PAIR Commands

Comprehensive reference for all PAIR proprietary commands supported by the Quectel LC29H GNSS module family. Derived from the Quectel LC29H GNSS Protocol Specification V1.1, LC29H(BS) Protocol Specification V1.0, and AGNSS Application Note V1.0.

General Format

All PAIR commands follow NMEA-style framing:

$PAIR<CmdID>,<Arg1>,<Arg2>,...*<CS><CR><LF>

Element	Description
$	Start delimiter
PAIR	Talker + sentence identifier
<CmdID>	Three-digit command number (zero-padded)
,	Field separator
*	Checksum delimiter
<CS>	Two-character hex XOR of all bytes between $ and *
<CR><LF>	Carriage return + line feed terminator

Maximum sentence length: 255 bytes (including $ and <CR><LF>).

Checksum Calculation

unsigned char checksum(const char *sentence) {
    unsigned char cs = 0;
    for (const char *p = sentence + 1; *p != '*' && *p; p++)
        cs ^= (unsigned char)*p;
    return cs;
}

Variant Support Key

Abbreviation	Module	Capabilities
AA	LC29H(AA)	SBAS, EASY/EPO, AGNSS
BA	LC29H(BA)	Dead Reckoning + RTK
CA	LC29H(CA)	Dead Reckoning only
DA	LC29H(DA)	RTK only
BS	LC29H(BS)	Base station, raw output

System Commands

PAIR001 — Acknowledgment

Asynchronous response returned by the module after processing any PAIR command. Not sent by the host.

Direction: Module → Host

$PAIR001,<CmdID>,<Result>*<CS>

Result	Meaning
0	Command succeeded
1	Command failed (execution error)
2	Command ID not supported
3	Invalid parameter(s)
4	Command timed out

Variants: All

PAIR002 — Startup Notification

Sent automatically after power-on or restart. Indicates the module is ready.

$PAIR002*38

Variants: All

PAIR003 — Cold Start (Full Reset)

Clear all satellite data and restart. Longest TTFF (~26 seconds).

$PAIR003*39

Variants: All

PAIR004 — Hot Start

Restart using all cached data. TTFF ~1 second when data is valid.

$PAIR004*3E

Variants: All

PAIR005 — Warm Start

Clear ephemeris, retain almanac/position/time. TTFF ~5-10 seconds.

$PAIR005*3F

Variants: All

PAIR006 — Cold Start (Preserve Config)

Same as PAIR003 but retains user configuration (baud rate, fix rate, constellation selection).

$PAIR006*3C

Variants: All

PAIR007 — Factory Reset

Restore all settings to factory defaults and clear all satellite data.

$PAIR007*3D

Caution

Baud rate returns to default (115200). All configuration is lost. Use when module is in an unknown state.

Variants: All

PAIR010 — Query Aiding Status

$PAIR010*3D

Response: $PAIR010,<EPO_Status>,<Time_Status>,<Position_Status>*<CS>

Field	Values
EPO_Status	0 = no EPO data, 1 = available
Time_Status	0 = no time aiding, 1 = available
Position_Status	0 = no position aiding, 1 = available

Variants: AA (primary); DA, BA, CA support time/position fields

PAIR021 — Query Firmware Version

$PAIR021*3A

Response: $PAIR021,<Version>*<CS> (e.g., LC29HAANR11A03S)

Variants: All

GNSS Configuration

PAIR050 — Set Position Fix Rate

$PAIR050,<FixInterval>*<CS>

Field	Range	Default	Unit
FixInterval	100–10000	1000	ms

Examples: $PAIR050,1000*12 (1 Hz), $PAIR050,200*3A (5 Hz), $PAIR050,100*28 (10 Hz)

Note

RTK modes (BA, DA) are typically limited to 1 Hz. Higher fix rates increase power consumption and require higher baud rates.

Variants: All

PAIR051 — Set UART1 Baud Rate

$PAIR051,<BaudRate>*<CS>

Valid values: 4800, 9600, 19200, 38400, 57600, 115200, 921600. Default: 115200.

