LC760Z Setting Fix Rate

IoT Modules GNSS Module
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1

Hi

I’ve build a navigation device that integrates a LC760Z aside an ESP32.

I need to enable 5Hz fix rate, but I did not managed to do so.

This is the command I sent to set device to 5hz :

const uint8_t fixrate_5hz[] = {
0xF1, 0xD9, 0x06, 0x42, 0x14, 0x00, 0x00, 0x01,
0x35, 0x32, 0xC8, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x8C, 0xD5};
Serial2.write(fixrate_5hz, sizeof(fixrate_5hz));

Also tried

sendNMEAWithResponse("$PQTMCFGFIXRATE,W,200");
The sendNMEAWithResponse function computes and appends the checksum before sending the command.

Sending other PQTMCFG... frames works and I get a response from the device.

I’ve setup GGA / RMC frames to be sent each fix:

sendNMEAWithResponse("PQTMCFGMSGRATE,W,RMC,1");
sendNMEAWithResponse("PQTMCFGMSGRATE,W,VTG,1");
sendNMEAWithResponse("PQTMCFGMSGRATE,W,GGA,1");

However the fix rate seems to stay at 1hz: I get GGA frames every second but not more.

Also, from times to times, even outside with clear sky and great fix (more than 10 satellites), the device sends GGA frames only and no RMC frames ?

PS : according to the documentation, the device doesn’t seem to support PAIR setup frames, but I sometimes receive PAIR frames sent by the LC760Z ?

Thanks

2

Hi @Ludovic,

Can you share the firmware version of the module?

To set the module to 5Hz fix rate:

  1. Set the positioning frequency (fix rate) using below binary command string:

F1 D9 06 42 14 00 00 01 35 32 C8 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 8C D5

  1. Then adjust the baud rate to 230400 or 460800 using CFG-PRT (0x06 0x00).

  2. Save the configuration using below command string using CFG-CFG (0x06 0x09):

F1 D9 06 09 08 00 00 00 00 00 2F 00 00 00 46 B7

  1. Reboot the module to apply the saved parameters.

As for the NMEA messages, while your function call ‘sendNMEAWithResponse’ likely handles the $ prefix and the * calculation automatically, the raw NMEA string sent to the module must include them to be accepted. E.g:

//Set:
$PQTMCFGMSGRATE,W,<MsgName>,<Rate>[,<MsgVer>]*<Checksum><CR><LF>
//Get:
$PQTMCFGMSGRATE,R,<MsgName>[,<MsgVer>]*<Checksum><CR><LF>

Example commands:
$PQTMCFGMSGRATE,W,RMC,1*17
$PQTMCFGMSGRATE,W,VTG,1*0E
$PQTMCFGMSGRATE,W,GGA,1*0A