Hello,
I am working on adding a pedometer to the Sensorwatch project using this chip.
I have the step counter working well, and I also have it working with the LIS2DW. Here's a video of it :)
The LIS2DW works by sending 12.5Hz worth of data from its FIFO every second to the host uC, which runs an algorithm to count the steps.
I am finding with a Nordic Power Profiler that the LIS2DUX uses about 6uA to run the step counter.
The LIS2DW uses nearly 15uA.
But I found that I can heavily lower the battery-draw of the LIS2DW by only reading the FIFO and performing the math only if more than 0.06G is seen, which is seen by an interrupt signal, whic make sthe current draw for 90% of the day to be close to 1uA.
Can anything be done with the LIS2DUX to bring it closer to that efficiency?
The goal of the project is to only need to replace the battery once a year, which means that we'd want no more than an average 2uA draw from the chip.
Questions:
1) What is the most battery-efficient that I can set the step counter to? From the app notes, it seems like the best I can do is 25Hz (ultra low power) since I need at least 25Hz. Below is a link to my setup for the step counter; if you see anything else that could make it better, please let me know!
2) Can I perform the same trick as I did for the LIS2DW of having the chip be in an ultra-low-power mode of 1.6Hz and the step counter turned off, only to turn it on when I see 0.06G? I'm thinking that I can turn the step counter back off if I see no steps for 5 minutes and only turn it back on if I see 0.06G again. Will that cause issues the step counter aside from a few lost steps? The datasheet shows that we'll still use up 3uA at 1.6Hz, can that be brought down any further?
3) I also notice that the LIS2DUX undercounts steps. Are there any variables that can be used to make it more sensitive to seeing steps? I found the debounce values in the app notes and tweaked them, but I'd like to see if there's anything else I can do that may not be mentioned in the datasheet or app notes.
Call to Start the set counter in my code: https://github.com/voloved/second-movement/blob/e91f65fe3e94ce76985accf9089a8d16b31d6423/movement.c#L1182
