I2C LIS3DH Sample Temperature #423
Description
Concerning the I2C LIS3DH sample, the way the incidental temperature sensor is handled doesn't seem correct.
On line 50, you're configuring with the query address TEMP_CFG_REG. However, it looks like that address (0xC0) was copy-pasted from the value you're giving it, also 0xC0. According to the datasheet (pg. 31), this is not a valid register[1]. That is quite bad, actually—the datasheet repeatedly warns against writing read-only or reserved registers, citing permanent hardware damage.
Assuming I'm right about all this (I don't yet have the hardware myself), the solution is simple: change the definition of TEMP_CFG_REG to 0x1f, its actual address. [2]
[1] It may have alternately come from confusion with register OUT_ADC3_L at address 0x0C, which is used (along with 0x0D for >8-bit modes) for reading out the temperature (it's used for that purpose correctly below).
[2] Incidentally, while we're looking at the sample, I'd like some more documentation about it too. For example, I assume the scaling by 64 in lis3dh_calc_value(⋯) corrects for the chip's left-aligned data-output (16-bit -> 10-bit). The sensitivity must be found by realizing that the -2 to +2 default gee range is 4 gees over 10-bit (1024 code points), so 0.00390625 ≈ 0.004 gees/codepoint. These calculations are only valid for certain configurations, and they're wholly mysterious without diving into the datasheet.