Caution

After sending, the host must switch to the new baud rate. Use PAIR513 to persist.

Variants: All

PAIR062 — Set DGPS Mode

$PAIR062,<Mode>*<CS>

Mode	Description
0	Off
1	RTCM (for RTK — DA, BA variants)
2	SBAS (AA variant only)

Variants: All (SBAS functional on AA only)

PAIR066 — Set GNSS Constellation

$PAIR066,<GPS>,<GLONASS>,<Galileo>,<BeiDou>,<QZSS>*<CS>

Each field: 0 = off, 1 = on. Default: all enabled.

Examples:

• $PAIR066,1,1,1,1,1*1A — all constellations
• $PAIR066,1,0,0,0,0*1E — GPS only
• $PAIR066,1,0,1,1,1*1B — GPS + Galileo + BeiDou + QZSS

At least one constellation must remain enabled.

Variants: All

PAIR067 — Query Constellation

$PAIR067*3E

Variants: All

NMEA Output Control

Rate parameter: 0 = disabled, 1 = every fix, 2 = every 2nd fix, … N = every Nth fix.

Command	Sentence	Default
PAIR070	GLL	0 (disabled)
PAIR071	RMC	1
PAIR072	VTG	1
PAIR073	GGA	1
PAIR074	GSA	1
PAIR075	GSV	1
PAIR076	GNS	0 (disabled)
PAIR080	ZDA	0 (disabled)
PAIR095	DTM	0 (disabled)

Format: $PAIR07X,<Rate>*<CS>

Variants: All

SBAS Configuration (AA Only)

PAIR382 — Enable/Disable SBAS

$PAIR382,<Enable>*<CS>

0 = disable, 1 = enable (default: 1). Requires PAIR062 mode 2.

SBAS improves accuracy from ~3 m to ~1-2 m CEP in service areas (WAAS, EGNOS, MSAS, GAGAN).

PAIR383 — Query SBAS Status

$PAIR383*35

RTCM Output Configuration (DA, BS)

PAIR432 — Set RTCM Output Mode

$PAIR432,<Mode>*<CS>

Mode	Description
-1	Disabled (default)
0	MSM4 — compact observables (lower bandwidth)
1	MSM7 — full observables (higher precision)

PAIR433 — Query RTCM Output Mode

$PAIR433*3A

PAIR434 — Set RTCM Antenna Reference Point (1005)

$PAIR434,<Enable>*<CS>

Essential for base station operation — provides ARP coordinates to rovers.

PAIR436 — Set RTCM Ephemeris Output

$PAIR436,<Enable>*<CS>

Enables output of messages 1019 (GPS), 1020 (GLONASS), 1042 (BeiDou), 1046 (Galileo).

EASY / EPO — Assisted GNSS (AA Only)

PAIR470 — Query EPO Status

$PAIR470*3A

Response includes EPO coverage per constellation (0-72 hours).

PAIR471 — Inject EPO Data Segment

$PAIR471,<SV>,<Type>,<D0>...<D17>*<CS>

EPO injection is typically automated by QGNSS. Data valid for up to 3 days.

PAIR472 — Erase EPO Data

$PAIR472*38

PAIR490 — Enable/Disable EASY

$PAIR490,<Enable>*<CS>

EASY extends ephemeris validity from ~2-4 hours to ~3 days by predicting orbits. Default: enabled.

PAIR491 — Query EASY Status

$PAIR491*3A

Time and Position Aiding

PAIR590 — Inject UTC Time

$PAIR590,<Year>,<Month>,<Day>,<Hour>,<Minute>,<Second>*<CS>

Time accuracy within 30 seconds is sufficient. Source from host NTP-synced clock.

Variants: All

PAIR600 — Inject Position

$PAIR600,<Latitude>,<Longitude>,<Altitude>*<CS>

Position accuracy within 30 km is sufficient. Combined with PAIR590 for maximum TTFF reduction.

Variants: All

NVRAM / Flash Storage

PAIR511 — Save Navigation Data

$PAIR511*3B

Saves ephemeris, almanac, position, time to flash.

