MEMS Studio: Raw QVAR Signal on Nucleo STM32F401RE & X-NUCLEO-IKS4A1

[mariagragna]

Hello,

I have the Nucleo STM32F401RE board, on which I mounted the X-NUCLEO-IKS4A1 expansion board with the removable add-on STEVAL-MKE001A for QVAR signal detection.

My first question is: is it possible to acquire the raw QVAR signal using only MEMS Studio, or is it necessary to integrate a firmware solution? By "raw QVAR signal," I mean the data that has not been processed by the FSM, and not the tap or double tap, which serves only as an interrupt.

Below are the steps I have followed so far and the inconsistencies I encountered:

1. When connecting the board to the PC, the software immediately recognizes it, and using the provided DataLogExtended binary, I can select the devices of interest, including the LSM6DSV16X IMU for QVAR signal acquisition.
2. In the register interface, I configured:
- The `AH_QVAR_EN` bit to 1 in the `CTRL7` register (16h).
- The `INT2_DRDY_AH_QVAR` bit to 1 in the `CTRL7` register (16h).
- Wrote the values `(0x10, 0x07)`, `(0x11, 0x07)`, and `(0x16, 0xC0)`.

I encountered two main issues:
- The first concern relates to reading via `MultiRead (0x3A, (uint8_t*)&qvar_out, 2)`. In the interface, it is only possible to interact with address `0x3A` or `0x3B`, as if reading the entire word is not allowed.
- Additionally, I noticed that the datasheet specifies that the accelerometer must be turned on in high-performance or normal mode, while MEMS Studio indicates that both the accelerometer and gyroscope should be configured in power-down mode (I have attached a screenshot).

I also tried enabling the pull-up resistor by setting `SHUB_PU_EN = 1` in the `IF_CFG` register (03h), but without success.

In both cases, even after programming the board, I cannot visualize a time-varying signal in the graphs. Either I cannot acquire the signal, or the acquired value remains fixed at -420.103, without responding to interactions with the electrodes.

What am I doing wrong? I would like to acquire the raw signal to study it and then use the FSM. I don’t want to limit the use of QVAR only to handle interrupts.

Thank you in advance for your help.

[Miroslav BATEK]

Hello @mariagragna,

Yes, it possible to acquire the raw QVAR signal using only MEMS Studio and DatalogExtended firmware.

First of all you have to configure the X-NUCLEO-IKS01A4 to connect the electrodes to the LSM6DSV16X. The configuration is described in Getting started with the X-NUCLEO-IKS4A1 or see following image.

Then you should click on Enable AH_Qvar in Quick Setup page. The sensor configuration is done by the application. The power modes are managed automatically by the firmware. You don't have to manually write any configuration into the registers.

After that you will get the QVAR data.

Please keep in mind some registers are controlled by the firmware so your modification can interfere with the firmware. This is the case you see the accelerometer and gyroscope and in power down mode. It is because the sensor temporality stopped when reading/writing to sensor registers.