Datasheet seems incomplete for LSM303DLHC

Adam Hamilton · ‎2018-02-15

Posted on February 16, 2018 at 04:29

I am trying to develop a driver for my project which uses this Accelerometer / e-compass and while there is plenty of information for me to get something working, it is missing some information and some information is just not correct.

I would specifically like to add support for high pass filtering but I have no idea what HPCF[2:1] does - there was mention by someone at Pololu that the LSM303DLM datasheet has this information but can I fully trust that these filter coefficients are the same?

There was also mention of 2 data ready signals as quoted from the revision 2 datasheet on page 16

The LSM303DLHC features two data-ready signals (RDY) which indicate when a new set of

measured acceleration data and magnetic data are available, therefore simplifying data

synchronization in the digital system that uses the device.

There is only one externally accessible DRDY signal, however there are two interrupt lines. There also doesn't seem to be any information on the DRDY signal. Is this asserted when there is data available on the X,Y,Z registers, how about FIFO? Magnetometer data?

I can probably deduce the DRDY pin use from selective disablement of the accel/mag so I am not too concerned with that.

So my questions are:

Is there any errata to this datasheet
Can I rely on using the other more complete datasheet mentioned earlier to cherry pick the information

Thanks all for your time

#lsm303dlhc

Miroslav BATEK · ‎2018-02-16

Posted on February 16, 2018 at 10:34

1. No there is no errata to the datasheet.

2. I would not recommend you to use other datasheet, even it the devices looks similar there could be differences.

Concerning the high pass filter cut-off frequencies (HPCF[2:1] bits) I can try to get the values.

The DRDY pin is data ready signal from the magnetometer only.

The INT1 and INT2 pins can be configures using CTRL_REG3_A (22h) and CTRL_REG6_A (25h) registers.

Where you can select which signals will be available on the pins (Data ready from accelerometer, threshold interrupt, FIFO watermark, ...)

I would also like to mention, that the LSM303DLHC is not recommended for new design, there are newer and better sensors.

Adam Hamilton · ‎2018-02-16

Posted on February 16, 2018 at 13:54

Hi Miroslav

I wouldn't normally choose a device with a NRND status if I was designing something from the ground up but seeing as though this is the only chip I have at the moment for experimentation, I thought I would give it a go.

As for using the the other datasheet for the filter coefficients, I was hoping the same filter internals were being used in the IC to save on re-design costs.

Thanks

Miroslav BATEK · ‎2018-02-23

Posted on February 23, 2018 at 13:02

Here are the cut-off frequencies for high pass filter:

Adam Hamilton · ‎2018-02-24

Posted on February 24, 2018 at 23:11

Thanks for taking the time for finding this information Miroslav

Much appreciated

Kind regards

Adam