LIS3DH_DATARATE_LOWPOWER_5KHZ mode is not setting the accelerometer in 5kHz low power mode but in 1.344 kHz High resolution mode about adafruit_lis3dh

[nalexopo]

@erichiggins

Some suggestions from my part as I just saw that you replied.

1. Don't use the datasheet from adafruit site but rather the one from ST site because it has been revised a few times from the 2010 version your link leads to. This is the 2016 version you can see some differences in the ODR that's why i am talking about 1.344 kHz and not 1.250 kHz.

Here the December 2016 version which is the current version.
https://www.st.com/resource/en/datasheet/lis3dh.pdf

2. If you are planning on going full speed on this sensor have a look on the application note page 9/59
   you may be limited by bandwidth limitations when using HR mode.

https://www.st.com/content/ccc/resource/technical/document/application_note/77/ed/e7/e1/28/5a/45/d6/CD00290365.pdf/files/CD00290365.pdf/jcr:content/translations/en.CD00290365.pdf

[erichiggins]

I was looking into setting a faster data rate in my sketch and came across this reported issue. I haven't tried implementing it yet, but I wanted to share some additional information from the docs in case it helps anyone to confirm (and/or fix) the issue reported above.

Based on what I've read and the information below, I believe the following code is needed to use low-power (5khz) mode. Please double-check before trying it for yourself.

// Enable all axes, low-power mode
writeRegister8(LIS3DH_REG_CTRL1, 0xf);
// 5khz data rate
setDataRate(LIS3DH_DATARATE_LOWPOWER_5KHZ);
// High res off,  BDU enabled
writeRegister8(LIS3DH_REG_CTRL4, 0x80);

Datasheet info

The following is taken directly from page 9 of the Application Note.

Referring to the LIS3DH datasheet, output data rate (ODR) and low power enable (LPen)
bits of CTRL_REG1 and HR bits of CTRL_REG4 are used to select the operating modes
(power-down mode, normal mode and low power mode) and output data rate (Table 2 and
Table 3).

Table 2. Operating mode selection

Operating mode	CTRL_REG1[3] (LPen bit)	CTRL_REG4[3] (HR bit)	BW [Hz]	Turn-on time [ms]
Low power mode	1	0	ODR/2	1
Normal mode	0	1	ODR/9	7/ODR

Table 3. Data rate configuration

ODR3	ODR2	ODR1	ODR0	Power mode selection
0	0	0	0	Power-down mode
0	0	0	1	Normal/low power mode (1 Hz)
0	0	1	0	Normal/low power mode (10 Hz)
0	0	1	1	Normal/low power mode (25 Hz)
0	1	0	0	Normal/low power mode (50 Hz)
0	1	0	1	Normal/low power mode (100 Hz)
0	1	1	0	Normal/low power mode (200 Hz)
0	1	1	1	Normal/low power mode (400 Hz)
1	0	0	0	Low power mode (1.5 kHz)
1	0	0	1	Normal (1.250 kHz)/low power mode (5 kHz)

I believe these correlate to the these data rate options in Adafruit_LIS3DH.h.

References

• LIS3DH datasheet
• Setting default rate (400hz), normal mode, and high-res in Adafruit_LIS3DH.cpp
• Implementation of setDataRate()

[erichiggins]

@ladyada Is this repo still being maintained? There are several open PRs and Issues, like this one, which have not had responses.

[hakeemta]

HR bit in LIS3DH_REG_CTRL5

HR bit is in LIS3DH_REG_CTRL4