Low power GPIOTE beacon

[Avi]

I want to make a low power beacon with GPIOTE input which indicates movement and causing a change in the beacon advertisement (e.g. minor value). In order to do that I am using the gpiote event and initializing the advertisment data, stop and start. Since the GPIOTE resistot can be selected between pullup and no pull, I selected no pull and added expernal resistor of 100Kohm (instead of the internal 10Kohm), in order to save energy (since the tilt switch is always moving and causing gpiote event.

Still the current consumption due to the continouse stop start events is quite bug, I cannpt achieve real low power.

Is there any other way to get low power with tilt switch?

[nRF5xFanboy]

Hi Avi,

Just some questions to get a better understanding of your case?
- What is the current measured you see now?
- What is your expected current?
- Is the tilt switch measuring 1dimentsional or 3D?
- Did you consider to use a 3d accelerometer instead off the tilt switch?

Best regards,
    nRF5xFanBoy

[Avi]

It is 3D tilt switch.

The current during no menment is the minimum (~3uA). When it moves, the current is rising to 13uA (due to 100K resistor), But there is a spike of current which I cannot measure (due to stop/start advertisment process). Overall, it takes too much.

[Avi]

accelerometer requires constant monitoring - so I assume it will take more current since the chip cannot be in sleep mode

[nRF5xFanboy]

Hi Avi,

The modern accelerometer often use multiple interrupt pins 
The modern accelerometer often contain smart functions that require only configuration.
So no constant monitor is needed by the mcu.

Otherwise using low sample rate to detect (pre) motion events and switch to high samples rate of the accelerometer to monitor the real motion. Both events can generate on separate interrupt pin

I also disable/enable the entire chip by attach it vdd pin to a LDO being controlled by a gpio pin when I did not need it.

I use this solution with a nrf52840 and it runs for three years on a single battery.
Overall current average 20-25 uA.(mostly due to bluetooth) upon a limited motions detected per day.
You can adapt the scan/discovery settings of bluetooth to reduce the current consumption.

You can log & measure the current spikes using the nordic power profiles MKII
One of my favorite gadgets.

Best regards,
    nRF5xFanBoy