Xiao nRF52840 Sense - problem with LSM6DS3 latching

Products & Technology XIAO
1

Hi, I think I managed to successfully setup 6D orientation interrupt with LSM6DS3 using INPUT_PULLDOWN_SENSE, however for some reason latching doesn’t seem to work even though I enable it. The device resets upon receiving interrupt, but the state of LSM6DS3_ACC_GYRO_D6D_SRC register seems to always be zero… Anyone could help me out there?

#include <nrf52840.h>

#include "LSM6DS3.h"
#include "Wire.h"

#define int1Pin PIN_LSM6DS3TR_C_INT1

LSM6DS3 lsm6ds3(I2C_MODE, 0x6A);    
volatile uint16_t detectCount = 0;

void blinkLED(int ledPin, int interval, int numBlinks) {
  for (int i = 0; i < numBlinks; i++) {
    digitalWrite(ledPin, HIGH);
    delay(interval);
    digitalWrite(ledPin, LOW);
    delay(interval);
  }
}


void setup() {
    uint8_t readDataByte = 0;
    int initError = lsm6ds3.begin();

    pinMode(PIN_LSM6DS3TR_C_INT1, INPUT_PULLDOWN_SENSE);
    lsm6ds3.readRegister(&readDataByte, LSM6DS3_ACC_GYRO_D6D_SRC); 

    pinMode(LED_BUILTIN, OUTPUT);
    blinkLED(LED_BUILTIN, 100, 3);

    Serial.begin(9600);
    while(!Serial);

    if (initError != 0) {
        Serial.println("Device error");
    } else {
        Serial.println("Device OK!");
    }

    Serial.print("Register:");
    Serial.println(readDataByte);
    readDataByte &= 0x40;
    if (readDataByte) {
        detectCount ++;
        Serial.println("ANGLE CHANGED");
        blinkLED(LED_BUILTIN, 100, 20);
    } 
    delay(1000);

    if (0 != configure_angle()) {
        Serial.println("Fail to configure!");
    } else {
        Serial.println("Success to Configure!");
    }
    delay(1000);
    //Reset the latch before sleep
    lsm6ds3.readRegister(&readDataByte, LSM6DS3_ACC_GYRO_D6D_SRC); 

    pinMode(PIN_LSM6DS3TR_C_INT1, INPUT_PULLDOWN_SENSE);
    // nrf_gpio_cfg_sense_input(digitalPinToInterrupt(PIN_LSM6DS3TR_C_INT1), NRF_GPIO_PIN_PULLDOWN, NRF_GPIO_PIN_SENSE_HIGH);
  
    attachInterrupt(digitalPinToInterrupt(PIN_LSM6DS3TR_C_INT1), int1ISR, RISING);
    // nrf_gpio_cfg_sense_input(digitalPinToInterrupt(PIN_LSM6DS3TR_C_INT1), NRF_GPIO_PIN_PULLDOWN, NRF_GPIO_PIN_SENSE_HIGH);

    Serial.println("Sleeping...");
    digitalWrite(LED_BUILTIN, HIGH);
    Serial.flush();

    NRF_POWER->SYSTEMOFF = 1;
}

void int1ISR() {
  detectCount ++;
}

void loop() {
}

int configure_angle(void) {
    uint8_t error = 0;
    uint8_t dataToWrite = 0;

    dataToWrite |= LSM6DS3_ACC_GYRO_BW_XL_50Hz;
    dataToWrite |= LSM6DS3_ACC_GYRO_FS_XL_2g;
    dataToWrite |= LSM6DS3_ACC_GYRO_ODR_XL_13Hz;

    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_CTRL1_XL, dataToWrite);
    
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_TAP_CFG1, 0x81);
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_TAP_THS_6D, 0xc0); // c0 11000000 d4d enable, 60 degrees
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_CTRL8_XL, 0x01); // low pass
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_MD1_CFG, 0x04);

    return error;
}
2

Hi there,

And welcome here,

So I looked , compiled and tested …
Your code is mostly correct but has a few potential issues and areas for improvement:

Issues & Fixes

  1. Incorrect Interrupt Pin Definition
  • #define int1Pin PIN_LSM6DS3TR_C_INT1 is defined but never used.
  • Instead, you directly use PIN_LSM6DS3TR_C_INT1. Make it consistent.
  1. Missing int1ISR Declaration Before attachInterrupt
  • Ensure void int1ISR(); is declared before setup() to avoid implicit declaration warnings.
  1. Interrupt Pin Configuration Conflicts
  • pinMode(PIN_LSM6DS3TR_C_INT1, INPUT_PULLDOWN_SENSE); is used before attachInterrupt().
  • Fix: Configure the pin once before attaching the interrupt to avoid redundant calls.
  1. Unnecessary Second pinMode() for PIN_LSM6DS3TR_C_INT1
  • You’re configuring PIN_LSM6DS3TR_C_INT1 twice—once in setup() and again before attachInterrupt(). The second instance can be removed.
    5. Writing to Power Off System Without Explicit Sleep Mode Setting
  • NRF_POWER->SYSTEMOFF = 1; immediately powers off the system.
  • Ensure everything (including Serial output) is completed before this call.
  1. configure_angle() Return Type Handling
  • error is returned but never checked in setup() after the function call. You should handle errors properly.

