GNSS Config

Updated on Aug 29, 2026

The GnssConfig struct controls all module settings. It is passed to start() at initialization.

C++

GnssConfig config {
    .measurementRate_Hz = 1,
    .dynamicModel = EDynamicModel::Stationary,
    .timepulsePinConfig = TimepulsePinConfig { ... },
    .geofencing = std::nullopt,
    .rtk = std::nullopt,
    .timing = std::nullopt,
    .saveToFlash = false
};
hat->start(config);

jp_gnss_gnss_config_t config;
jp_gnss_gnss_config_init(&config);
config.measurement_rate_hz = 1;
config.dynamic_model = JP_GNSS_DYNAMIC_MODEL_STATIONARY;
// ... set fields ...
jp_gnss_hat_start(hat, &config);

Python

config = {
    'measurement_rate_hz': 1,
    'dynamic_model': gnsshat.DynamicModel.STATIONARY,
    'timepulse_pin_config': { ... },
    'geofencing': None,
    'rtk': None,
    'timing': None
}
hat.start(config)

Fields

Field	C++ Type	Description
`measurementRate_Hz`	`uint16_t`	GNSS measurement rate, 1–25 Hz
`dynamicModel`	`EDynamicModel`	Receiver motion model — affects filtering and accuracy. See Dynamic Models
`timepulsePinConfig`	`TimepulsePinConfig`	Time pulse output on GPIO 5. See Timepulse
`geofencing`	`optional<Geofencing>`	Up to 4 geofences. See Geofencing Config. Not on TIME HAT
`rtk`	`optional<RtkConfig>`	RTK mode (Base/Rover). See RTK Config. RTK HAT only
`timing`	`optional<TimingConfig>`	Time mark and time base. See Timing Config. TIME HAT only
`saveToFlash`	`bool`	Save configuration to u-blox flash memory. Default: `false`

Note
Required Fields — measurementRate_Hz, dynamicModel, and timepulsePinConfig are always required. The remaining fields are optional and HAT-specific.

Measurement Rate

Valid range: 1–25 Hz. The library validates this before sending to the module.

Rate	Use Case
1 Hz	General navigation, timing, low power
5 Hz	Walking, cycling, driving
10 Hz	Fast automotive, drone
25 Hz	High-dynamics applications

Note
Higher rates increase CPU and SPI/UART bus load. At 25 Hz on the L1 HAT (SPI), expect ~15% CPU usage on a Raspberry Pi 4.

Validation

The library validates configuration before sending it to the module:

measurementRate_Hz must be 1–25
timepulsePinConfig.pulseWidth must be 0.0–0.99
Geofencing requires 1–4 geofences with valid coordinates
Base config (RTK/Timing) requires valid Survey-In parameters or coordinates

If validation fails, start() returns false.