LSM6DSO SPI communication problem

[gabriel.arnautu]

Good morning,

I am trying to read the WHO_AM_I register from LSM6DSO, but it doesn't respond as needed. I will attach a picture from signal analyzer (D0 is CS, D1 is CLK, D2 is MISO, D3 is MOSI). It looks like its respond is 0x50 instead of 0x6C. What should I change?

I tried with a MAX32630 and it was working (8 bits transfer mode).

When I try with RS14100 (16 bits mode) it responds with 0x50 instead of 6C.

Gabriel

[gabriel.arnautu]

It looks like if I am using 1.8V it returns 0x6C which is correct. Does that makes any sense?

[gabriel.arnautu]

I finally found the problem. I was using 1.8V for communication, but my VDDIO was connected to 3.3V

[Eleon BORLINI]

Hi Gabriel, yes, it's recommended that VDD >= VDD_IO, mainly for having well defined VH and VL for the correct SPI data interpretation. Btw do you always use SPI on 8bit, right?

[gabriel.arnautu]

Hi, now I am using SPI on 16 bits and I am trying to make it working like this. I don't know why, but my ARM doesn't want to request the data from the sensor on 8bit SPI.

[S.Ma]

MEMs may boot in SPI 3 wire mode (MOSI short with MISO). Write the control register to switch to 4 wire, then read back in 4 wire mode SPI. Check teh spec

[gabriel.arnautu]

It is 4 wires as I was using it like that before as well.

[Eleon BORLINI]

​Hi kic, if flashed 4-wires (SIM bit in CTRL3_C reg default 0), the sensor always starts 4-wires.

[gabriel.arnautu]

Hi @Eleon BORLINI​ , is there any table with the errors that you can get from the sensor? Now I am getting again 0x50 instead of 0x6C when I read the WHO_AM_I register

[Eleon BORLINI]

​hi Gabriel, did you follow all the Mode1 electrical connection suggestions?

And is this error still related only to RS14100 device? Could you set 8bit communication instead of 16bit on your master?

[gabriel.arnautu]

Hi Eleon, as far as I can see, the problem occurs when I am connecting the same voltage on VDDIO as for VDD, but it shouldn't happen this, right? Now I am using 3.3V for VDD and 1.8V for IO and it looks like is working.

I don't know yet, but I get no answer from sensor if I set the 8bit on master. I raised a ticket to them as well.