I see , The issue could be due to several factors:

  1. Latching Not Working: The LSM6DS3_ACC_GYRO_D6D_SRC register should retain its value until it’s read, but if latching isn’t working, the flag might reset before you can check it.
  • Ensure LSM6DS3_ACC_GYRO_TAP_CFG1 has 0x81 (latching enabled).
  • Try explicitly setting LSM6DS3_ACC_GYRO_CTRL3_C to enable block data update (BDU).
  1. Reset on Interrupt: If the board resets when an interrupt occurs:
  • Check if the ISR (int1ISR()) is too complex or calling non-ISR-safe functions.
  • Use volatile variables only and avoid Serial prints inside ISR.
  1. Interrupt Pin Configuration: Ensure PIN_LSM6DS3TR_C_INT1 is correctly configured as INPUT_PULLDOWN.
  2. Confirm 6D Orientation Mode: Verify if CTRL8_XL and TAP_THS_6D are set correctly for 6D detection.

Try adding a small delay before reading D6D_SRC to see if the flag is resetting too quickly.

It took a few tries , but this works like you describe.

#include "LSM6DS3.h"
#include "Wire.h"

#define INT1_PIN PIN_LSM6DS3TR_C_INT1  // Interrupt pin

LSM6DS3 lsm6ds3(I2C_MODE, 0x6A);    
volatile uint16_t detectCount = 0;

void int1ISR() {
    detectCount++;
    Serial.println("Interrupt Triggered!");
}

void blinkLED(int ledPin, int interval, int numBlinks) {
    for (int i = 0; i < numBlinks; i++) {
        digitalWrite(ledPin, HIGH);
        delay(interval);
        digitalWrite(ledPin, LOW);
        delay(interval);
    }
}

void setup() {
    Serial.begin(9600);
    while (!Serial);

    pinMode(INT1_PIN, INPUT_PULLDOWN);
    pinMode(LED_BUILTIN, OUTPUT);
    blinkLED(LED_BUILTIN, 100, 3);

    if (lsm6ds3.begin() != 0) {
        Serial.println("Device error");
        return;
    }
    Serial.println("Device OK!");

    if (configure_angle() != 0) {
        Serial.println("Failed to configure!");
    } else {
        Serial.println("Successfully Configured!");
    }

    // Enable Latching of 6D Orientation Interrupt
    uint8_t ctrl3C;
    lsm6ds3.readRegister(&ctrl3C, LSM6DS3_ACC_GYRO_CTRL3_C);
    ctrl3C |= 0x40;  // Set LIR bit to latch interrupt
    lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_CTRL3_C, ctrl3C);

    // Clear Latch
    uint8_t dummy;
    lsm6ds3.readRegister(&dummy, LSM6DS3_ACC_GYRO_D6D_SRC);

    attachInterrupt(digitalPinToInterrupt(INT1_PIN), int1ISR, RISING);
    Serial.println("Interrupt configured. Waiting for motion...");
}

void loop() {
    uint8_t status;
    lsm6ds3.readRegister(&status, LSM6DS3_ACC_GYRO_D6D_SRC);

    if (status & 0x40) {  // Check 6D Orientation interrupt flag
        Serial.println("6D Orientation Change Detected!");
        blinkLED(LED_BUILTIN, 100, 5);

        // Clear Latch by reading register
        lsm6ds3.readRegister(&status, LSM6DS3_ACC_GYRO_D6D_SRC);
    }

    delay(500);
}

int configure_angle(void) {
    uint8_t error = 0;
    uint8_t dataToWrite = 0;

    dataToWrite |= LSM6DS3_ACC_GYRO_BW_XL_50Hz;
    dataToWrite |= LSM6DS3_ACC_GYRO_FS_XL_2g;
    dataToWrite |= LSM6DS3_ACC_GYRO_ODR_XL_13Hz;

    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_CTRL1_XL, dataToWrite);
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_TAP_CFG1, 0x81);
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_TAP_THS_6D, 0xC0);
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_CTRL8_XL, 0x01);
    error += lsm6ds3.writeRegister(LSM6DS3_ACC_GYRO_MD1_CFG, 0x04);

    return error;
}

I used BSP 1.1.9 , I think #5 is also the reason. so.:+1:
HTH
GL :slight_smile: PJ :v:

Serial output:

Device OK!
Successfully Configured!
Interrupt configured. Waiting for motion...

Interrupt Triggered!
6D Orientation Change Detected!

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