Why wrong sensor answer on SPI bus?

[mbertoni]

Hi to all.

I correctly set SPI bus as reported on LIS3DSH datasheet:

• Figure 3. SPI slave timing diagram (page 14)
• Figure 7. Read and write protocol (page 25)

Here waveforms:

As first operation I detect sensor reading WHO_AM_I register and getting 0 as output value.

I set wrong SPI bus settings (CLOCK idle value low) and it works.

Why?

Yellow = CS

Green = SDI (data to sensor)

Blue = SCK

Red = SDO (data from sensor)

[Eleon BORLINI]

Hi @mbertoni​ , may it be related to the SPI mode timing you have selected at master level for the decoding of the SPI pattern? Regards

[bmak]

You need to set data word size to 16 bit, so you would have constant 16 clock cycles on SCLK line, now you have 8.