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sensors: gnss buffer usage optimalisation #657

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sensors: gnss buffer usage optimalisation #657

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10 changes: 4 additions & 6 deletions sensors/common/gps/receiver.c
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Original file line number Diff line number Diff line change
Expand Up @@ -176,18 +176,18 @@ int gps_updateEvt(nmea_t *message, sensor_event_t *evtGps, float posStdev, float
evtGps->gps.utc = message->msg.gga.utc * 1000000;

gettime(&evtGps->timestamp, NULL);
break;
return 1;

case nmea_gsa:
evtGps->gps.hdop = (unsigned int)(message->msg.gsa.hdop * 1e2);
evtGps->gps.vdop = (unsigned int)(message->msg.gsa.vdop * 1e2);

evtGps->gps.eph = evtGps->gps.hdop * posStdev;
evtGps->gps.epv = evtGps->gps.vdop * posStdev;
break;
return 0;

case nmea_rmc:
break;
return 0;

case nmea_vtg:
evtGps->gps.heading = message->msg.vtg.track * DEG2MILIRAD; /* degrees -> milliradians */
Expand All @@ -197,13 +197,11 @@ int gps_updateEvt(nmea_t *message, sensor_event_t *evtGps, float posStdev, float

/* This is not 100% correct error estimation but the only we have */
evtGps->gps.evel = evtGps->gps.hdop * velStdev;
break;
return 0;

default:
return 0;
}

return 1;
}


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4 changes: 3 additions & 1 deletion sensors/gps/ubx.c
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Expand Up @@ -40,7 +40,7 @@
#define UBX_VEL_ACCURACY 0.0849f

#define REC_BUF_SZ 1024
#define INBOX_SIZE 3
#define INBOX_SIZE 8

#ifndef UBX_DEFAULT_BAUDRATE
#define UBX_DEFAULT_BAUDRATE B9600
Expand Down Expand Up @@ -215,6 +215,8 @@ static int ubx_alloc(sensor_info_t *info, const char *args)
write(ctx->filedes, UBX_PREMADE_FIX_10HZ, sizeof(UBX_PREMADE_FIX_10HZ));
usleep(100 * 1000);

write(ctx->filedes, UBX_PREMADE_UART1_OUT_NMEA_ONLY_115200, sizeof(UBX_PREMADE_UART1_OUT_NMEA_ONLY_115200));

@gemini-code-assist gemini-code-assist Bot Apr 28, 2026

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medium

Using sizeof() on a string literal includes the implicit null terminator (\0). Since UBX is a binary protocol, sending an extra 0x00 byte after the message is incorrect and may be misinterpreted by the receiver. It is recommended to use sizeof(...) - 1 to send only the actual message bytes.

write(ctx->filedes, UBX_PREMADE_UART1_OUT_NMEA_ONLY_115200, sizeof(UBX_PREMADE_UART1_OUT_NMEA_ONLY_115200) - 1);


info->ctx = ctx;

return EOK;
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3 changes: 3 additions & 0 deletions sensors/gps/ubx.h
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Expand Up @@ -35,4 +35,7 @@
/* Premade command that sets baudrate to 115200 */
#define UBX_PREMADE_BAUD_115200 "\xb5\x62\x06\x00\x14\x00\x01\x00\x00\x00\xd0\x08\x00\x00\x00\xc2\x01\x00\x07\x00\x07\x00\x00\x00\x00\x00\xc4\x96\xb5\x62\x06\x00\x01"

/* UART1, 115200, 8N1, input: UBX/NMEA/RTCM, output: NMEA only */
#define UBX_PREMADE_UART1_OUT_NMEA_ONLY_115200 "\xb5\x62\x06\x00\x14\x00\x01\x00\x00\x00\xd0\x08\x00\x00\x00\xc2\x01\x00\x07\x00\x02\x00\x00\x00\x00\x00\xbf\x78"

#endif
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