May I connect CS and SDO/SA0 pins of LIS2DH12/LIS3DH together to the VDD via a 10k resistor?

[tangtangdn]

Hi,

I am designing a PCB board and use LIS2DH12/LIS3DH to wake up the processor. I will use I2C mode (CS pin should be connected to high) and SA0 pad connected to voltage supply (vdd) to get the device address as 0011001b. I see CS is at input high impedance status and SA0 is at internal pull-up status. 

I found a Sparkfun example and it connected CS pin to voltage supply via a 10k resistor, as well as SA0 pin.

 

May I connect CS pin and SDO/SA0 pin together to the VDD via a 10k resistor as shown below?

 

Or, it would be better to connect CS pin to VDD via a 10k resistor, and directly connect SA0 pin to VDD because it has an internal pull-up resistor?

Thank you very much.

Best regards,

Tang 

[Eleon BORLINI · Accepted solution]

Hi Tang @tangtangdn​ ,

consider that the sensors' digital levels are in general referred to the VddIO value, so this is the pull-up reference.

But you tied together Vdd to VddIO, so it is ok as well.

It is basically the same to use a 10kOhm on SA0, or connect it directly to Vdd, since this will in both cases dominate the internal pull-up (from a 10kOhm path ot from a 0 Ohm path). So you can choose accordingly to your application target (I would use the 10kOhm).

As a general suggestion, and if you don't have hardware or resources constrains, it would be better to connect the INTx pins to the application processor too.

If my reply answered your question, please click on Select as Best at the bottom of this post. This will help other users with the same issue to find the answer faster. 

-Eleon

[tangtangdn]

Dear Eleon, thank you so much for your professional reply. Does it mean that INT2 pin also should be connected to the MCU even I only use INT1 pin generated interrupt to wake up the MCU? May thanks.

Tang

[Eleon BORLINI]

Hi Tang,

it is not necessary indeed, but it's recommended.

-Eleon

[tangtangdn]

Hi Eleon, many thanks for your kind help.🙂