Clock Modes

The PULSE supports several clock synchronization modes to ease system level integration. The PULSE sampling state machine can be synchronized to an external clock signal to output IMU data perfectly timestamped and aligned to a GNSS PPS signal for example.

The PULSE supports three clock modes that can be chosen from device settings.

Internal Clock

This is the default mode where the PULSE sampling loop is running using its own internal clock. The host can precisely timestamp the IMU data using a sync out signal.

To use this mode, simply set the /api/v1/settings/clock/source settings to none value.

Please check the How To Articles to learn how to enable the sync out signal.

External Clock Direct Mode

The PULSE sampling loop is directly triggered by an external clock provided by the user. The external clock signal frequency has to match the nominal sampling loop frequency of 2kHz.

The PULSE will only output data if a valid external clock is applied. The input clock as to be stable with no missing clock edge to guarantee correct IMU operation and nominal accuracy.

As soon as the external clock is removed, the PULSE will stop sending data.

Please find below the signal specifications for direct clock mode:

External Clock Scaled Mode

The external input clock signal is scaled to drive the PULSE sampling loop. This mode is perfect to synchronize the PULSE high frequency loop (2kHz) to a low frequency external clock signal such as a GNSS PPS (Pulse Per Second).

In this mode, the PULSE automatically detects the input clock signal period to generate a higher clock of 2kHz to drive the internal sampling loop.

The PULSE implements an algorithm similar to a PLL (Phase Locked Loop) to achieve this.

The input clock has to be stable with no missing edges to use this mode correctly. If you provide a clock that has too much jitter, the PULSE will reject this signal.

The PULSE will start sending data as soon as at least 2 clock edges are received.

As soon as you remove the external clock the PULSE will stop sending data.

Please find below the signal specifications for scaled clock mode: