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

[nalexopo]

lis.setDataRate(LIS3DH_DATARATE_LOWPOWER_5KHZ);

Above code is not setting the accelerometer in 5kHz mode but in 1.344 kHz High resolution mode. I read the LIS3DH_REG_CTRL1 register and i get a value b'1001 0111. It should be b'1001 1111 for 5kHz low power mode and the HR bit in LIS3DH_REG_CTRL4 should be 0. Read Lis3dh datasheet in page 35/54.

[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.

[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

[hakeemta]

HR bit in LIS3DH_REG_CTRL5

HR bit is in LIS3DH_REG_CTRL4

[T-Mosher]

Note, same issue raised via this forum thread:
https://forums.adafruit.com/viewtopic.php?t=211362

Is this issue pending a resolution, stuck, or merely forgotten?

[tyeth]

Hardware arriving on Wednesday, so I'll have a look + test then

[tyeth]

Hey @nalexopo @erichiggins @hakeemta @T-Mosher, there is a PR in to add the functionality, see #50 , it would be really appreciated if you folks could give it a thorough testing!

There is a new constructor argument (frequency - last arg for SPI overloads, defaulting to 500kHz) to allow raising the SPI frequency as needed for the 5KHz rate. I went up to 2MHz.
There is a new method for setPerformanceMode to allow selecting low power / normal / high resolution modes

[T-Mosher]

Sorry, can't test it, don't have the hardware.

[tyeth]

@nalexopo @erichiggins @hakeemta final testing reminder prod ☝️ before I merge it tomorrow and release anyway. We can always fix it afterwards.

[erichiggins]

I'm currently traveling and unable to test this

[tyeth]

Thanks for the thought, and happy travels!

…

On Mon, 8 Jul 2024, 12:56 Eric Higgins, ***@***.***> wrote: I'm currently traveling and unable to test this — Reply to this email directly, view it on GitHub <#14 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABTBZ44JKXWDH53B6SSR3RTZLJ46BAVCNFSM6AAAAABJEZN6TKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDEMJTHAYTCNZTGE> . You are receiving this because you were assigned.Message ID: ***@***.***>

[tyeth]

Please feel free to reopen or create a new issue if there are any problems with the release (1.3.0).