sending 3 days EPO file. Does even 3 days EPO file still valid up to 2 hours while VCC powered down and V_BCKP powered up? Is it exactly 2 hours or do we have some margin like 2 hours+5 minutes?
3- Procedure1: Basically after uploading EPO file we shouldn’t cut off VCC, instead we should send hot start command. After sending hot start command we can cut off VCC to module go low power mode while we keeping V_BKCP. And then after within 2 hours we should power on VCC again and send time and position. With this procedure AGNSS will be finished. Have I got that right? 
4- Procedure2:Or after uploading EPO file we can cut off VCC while keeping V_BCKP without hot start command. After that, within 2 hours we do power up VCC and send reference time and position and AGNSS will be finished.
Are both procedures correct?
Best regards.
Hello Raphael,
I think i have one more question.
“If the module is powered up again within 2 hours, there is no need to download a new EPO.”
Is 2 hours limit time related with power issues( because of some memory needs power to hold data) or some data expiring issues( because changes of satellites position etc. )? If its because of power issues, in every 2 hours we can power on VCC til first sentences( MTKGPS sentences ), after first sentences we can power off VCC pin again to extend EPO file life. With this approach VCC pin will has power for approx. 0.2-0.5 sec in every 2 hours period. Would this approach be correct?
I know i asked very detailed questions. Thank you for your patience.
Best regards.
Hi Sacredserenity,
About the 2-hours limited time, I confused with another platform. A 3-days EPO is valid within 3 days.
Warm start and cold start command are to simulate real usage conditions, like power off VCC but hold VBCKP, and completely power off the module. See Protocol Specification. You can also use the two commands to clear up expired EPO data and then upload the latest EPO to the module.
Procedure2 :Or after uploading EPO file we can cut off VCC while keeping V_BCKP without hot start command. After that, within 2 hours we do power up VCC and send reference time and position and AGNSS will be finished. Procedure2 is generally correct
Before uploading new EPO data. It is recommended to send $PMTK127*36 first to clear up expired EPO data. That aims to ensure a sufficient space for new data.
in every 2 hours we can power on VCC til first sentences( MTKGPS sentences ), after first sentences we can power off VCC pin again to extend EPO file life. With this approach VCC pin will has power for approx. 0.2-0.5 sec in every 2 hours period.
That is a good approach while VCC power off for a long time. But I have to remind you, the longer time VCC power off, the less accurate when first wake up. Because EPO data is a prediction of satellites, the error will accumulate. Don’t worry, it still helps location a lot except that the module is moved a long distance while powered off.
At last, never mind for asking me more.
Best regards.
