LSM6DS3 EVB "STEVAL-MKI160V1" communication issue with WHO AM I

SChin.2 · ‎2021-03-22

Hi ST

we are seeing wrong response for WHO AM I command,

SPI Configuration:

SPI Freq- 100KHZ
Slave Select - Active low
CPHA- 1
CPOL - 1
bit order - MSB first

sent 0x8F00 on MOSI line and seen 0x0040 and it was random some times we are seeing 0x007F as a response. can you please help us on this

SChin.2 · ‎2021-03-25

Hello @Eleon BORLINI

found the root cause for it, MISO line is with high impedance , just need to place the resistance to avoid reflections on the line. In my case we have added 20ohms resistor is added.

View solution in original post

SChin.2 · ‎2021-03-23

Can some one help me on this please !

SChin.2 · ‎2021-03-23

Hi @Eleon BORLINI

Can you please help me on this, as this is on high priority for me and we are blocked with this.

Eleon BORLINI · ‎2021-03-23

Hi @SChin.2 ,

No guess so far, the CS, CLK and MOSI lines looks OK. MISO line and Channel 3 (I suppose it is the scope waveform). not so good...

For this reason, I'm wondering if it could be an "hardware" problem. Did you correctly set all the pins from the application processor side, and in particular the SCx and SDX pins, as stated in the datasheet p.9?

-Eleon

SChin.2 · ‎2021-03-23

Hello @Eleon BORLINI

Are you refereeing me to P.19 (Table 2. Pin description).

Here my connections description :

VDDIO-->3.3V

VDD-->3.3V

GND-->GND

CS--> Chip Select of MC

SCL-->Clock of MC

SDA-->serial data output line of MC

SDO-->serial data input line of MC

Reset all pins are left not connected (NC)

Eleon BORLINI · ‎2021-03-23

Please note that the SDx and SCx pins (in Mode 1 function, i.e. LSM6DS3 slave configuration) have to be connected to VDDIO or GND, even if they are not used.

-Eleon

SChin.2 · ‎2021-03-23

how about other two pins ? OCS, OSDO

Can be left not connected ?

SChin.2 · ‎2021-03-23

Hello @Eleon BORLINI

I have just tied the SCx & SDx lines to GND and verified by reading WHO AM I register, am seeing 0x007F as a response constantly.

For your info clock is at 1Mhz

Eleon BORLINI · ‎2021-03-23

The OCS and OSDO lines refer to the other device on the STEVAL-MKI160V1, so no problem.

Try with 8 bit per transfer, I'm running out of ideas...

-Eleon

SChin.2 · ‎2021-03-23

As I expected am seeing response 0x0000 for 8bit transfers. Is their any other way to verify the device functionality or communication ?