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LSM6DSV16X – I²C Communication Fails

Taksh
Associate III

‎2025-11-05 5:04 AM

Hello ST Community,

I am currently working on integrating the LSM6DSV16X accelerometer with an STM32H7 series MCU over I²C.
 Our main goal is to detect the tilt angle of the system.

 

Hardware Setup

  • MCU: STM32H7

  • Sensor: LSM6DSV16X (mounted on a custom board)

  • Interface: I²C

  • SA0 Pin: Pulled high → I²C address = 0x6B

  • Power Supply: 3.3 V

  • Pull-ups: 4.7 kΩ on SDA and SCL lines

  • I²C Speed: Tested at both 100 kHz and 400 kHz

 

The setup is straightforward — the sensor is connected to the STM32H7’s I²C1 bus, and it can be successfully detected using an I²C scanner.

 

I’m using the official STMicroelectronics driver from this repository:

https://github.com/STMicroelectronics/STMems_Standard_C_drivers/blob/master/lsm6dsv16x_STdC/examples/lsm6dsv16x_self_test.c 

 

However, I’m facing an unusual issue during normal operation.

 

Issue Description

When I try to read the WHO_AM_I register using the official LSM6DSV16X driver, I get inconsistent results.

 

Case 1 – Normal Run (no breakpoints)

  • HAL_I2C_Mem_Read() returns HAL_ERROR

  • WHO_AM_I value = 0x00

  • Failure occurs inside:

if (I2C_WaitOnTXISFlagUntilTimeout(...) != HAL_OK)
    return HAL_ERROR;

 

Case 2 – With Debugger Breakpoint (1s delay before read)

  • Communication works perfectly

  • WHO_AM_I value = 0x70

  • The LSM6DSV16X is detected successfully

It seems that communication only succeeds when a manual delay or breakpoint is added before the I²C transaction.

 

What I’ve Verified So Far

I²C scanner detects the device at address 0x6B (correct SA0 configuration)
Pull-ups and wiring verified – no shorts, clean signal levels
Tested with both 100 kHz and 400 kHz I²C speeds
HAL I²C initialization succeeds
Using official ST driver functions (lsm6dsv16x_device_id_get())

 

 

Example Logs

[17:28:28:084] Scanning I2C bus...
[17:28:28:094] Found device at address 0x6B
[17:28:28:098] Found device at address 0x7E
[17:29:08:877] WHO_AM_I: 0x70
[17:29:33:614] WHO_AM_I: 0x00
[17:29:33:616] Unknown device! WHO_AM_I = 0x00

 

 

Questions

  1. Why does I²C communication (especially HAL_I2C_Mem_Read) fail unless a manual delay is inserted before accessing the registers?

  2. Is there a specific startup or boot delay required after powering up the LSM6DSV16X before register access?

  3. Are there any known timing or synchronization issues between the STM32H7 I²C peripheral and the LSM6DSV16X?

  4. For tilt angle detection (±60° range), is the LSM6DSV16X suitable for directly computing pitch and roll angles from accelerometer data?

 

 

Expected Behavior

  • The WHO_AM_I register should consistently return 0x70 without requiring any artificial delay.

  • The sensor should be fully ready for I²C communication as soon as power and I²C lines are stable.

 

Summary

It appears there may be a timing or readiness issue between the LSM6DSV16X startup and the first I²C transaction.
Any guidance on the proper initialization sequence, recommended power-up delays, or I²C timing adjustments would be greatly appreciated.

 

 

Best regards

Taksh Patel

 

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