LPS22HB I2C communication error due to pin3 ?

[DBhav.1]

Hello,

We are developing a STEM-based educational product. We have just received our initial test PCB for V2.

In our PCB for sensing the pressure, we have used an LPS22HB pressure sensor, I am attaching the circuit diagram used for the LP22HB in the PCB.

We are using ESP32-Wroom32d as a controller and I2C communication to communicate with the LPS22HB. But unfortunately, we are not able to communicate with the LPS22HB. After a lot of tests and failed attempts, we tried a simple I2C scanner code to check if there is any I2C address-related issue. But the results of the I2C scanner were shocking to us like all the rest I2C based sensors were showing their address properly except the LPS22HB. That means it is not even communicating over I2C. Here is the image of the I2C scanning result. All different sensors are showing their address except the pressure sensor.

 

After taking a closer look at the datasheet again we noticed about the pin3 of LPS22HB. Pin description table tells that we need to connect this pin to GND.

  

Also in the reference circuit pin-3 is connected to GND. Apart from this circuit and pin description, there is no such detail in the datasheet that what will go wrong if pin-3 is not connected to the ground.

 

Therefore we come to the conclusion that there will be the following possible reasons for the IC not communicating properly.

1) As in our PCB we have not connected pin-3 to GND that's why it is not working properly.

2) PCB assembly error ( We don't think this might be a problem as we tested the same I2C scanner in multiple PCBs but the results were the same but still considering it).

Therefore we need some sort of confirmation for this error before heading towards our next prototype PCB.

If this is error is caused due to pin 3 then I think there is no problem we can easily connect to the ground and also suggest updating the datasheet regarding pin 3 importance of connecting to GND.

And if this is not the case then need help to understand the real cause of the error before proceeding towards the next PCB version.

Thank You,

Dharmik Patel.

[JWu.12]

Hi Dharmik, interesting project indeed! You actually need to tie the RES pin to GND for a proper operation of the device, as specified in the datasheet. Do you have the possibility to connect it to GND for a definitive test that excludes other kind of issues (I suppose not, but asking as well)?

[DBhav.1 · Accepted solution]

Hello,

That's the problem that this sensor is so small and pads are also small that I am not able to connect the RES pin with GND for confirming the issue.

In the next version, I will definitely connect it with GND but it will be better if I get a better picture of the error before proceeding to the next version.