LIS3DE vs. LIS3DH HW FIFO Handling

[Martin Lampacher]

Posted on June 11, 2018 at 14:55

Hello,

we've been using the LIS3DH on a development board and have switched to the LIS3DE for the prototype. We're using the HW fifo feature to batch-read values from the sensor. The LIS3DE is only 8-bit and thus I was expecting the HW fifo to only provide 8-bit values, but it seems like it is still sending 2 bytes per axis, is this correct?

The reason I'm asking is simply due to the fact that the _L and _H distinction does not exist on the LIS3DE, I'm always reading from register 0x29 (instead of 0x28) and read using auto-increment. In the received data every second value is zero and thus the values are actually signed 16 bit values?

What is the correct way to interpret the values? Attached: Buffer as read from LIS using HW fifo feature

#fifo-buffer #lis3dh #lis3de

[Miroslav BATEK · Accepted solution]

Posted on June 18, 2018 at 16:27

It is correct, there are two bytes in the FIFO per axis. But the second byte is not used so you can discard it.

[Martin Lampacher]

Posted on June 18, 2018 at 17:52

Thanks, I did fear that this might be the answer since it doubles the amount of data that i have to transmit via I2C. another question very closely related to this: The LIS3DE also has a 'normal' mode (vs. 'low-power') but always delivers 8-bit values - is there really any difference between these two?

On the LIS3DH the device provides 10 bit in normal mode (instead of 8 bit). The only option affected by this setting on the LIS3DE is the 1.6 kHz mode - is this correct or is there any other use of the normal mode on the LIS3DE?

[Miroslav BATEK]

Posted on June 19, 2018 at 16:40

First difference is the available ODR modes:

Second difference is in current consumption:

In Normal mode the noise will be lower because the sensor does internally an averaging.

[Martin Lampacher]

Posted on June 19, 2018 at 21:58

Thank you for the clarification !