LSM6 Wakeup on Gyro-Z Threshold

[Yashu]

In the past, I have used an LSM330 to wakeup on a gyro z-axis threshold and activate the INT1 pin as shown below:

Gyro_WrByte(GYRO_CTRL_REG1, 0x3f); // 95Hz DataRate : 25Hz Cutoff : Normal Mode : Enable All Axes
Gyro_WrByte(GYRO_CTRL_REG2, 0x07); // HPF Normal Mode : 0.045Hz HPF Cutoff Freq : HPF Normal Mode
Gyro_WrByte(GYRO_CTRL_REG3, 0x80); // INT on INT1_Gyro Pin
Gyro_WrByte(GYRO_CTRL_REG4, 0x00); // Continuous Update : Little Endian Data : 250 dps FS : 4-Wire SPI Intfc
Gyro_WrByte(GYRO_CTRL_REG5, 0x04); // Normal Mode Reboot Mem Content : FIFO Disable : HPF Disabled : INT1 Select = 01b : OUT Select = 0 : Use HPF for INT1 to account for any incr gyro bias drift due to incr temperature

Gyro_WrByte(GYRO_INT1_CFG, 0x20);      // OR Combination : Z-High Event
Gyro_WrByte(GYRO_INT1_TSH_ZL, 0x3b);   //
Gyro_WrByte(GYRO_INT1_TSH_ZH, 0x02);   // Z-Threshold = 571(0x023b) * 8.75mdps = 5Deg/s
Gyro_WrByte(GYRO_INT1_DURATION, 0x8a); // WAIT Enable : INT Duration = 10(0x0a) * 1/95Hz = 100msec

 

Since LSM330 has been discontinued, can an LSM6 device be used to perform this same functionality? If so, which device variant is sufficient?

Thank you.

[Federica Bossi]

Hi @Yashu ,

 

Have you already looked at LSM6DSV16X?

[Yashu]

The LSM6 reg sets are not as concise as the LSM330. I do not see a specific way to choose the gyro as the WAKE_UP_SRC as opposed to the accel. WK_THS only seems to reference accel thresholds.

Am I to assume that the source thresholds are with respect to whatever MEMS structure is enabled via CTRLxx ?

Or is it not possible to wake on a gyro threshold and therefore ST has dropped this capability in their "offerings" ?

[Federica Bossi]

Hi @Yashu ,

On LSM6‑series devices the wake‑up function is accelerometer‑based only: WAKE_UP_THS and WAKE_UP_SRC do not support direct gyro threshold as in LSM330.

A pure “hardware wake on gyro threshold” path like LSM330 is no longer available. The usual options are:

• use accel wake‑up to bring the MCU out of low‑power, then check gyro Z in firmware, or
• on devices with FSM/MLC (e.g. LSM6DSOX, LSM6DSV16X), implement a small FSM that monitors the gyro and generates an interrupt.