Using General-purpose input configuration register for ISPU (LSM6DS016IS)

[Amith_lal]

I am developing firmware for the ISPU on the LSM6DSO16IS and have a question regarding communication between the host MCU and the ISPU core.

My objective is to persist magnetometer calibration data. My intended workflow is:

1. The ISPU runs the MotionMC_update function and calculates the HI_bias values.

2. The host MCU reads these HI_bias values from the ISPU's output registers and saves them to non-volatile memory.

3. On the next device startup, the host MCU writes the saved HI_bias values into the ISPU_DUMMY_CFG registers, intending for the ISPU to use them as initial calibration data.

I have successfully implemented step 3. I can write to the ISPU_DUMMY_CFG_1 register from my external STM32 host using the lsm6dso16is_ispu_write_dummy_cfg() function, and I can verify the write was successful by reading it back from the host with lsm6dso16is_ispu_read_dummy_cfg().

The problem occurs when the ISPU firmware itself tries to read this value. When I attempt to read the ISPU_DUMMY_CFG_1 register from within the ISPU code, it always returns 0x0000, not the value written by the host.

Here is the simplified code snippet from my ISPU algo_00_init function that demonstrates the issue:

uint16_t read_value = 0;

read_value = cast_uint16_t(ISPU_DUMMY_CFG_1);

Since the register is clearly accessible from the external host but not readable by the ISPU core, I suspect there may be a specific initialization step or access permission I am missing within the ISPU firmware to enable this communication path.

i refered https://github.com/STMicroelectronics/ispu-examples/blob/1ce408f7837e9afa4a6ffded9daf6376e3a81647/ism330is_lsm6dso16is/sensor_fusion_9x/ispu/src/main.c

Could you please advise on the correct procedure for the ISPU to read the ISPU_DUMMY_CFG registers after they have been set by a host MCU?

[Federica Bossi]

Hi @Amith_lal ,

The description of how to read the ISPU_DUMMY_CFG registers is provided in section 9.5 of the application note. The method you are using to read the first register is correct.

When do you write to the ISPU_DUMMY_CFG registers and perform the readback in relation to loading the ISPU program? Writing the ISPU_DUMMY_CFG registers before loading the program ensures correct functionality.