GPS/GNSS Synchronization | Ouster Sensor Docs

This guide will explain how to physically connect a GPS to your Ouster sensor and synchronize the Ouster sensor timestamp to an NMEA sentence.

Setting up your GPS/GNSS

It is important to ensure you have configured your GPS according to the manufacturer’s specifications.

The Ouster sensor accepts the following:

NMEA sentence type: GPRMC only (future support for other sentence types)
Baud Rates: 9600 or 115200
Polarity: Normal or Reversed (ACTIVE_HIGH¹ or ACTIVE_LOW²)
Voltage: 3.3 - 15 V logic with a minimum drive current of 5 mA.
- If your GPS can’t meet these minimums you will need to buffer the voltage with an additional circuit. Details in the Digital IO section of the Ouster Hardware User Manual.

ACTIVE_HIGH - Low to high edge as critical timing event
ACTIVE_LOW - High to low edge as critical timing event

Once you have configured your GPS, it is good practice to verify the signals using an oscilloscope. This will ensure you have the correct baud rate, polarity, voltage, and message type being output.

Connecting the Hardware

The next step to successfully connecting your GPS is ensuring that you have connected the outputs from your GPS to the correct inputs of the sensor.

Connection using the GPS Port

Connect the PPS output from GPS to the sync_pulse_in pin of the GPS connector to be plugged on the Ouster Interface Box.
Connect the NMEA UART output from GPS to the multipurpose_io pin of the GPS connector to be plugged on the Ouster Interface Box.
Connect the ground output from GPS to the GND pin of the GPS connector to be plugged on the Ouster Interface Box.

Connection using the Pin out

Connect the PPS output from GPS to the sync_pulse_in pin of the Ouster Interface Box.
Connect the NMEA UART output from GPS to the multipurpose_io pin of the Ouster Interface Box.
Connect the ground output from GPS to the GND pin of the Ouster Interface Box.

Based on the type of interface box being used please refer to either High Current Modular Interface Box (PCBA PN- 830-103125) or High Current Interface Box (PCBA 830-104249) - Standard.

SYNC_PULSE_IN Interface Requirements

Parameter	Min Voltage	Max Voltage	Min Driver Current
LOGIC LOW	-30 V	2 V	N/A
LOGIC HIGH	2.9 V	30 V	3mA @3.3V~5V, 5mA at 24V and higher

MULTIPURPOSE_IO - INPUT Interface Requirements

Parameter	Min Voltage	Max Voltage	Min Driver Current
LOGIC LOW	-30 V	2 V	N/A
LOGIC HIGH	2.9 V	30 V	3mA @3.3V~5V, 5mA at 24V and higher

Configuring the Ouster Sensor

Please refer to the GPS configuration section in the firmware user manual to configure your sensor to synchronize its timestamp with the GPS.

Support

In case of any questions regarding the contents of this user manual or the configuration of the sensor, please contact Ouster Support or visit Ouster website.