LPS35HW hanging up

[AHolt.2]

We have a design with LPS35HW where the part sometimes doesn't respond on the SPI bus at startup. A power cycle clears the issue. Any ideas on what could cause this?

[Eleon BORLINI]

Hi @AHolt.2​ , at which Vdd and VddIO are you working? Can you share the schematic of that LPS35HW circuit portion? Is it equivalent to this one? Regards

[AHolt.2]

Hi Eleon, for this design VDD = VDDIO = 3.3V. We are using the SPI interface. The schematic is as below:

[Eleon BORLINI]

Hi @AHolt.2​ , thank you for sharing the schematic picture. The fact that the LPS35HW doesn't respond to an SPI START instruction could be related to the BAR_SPI_CS status, which is pull-upped to VCC_3V3: if it remains high, the SPI communication doesn't start. Did you check the CS is working well (e.g. with an oscilloscope)? Regards

[AHolt.2]

Hi Eleon, any thoughts on this?

[AHolt.2]

Hi Eleon, the SPI bus functions normally 99.9% of the time. We have no problem with that. There are however situations where the device does not response to an SPI read on power up. Doing a power cycle will restore proper operation.

cheers,

Aaron

[AHolt.2]

Hi Eleon, do you think that perhaps the device gets stuck in i2c mode somehow?

cheers,

Aaron

[Eleon BORLINI]

Hi @AHolt.2​ , according to my experience, the SPI protocol is more robust than the I2C one... what I would suggest you is to write 1 in the I2C_DIS bit of CTRL_REG2 (11h) register (p. 34 of the datasheet). This is a this is an additional precaution to avoid any possible cross talk. Regards