GNSS Protocol Reference

The Wireless Tracker uses the Unicore UC6580 GNSS module, which communicates via the Unicore protocol (compatible with NMEA-0183). This page covers the most commonly used commands.

Note

For the complete protocol specification, download the UFirebird Protocol Specification PDF.

Serial Configuration

Parameter	Value
Default Baud	115200
Data Bits	8
Parity	None
Stop Bits	1
GPIO TX	33 (GNSS → ESP32)
GPIO RX	34 (ESP32 → GNSS)

Message Format

All messages follow this format:

$MSGNAME,data1,data2,data3,...[*CC]\r\n

• $ - Message start
• MSGNAME - Command name
• , - Parameter separator
• *CC - Optional checksum (XOR of all characters between $ and *)
• \r\n - Message terminator

Common Commands

PDTINFO - Product Information

Query device information:

$PDTINFO

Response:

$PDTINFO,UC6580,G1B1,V4.1,R3.4.0.19,080101000001,000101114303845

Field	Description
pdtName	Product name
config	Configuration
hwVer	Hardware version
fwVer	Firmware version
PN	Product number
SN	Serial number

RESET - Receiver Reset

$RESET,type,clrMask

clrMask	Start Type
h00	Hot start
h01	Warm start
h85	Cold start

Example (cold start):

$RESET,0,h85

CFGPRT - Port Configuration

Query current port:

$CFGPRT

Set port configuration:

$CFGPRT,portID,addr,baud,inProto,outProto

Parameter	Description
portID	1 = UART1, 2 = UART2
addr	Always h0
baud	9600, 115200, 230400, 460800
inProto	Input protocol mask
outProto	Output protocol mask

CFGMSG - Message Output Configuration

Enable/disable specific messages:

$CFGMSG,msgClass,msgID,switch

Message	Class	ID	Switch
GGA	0	0	0=off, 1=on
GLL	0	1	0=off, 1=on
GSA	0	2	0=off, 1=on
GSV	0	3	0=off, 1=on
RMC	0	4	0=off, 1=on
VTG	0	5	0=off, 1=on
ZDA	0	6	0=off, 1=on
GST	0	7	0=off, 1=on

Example (enable GGA):

$CFGMSG,0,0,1

CFGSYS - Satellite System Configuration

$CFGSYS,sysMask

sysMask	Systems
H01	GPS+SBAS+QZSS
H10	BDS only
H11	GPS+BDS+Galileo+SBAS+QZSS
H101	GPS+GLONASS+Galileo+SBAS+QZSS

CFGSAVE - Save Configuration

Save current settings to flash:

$CFGSAVE

Caution

Do NOT power off within 1 second of sending $CFGSAVE. This can corrupt the configuration.

NMEA Output Messages

GGA - Position Fix

$GPGGA,time,lat,N,lon,E,quality,numSV,HDOP,alt,M,sep,M,diffAge,diffStation*cs

Field	Description
time	UTC time (hhmmss.ss)
lat	Latitude (ddmm.mmmmm)
N/S	North/South indicator
lon	Longitude (dddmm.mmmmm)
E/W	East/West indicator
quality	0=invalid, 1=GPS, 2=DGPS
numSV	Number of satellites
HDOP	Horizontal dilution
alt	Altitude (meters)

RMC - Recommended Minimum

$GPRMC,time,status,lat,N,lon,E,speed,course,date,magVar,magE,mode*cs

Field	Description
time	UTC time
status	A=valid, V=invalid
speed	Speed over ground (knots)
course	Course over ground (degrees)
date	UTC date (ddmmyy)

GSV - Satellites in View

$GPGSV,numMsg,msgNum,numSV,prn1,elv1,az1,snr1,...*cs

Reports visible satellites with:

• PRN number
• Elevation angle (0-90°)
• Azimuth (0-359°)
• Signal-to-noise ratio (dB-Hz)

ESP32 Code Examples

Basic Setup

#include <HardwareSerial.h>

HardwareSerial GNSS(1);

void setup() {
    Serial.begin(115200);

    // Enable GNSS power (V1.1)
    pinMode(3, OUTPUT);
    digitalWrite(3, HIGH);
    delay(100);

    // Initialize GNSS serial
    GNSS.begin(115200, SERIAL_8N1, 33, 34);

    Serial.println("GNSS initialized");
}

void loop() {
    while (GNSS.available()) {
        char c = GNSS.read();
        Serial.write(c);
    }
}

Send Commands

void sendGNSSCommand(const char* cmd) {
    // Calculate checksum
    uint8_t checksum = 0;
    for (int i = 1; cmd[i] != '\0' && cmd[i] != '*'; i++) {
        checksum ^= cmd[i];
    }

    // Send command with checksum
    GNSS.printf("%s*%02X\r\n", cmd, checksum);
}

void configureGNSS() {
    // Enable all GNSS systems
    sendGNSSCommand("$CFGSYS,H11");
    delay(100);

    // Enable GGA and RMC at 1Hz
    sendGNSSCommand("$CFGMSG,0,0,1");
    sendGNSSCommand("$CFGMSG,0,4,1");
    delay(100);

    // Save configuration
    sendGNSSCommand("$CFGSAVE");
}

Parse NMEA

#include <TinyGPS++.h>

TinyGPSPlus gps;

void loop() {
    while (GNSS.available()) {
        if (gps.encode(GNSS.read())) {
            if (gps.location.isValid()) {
                Serial.printf("Lat: %.6f, Lon: %.6f\n",
                    gps.location.lat(),
                    gps.location.lng());
                Serial.printf("Satellites: %d\n",
                    gps.satellites.value());
                Serial.printf("HDOP: %.2f\n",
                    gps.hdop.hdop());
            }
        }
    }
}

Position Accuracy

Parameter	Value
Horizontal (RMS)	1.5 m
Vertical (RMS)	2.5 m
Time (RMS)	5 ns
Velocity	0.02 m/s

Time to First Fix

Mode	Time
Cold Start	< 26 s
Warm Start	< 2 s
Recapture	1 s

Sensitivity

Mode	GPS	BDS	Galileo	GLONASS
Cold Start	-148 dBm	-146 dBm	-144 dBm	-144 dBm
Tracking	-165 dBm	-163 dBm	-163 dBm	-158 dBm