Ultra-low power IMU for step counting

[brian239955_stm1]

I need to develop a low-power embedded device with pedometer functionality. I'm looking at the LIS3DH because of it's low power, but there's no built-in pedometer application. I've also looked at the LSM6DSL, as it has built-in pedometer support, but the power consumption is ~8x higher. Is there a low-power IMU with built-in support for step counting? Or are these my best options? I'd like to minimize power consumption by the IMU as well as power consumption by the MCU controlling the IMU.

Thanks!

Brian

[Eleon BORLINI]

Hi Brian @brian239955_stm1​ ,

if you are searching for a combination of low current consumption (an accelerometer instead of an IMU) and for embedded step counter, you might consider the LIS2DS12 accelerometer, which current consumption is similar to the LIS3DH one (12 uA at ODR=100Hz LP versus 11uA at ODR = 50Hz NM).

As you can see from the datasheet, p.31, the pedometer generates an interrupt when a step is recognized, the step counter (automatically enabled when step detector is on) counts the number of the steps detected. Step Detector/Step Counter (SD/SC) are enabled by setting to ‘1’-logic the STEP_CNT_ON bit in the FUNC_CTRL (3Fh) register. Additional pedometer advanced configurations can be used if the FUNC_CFG_EN bit in CTRL2 (21h) is set to "1".

Further details about the parameters to be configured and the correspondent registers are available from page 62.

Moreover, a simple configuration for this embedded feature can be found in the application note AN4748, p.29:

1. Write 20h in CTRL1
// Turn on the accelerometer
// ODR = 25 Hz, FS = ±2 g
2. Write 01h in FUNC_CTRL // Enable pedometer algorithm
3. Write 04h in CTRL5 // Step detector interrupt driven to INT2 pin

If my reply answered your question, please click on Select as Best at the bottom of this post. This will help other users with the same issue to find the answer faster. 

-Eleon

[brian239955_stm1]

Thanks for the concise details Eleon - this is exactly the info I needed!

Brian

[jonathonpross]

Hello there,

I'm looking for some more information on how the Pedometer works. Does the device need to be attached to the ankle in order to detect steps? I was looking in the configuration registers on the datasheet that was linked above, but I'm curious about the versatility of this. I've got a client interested in adding step counts to their product and I'd like to find a bit more information about whether or not this could be a turn key solution for that feature.