ranges of values

[tcurdt]

Thanks for the library!

What would be great for the docs to mention the min and max values.
I guess for ADXL345_RANGE_8G it would be -8G/+8G (for example).

The range of the raw values are not quite so obvious.
From the code it looks like 16bit values.

rawVal.x = (static_cast<int16_t>((rawData[1] << 8) | rawData[0])) * 1.0;
corrRawVal.x = rawVal.x * 1.0 - (offsetVal.x / rangeFactor);
gVal.x = corrVal.x * MILLI_G_PER_LSB * rangeFactor * corrFact.x / 1000.0;

So by default it should be which could be calculated backwards per range factor.

rx = (gx * 1000.0 / (MILLI_G_PER_LSB * rangeFactor * corrFactx) + offsetValx) / rangeFactor

Does that make sense?

[wollewald]

Hi @tcurdt ,

the ADXL345 has two different modes, the fixed 10-bit resolution mode and the full resolution mode. In full resolution mode one bit is always 3.9 milli-g (=MILLI_G_PER_LSB). In this mode the range of raw values depends on the range you choose:

2g: 10 bits of the data registers are used, from -2^9 to + 2^9 - 1
4g: 11 bits of the data registers are used, from -2^10 to + 2^10 - 1
8g: 12 bits of the data registers are used, from -2^11 to + 2^11 - 1
16g: 13 bits of the data registers are used, from -2^12 to + 2^12 -1

In the fixed 10-t resolution the range of raw values is 10-bit for all g-ranges. This means that 2^9 -1 in the 2g range equals +2g (1,9929 g, to be exact). In 4g range it is +4g and so on.

With setFullRes(true/false) you can switch between the modes. If true, the rangeFactor is always 1, if false 1, 2, 4 or 8 to consider changing g per bit.

I am not going to write all this into the cpp or h files. I have documented this in the examples of this library and I am explaining this also in my blog posts which are related to this library (see readme).

[tcurdt]

Thanks for the explanation!