PAIR513 — Save Settings to Flash

$PAIR513*39

Tip

Call after any configuration change (PAIR050, PAIR051, PAIR066, PAIR07X, etc.) to persist across restarts. Batch changes and save once to reduce flash wear.

Power Management

PAIR650 — Enter RTC Backup Mode

$PAIR650*31

Current drops to ~7 uA. Wake by toggling WAKEUP pin (low >100 ms).

PAIR690 — Set Periodic Power Saving

$PAIR690,<Mode>,<RunTime>,<SleepTime>*<CS>

Mode	Behavior
0	Continuous tracking (default)
1	Smart — sleeps but wakes early if fix acquired quickly
2	Strict — fixed duty cycle

Example: $PAIR690,1,1000,3000*XX (1s active, 3s sleep)

Caution

Not recommended during RTK operation — correction stream is interrupted during sleep.

PAIR691 — Query Power Saving Mode

$PAIR691*30

PPS Configuration

PAIR752 — Configure PPS Output

$PAIR752,<Type>,<PulseWidth>*<CS>

Type	Behavior
0	Disabled
1	After first fix (default)
2	On 3D fix only
3	On 2D or 3D fix
4	Always (free-running without fix)

PulseWidth: 1–999 ms (default: 100). PPS accuracy ~10-30 ns when fix is valid.

Raw Measurement Output

PAIR830 — Enable Raw Measurements

$PAIR830,<Mode>*<CS>

Mode	Output
0	Disabled (default)
1	Raw measurements only
2	Raw measurements + SV status + PVT

Variants: BS (primary), DA

PAIR831 — Query Raw Measurement Status

$PAIR831*36

UART Port Configuration

PAIR864 — Set Port Baud Rate

$PAIR864,<PortType>,<PortIndex>,<BaudRate>*<CS>

PortType: 0=UART, 1=I2C, 2=SPI. Provides per-port control vs PAIR051.

PAIR866 — Set Flow Control

$PAIR866,<PortType>,<PortIndex>,<FlowControl>*<CS>

FlowControl: 0=none, 1=XON/XOFF, 2=RTS/CTS (not available on HAT without hardware mod).

Common Configuration Sequences

Initial Setup (All Variants)

$PAIR021*3A                      Query firmware version
$PAIR067*3E                      Query current constellation config
$PAIR066,1,1,1,1,1*1A            Enable all constellations
$PAIR050,1000*12                 Set 1 Hz fix rate
$PAIR073,1*21                    Enable GGA every fix
$PAIR071,1*23                    Enable RMC every fix
$PAIR075,5*24                    GSV every 5th fix (reduce bandwidth)
$PAIR513*39                      Save settings to flash

RTK Rover Setup (DA Variant)

$PAIR062,1*3E                    Enable RTCM DGPS mode
$PAIR066,1,1,1,1,1*1A            Enable all constellations
$PAIR073,1*21                    Enable GGA (required for NTRIP)
$PAIR513*39                      Save settings

RTK Base Station Setup (BS Variant)

$PAIR432,1*3A                    Enable MSM7 RTCM output
$PAIR434,1*3A                    Enable message 1005 (antenna ref)
$PAIR436,1*38                    Enable ephemeris messages
$PAIR513*39                      Save settings
$PQTMCFGSVIN,W,1,3600,1,0,0,0*16   Start survey-in (1hr, 1m accuracy)

Low-Power Tracking (AA Variant)

$PAIR490,1*3A                    Enable EASY for fast reacquisition
$PAIR050,1000*12                 1 Hz fix rate
$PAIR690,1,1000,9000*XX          Smart mode: 1s on, 9s sleep
$PAIR513*39                      Save settings

Reduce Serial Bandwidth

$PAIR070,0*23                    Disable GLL
$PAIR072,0*21                    Disable VTG
$PAIR074,0*27                    Disable GSA
$PAIR075,0*26                    Disable GSV
$PAIR076,0*25                    Disable GNS
$PAIR071,1*23                    Keep RMC
$PAIR073,1*21                    Keep GGA
$PAIR513*39                      Save settings