Is there any known traps or limitations when running a L80 GNSS at “high” speed: 57600 bds / 10hz
I use
$PMTK251 SET_NMEA_BAUDRATE for 57600bds
$PMTK314,0,1,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,028 for the selection of CGA and RMC frame
$PQTXT,W,0,022 for desabling PQTXT frame
$PMTK220,100*2F to set the the POS_FIX at 10hz
All seems OK, and I can read the acknowledges of the previous commands and I receive the frames.
In my application I read the decoded values with the helps of a specific library (tinyGPS++) and it seems that now and then time the latitude and/or the longitude or the elevation are set to 0.0.
Any idea ?
Thanks
Hi，
L80 supports serial port 57600 baud rate and 10Hz update rate, this function is no problem.
Please confirm whether the NMEA sentence output by the module before decoding is normal? If possible, please provide data log.
In addition, please provide L80 version information, you can query through the following command: $PQVERNO,R*3F
Best Regards
Hi,
Thank you for your help.
The answer to $ PQVERNO is: $ PQVERNO, R, L80GR01A07S * 56
During my test, I do not have easy access to NMEA sentences and the error does not happen often.
I will do further testing and keep you informed if I can get any interesting results.
I will try to trap all the raw characters coming from the L80 in a ring buffer before they are used by my application and save / dump it when a problem is detected. Perhaps I will know the last sentences processed at the time.
Best regards
Okay, please feel free to communicate if you have any questions.
Best Regards
Hi,
I think I discovered the origin of the problem: it seems to be the serial link between my processor (an ESP8266 wifi bug) and the L80. I run the link at 57600bds and it seems that bits are wrongly transmitted and decoded. It happens only a few times in a long test sequence but the results are a “bit” annoying for my application.
When a problem was found by my test program, the last sentence sent to NMEA parser was:
$GPRMC,042504.900,A,401".1002,N,00440.4650,E,0.00,334.28<110321,A6D
It is obviously bad: there is a " in the middle of the latitude and a < at the end in front of the date field. The checksum is good.
The right sentence is:
$GPRMC,042504.900,A,4012.1002,N,00440.4650,E,0.00,334.28,110321,A6D
Only 2 bits changed: the " code x22 should be 2 code x32, and the < code x3c should be a , code x2c .
Both sentences have the same good checksum.
I found other similar cases with mangled sentences and good checksum that give 0 for latitude/longitude with the parser that I use.
So the problem seems to be with the serial link and the NMEA parser.
Best regards
Francis
PS: I changed a bit the real value of the coordinate. I don’t stay in the middle of Mediterranean see 
Hi，
So the problem seems to be with the serial link and the NMEA parser.
——
Yes，I think most likely so.
PS：If possible, please provide the serial link circuit diagram.
Best Regards
The link is with a softwareSerial emulation on pins 0 and 2 of the ESP8266, with rather short wires. No specific hardware.
pin 0 is input pin of the ESP/ output of the L80, and pin 2 is output for the ESP/input of L80.
I relaly think that the problem is not with the L80