Skip to main content
AHolt.2
AHolt.2
Associate
January 9, 2020
Question

LPS35HW hanging up

  • January 9, 2020
  • 7 replies
  • 1754 views

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?

This topic has been closed for replies.

7 replies

Eleon BORLINI
Eleon BORLINI
ST Employee
January 13, 2020

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

0690X00000BvvbHQAR.png

AHolt.2
AHolt.2Author
Associate
January 13, 2020

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

0690X00000BvvfEQAR.png

Eleon BORLINI
Eleon BORLINI
ST Employee
January 17, 2020

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
AHolt.2Author
Associate
January 22, 2020

Hi Eleon, any thoughts on this?

AHolt.2
AHolt.2Author
Associate
January 17, 2020

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
AHolt.2Author
Associate
January 30, 2020

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

cheers,

Aaron

Eleon BORLINI
Eleon BORLINI
ST Employee
January 31, 2020

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

Terms & ConditionsAccessibility statement