Recommended Ultra LowPower Accelerometer chip for pedometer app.?

[zarie3]

Hi,

We are working with MMA8451Q in a transient application and it works OK.

We are no looking for a very/ultra low power chip for a Pedometer application.

The question is whether the MMA8451Q can fit into such an application ? are there any instructions how to configure it for that app ? is there a sample code to configure it properly and also have the calc part in the ucontroller to process that data and count steps ?.

Thanks,

Arie

[TomasVaverka]

Hi Arie,

Currently, I am not aware of any implementations of pedometer algorithms using the MMA8451Q accelerometer.

I would highly recommend the MMA9553L - a ColdFire V1 MCU with an accelerometer preloaded with a pedometer application. You can customize and control the behavior of the pedometer application using a few configuration registers and report back the measured and calculated data using several status registers. For more information on this device, please refer to the MMA9553LSWRM.

Regards,

Tomas

PS: If my answer helps to solve your question, please mark it as "Correct". Thank you.

[zarie3]

Tomas Hi,

Thank you for your email and clarifications.

One of the things that I can not fully determine out of the MMA9553L datasheet is the power consumption.

If the power consumption is "Supply current in RUN mode" is 3.1mA this is too much/high for our application, and thus I would appreciate if you can provide an alternate product with lower current consumption.

Regards,

Arie

[JackITB]

Hi Arie,

The 3.1mA is the peak current consumption, i.e. when the MCU is running continuously at full speed. This is not representative of the pedometer consumption which is about 200µA and can be significantly reduced with autonomous suspend mode. The pedometer operating current numbers are actually provided in the MMA9553L Software Release Note document.

To go further in current reduction, the attached presentation describes several optimisation tricks for MMA9553L.

Regards,    Jacques.

[zarie3]

Jacques Hi,

Thank you for your swift reply.

I shall dive more into the pdf details, things seems much better if we are talking on 200uA and be be reduced further significantly.

I roughly read through to the end of the pdf and reached the last bullet of the Optimization Conclusion; my question is: if the walking is not continuous (e.g walk 5 sec, stand 5 sec etc.) how many steps might the pedometer lose in count ? I ask this since we are aiming the pedometer as a cattle application.

Regards,

Arie

[zarie3]

Jacques Hi,

One more question ?

Roughly what should we expect/plan/count for low power consumption ?

BR,

Arie

[JackITB]

Hi Arie,

For the discontinuous walking use case you described, the best trade off in term of step counting accuracy vs current consumption will be is to use the Pedometer auto-suspend feature. The expected consumption assuming a 50/50 ratio (for walk/still activity duration) will be about 100µA.