Overview
In this article:
One of the key benefits of FlexSense is its ultra-low power design, enabling years of lifetime on two or four AA Lithium batteries. However, verifying that your firmware is behaving as expected and allowing the FlexSense to enter its low-power modes requires measuring current draw directly.
This section guides you through using a Nordic Power Profiler Kit II (PPK2) to observe the actual power profile of your FlexSense firmware and verify that the device enters low-power sleep between jobs.
Required Equipment
- Myriota FlexSense Device (batteries removed)
- Nordic PPK2 (Power Profiler Kit II)
- Micro-USB cable for PPK2
- nRF Connect for Desktop + Power Profiler App (downloaded from within nRF Connect for Desktop)
How to Measure Current Draw
The idea is that the PPK2 provides power to the FlexSense, while measuring the current.
Recommended Part List
We recommend the following parts for probing the battery terminals.
| Description | Manufacturer | Part number |
|---|---|---|
| Clamp-type test probe with 4mm banana plug socket - black | Hirschmann Test & Measurement | 930113100 |
| Clamp-type test probe with 4mm banana plug socket - red | Hirschmann Test & Measurement | 930113101 |
| Test lead with 4mm banana plug to 0.64mm square pin socket- black | Hirschmann Test & Measurement | 934160100 |
| Test lead with 4mm banana plug to 0.64mm square pin socket- red | Hirschmann Test & Measurement | 934160101 |
Wiring Diagram
Below are the steps to connect the FlexSense to the PPK2:
Insert the banana plug from the red test lead into the red banana-plug socket on the clamp probe.
Insert the banana plug from the black test lead into the black banana-plug socket on the clamp probe.
Insert the female square pin from the red test lead into the VOUT terminal on the PPK2.
Insert the female square pin from the black test lead into the GND terminal on the PPK2.
With the FlexSense’s USB-C port facing upward, attach the grip jaws from the red clamp probe to the left battery terminal inside the FlexSense.
With the FlexSense’s USB-C port facing upward, attach the grip jaws from the black clamp probe to the right battery terminal inside the FlexSense.
The following wiring diagram illustrates this connection.
Measuring
- Connect the FlexSense battery terminals to the PPK2.
- Connect the PPK2 to the PC, Launch nRF Connect for Desktop and Open the Power Profiler app.
- Select your PPK2 and set the Power Supply Mode to
Source Meter - Set the source voltage to 3600mV (to emulate L91 lithium cells) and enable the power output.
- Set the sampling to 100,000 samples per second, which is set to sample forever.
- Click Start
Expected Current Profile
| State | Current (typical) | Description | Duration |
|---|---|---|---|
| Soft Off | 1µA - 2 µA | This is the current expected when the FlexSense is powered, but the button has not been pressed for the first time | Until the button is pressed |
| Wake Up and GNSS Fix | 5mA - 2A | The device is executing its boot procedure and acquiring a GNSS fix | 90s to 120s |
| BLE Advertising | 0.5mA - 2mA | The BLE is advertising, and the device can be connected to in the FlexAssist Mobile App | 60s |
| Sleep | less than 10µA | The FlexSense is in Low Power mode | Until next Job |
Troubleshooting High Sleep Current
| Symptom | Likely Cause | Potential Fix |
|---|---|---|
| Sleep current greater than 10 µA | GPIO or peripheral leakage | Confirm that where Init API functions were used, De-Init functions were called before a job is finished. |
| Sleep current greater than 100µA | BLE advertising not switched off | Confirm that no devices are connected to the FlexSense via Bluetooth, as this will keep the BLE on. |
| Sleep current never below 1mA | The Device is not entering Sleep mode | Confirm that there are no loops or functions in your user application that will keep a job from ending and allowing the system to enter Sleep mode. |
