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Exercise 1 – Powering nRF54L devices from a single AA/AAA battery

In this exercise, you will learn how to power an nRF54L SoC from a single 1.5 V AA or AAA battery using the nPM2100 PMIC.

nPM2100 EK to nRF54L15 DK connection diagram

You will first create and export a configuration for the nPM2100 PMIC using the nPM PowerUP app (from nRF Connect for Desktop). Then, you will integrate this configuration into an nRF Connect SDK application.

After that, you will familiarize yourself with some Zephyr Driver APIs to further deepen your understanding of the development process for Nordic’s PMICs.

The application running on the nRF54L SoC will periodically pull information from the PMIC about the battery voltage and the boost regulator output, and advertise it as a Bluetooth LE non-connectable advertisement so that it can be displayed on a smartphone/tablet running nRF Connect for Mobile.

Note

This exercise has limited support for the following SoCs:

nRF54LV10: The SoC is not supported in this exercise as it is a unique SoC in the nRF54L Series with built-in support for 1.2-1.7 V supply for Continuous Glucose Monitoring (CGM) devices.

Special hardware requirements

You will need the following extra hardware to complete this exercise

The nPM2100 EK
An alkaline AA or AAA battery
Six female-female jumper wires

Exercise steps

The starting point is an nRF54L SoC that requires power from a single AA or AAA battery. Since the voltage of an AA/AAA battery is below the nRF54L supply voltage range (1.7 – 3.6 V), you need a boost converter. Adding the nPM2100 PMIC to this design is the ideal choice. In addition to a high-efficiency boost converter, this PMIC also integrates a lot of features useful for system management and user interaction.

In this exercise, you will design an application that includes the system power management. It also has the following features:

A button (SHPHLD) that distinguishes three button push lengths.
The PMIC’s second regulator (LDO/LDSW) in Load Switch mode, with on/off control by a GPIO.

With this setup, you can accept different modes of user interaction with the device through a single button and provide a feedback using, for example, an LED or a haptic motor wired to the LDSW output.

1. Configure the nPM2100 in the nPM PowerUP

1.1 Insert the AAA or AA battery holder add-on board, with the battery installed, into the nPM2100 Evaluation Kit and connect the “nPM Controller” port to your computer with a USB-C cable.

nPM2100 EK battery and USB to host connections

1.2 Open the nRF Connect for Desktop and launch the nPM PowerUP application.

1.3 On the DASHBOARD tab of the application, you can see the battery voltage measurements, as well as the nPM2100 Boost regulator voltage setting, which you can keep at the default level or adjust as desired.

nPM PowerUP – dashboard – battery measurements and Boost settings

1.4 In the nPM PowerUP GUI, configure the following. You can learn more about each configuration option by simply hovering your mouse over them.

1.4.1 In the SYSTEM FEATURES tab, make sure that the Power Off Button function is enabled. This setting instructs the PMIC to enter Ship mode when the SHPHLD button is pressed for longer than two seconds.

1.4.2 In the GPIOS tab, match the GPIO settings with the following screenshot:

GPIO0 – active-high interrupt output – this GPIO will signal PMIC interrupts to the host SoC.
GPIO1 – input with a pull-up – this GPIO will act as a control input for the LDSW regulator allowing the host SoC to enable or disable the regulator without TWI communication.

1.4.3 In the REGULATORS tab, configure the Load Switch regulator.

These options allow the Load Switch regulator to be controlled by the state of the GPIO1 pin configured earlier.

1.5 Test the functionality of the settings.

Hold down the GPIO1 button to enable the Load Switch regulator. Check the Voltage graph in the GRAPH tab for a drop to confirm this (a high load is set by default in header P14 on the nPM2100 EK).

Voltage drop while holding the GPIO1 button

As for the ship mode testing using the SHPHLD button, we will perform this as the last step in this exercise.

2. Export the configuration.

Now that you have configured the PMIC, save the configuration to use it in your nRF Connect SDK project.

2.1 Click the Export Configuration button in the upper left corner of the nPM PowerUP, and navigate to the l2_e1 directory inside the cloned GitHub repository for this course.

2.2 Change the filename to npm2100_pmic.overlay to identify it later.

3. Integrate the PMIC configuration into the project

Now that the PMIC configuration has been completed and exported, you need to do the following steps:

Close the nPM PowerUP application window.
You must disconnect the USB cable from the nPM Controller port on the EK, as the nPM Controller would interfere with the EK to DK communication we will set up in step 5.2

You will now start configuring and building an nRF Connect SDK application. The nRF54L SoC will be powered by and communicate via TWI (I2C-compatible) with the nPM2100 PMIC on the nPM2100 EK.

In the GitHub repository for this course, go to the base code for this exercise, found in l2/l2_e1.

You have your initial PMIC configuration, but you will need to modify it slightly to fit the project’s requirements.

3.1 While the nPM PowerUP has configured everything about your PMIC, you still need to add some settings specific to your SoC.

Edit the pmic_gpios.overlay file to specify the following:

3.1.1 Pin P0.02 is an active-high interrupt input using the DTS property host-int-gpios in the npm2100_pmic node.

host-int-gpios = <&gpio0 2 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>;

Copy

host-int-gpios = <&gpio0 2 (GPIO_ACTIVE_HIGH | GPIO_PULL_DOWN)>;

Devicetree

3.1.2 Pin P0.03 is an active-low LDSW control output using the DTS property dvs-gpios in the npm2100_regulators node.

dvs-gpios = <&gpio0 3 GPIO_ACTIVE_LOW>;

Copy

dvs-gpios = <&gpio0 3 GPIO_ACTIVE_LOW>;

Devicetree

4. Add code to handle PMIC interrupts and display VBAT & VOUT (VDD)

To use the PMIC configuration inside the application, modify the code in the src/main.c file as follows:

4.1 Prepare and add a callback for SHPHLD pin’s rising and falling edges.

Refer to the mfd_npm2100_add_callback function documentation, use enum mfd_npm2100_event (doc) to specify the events to be handled.

4.1.1 Initialize the npm2100 callback.

gpio_init_callback(&shphld_cb, events_handler, BIT(NPM2100_EVENT_SYS_SHIPHOLD_FALL) |
							BIT(NPM2100_EVENT_SYS_SHIPHOLD_RISE));

Copy

gpio_init_callback(&shphld_cb, events_handler, BIT(NPM2100_EVENT_SYS_SHIPHOLD_FALL) |
							BIT(NPM2100_EVENT_SYS_SHIPHOLD_RISE));

4.1.2 Add the npm2100 callback to the mfd driver.

ret = mfd_npm2100_add_callback(npm2100, &shphld_cb);
if (ret < 0) {
    LOG_ERR("failed to add a callback (%d)", ret);
	return ret;
}

Copy

ret = mfd_npm2100_add_callback(npm2100, &shphld_cb);
if (ret < 0) {
    LOG_ERR("failed to add a callback (%d)", ret);
	return ret;
}

4.2 Add battery voltage reading to be periodically included in non-connectable Bluetooth LE advertising.

Refer to the Sensor interface documentation.

4.2.1 Fetch a new measurement.

ret = sensor_sample_fetch(npm2100_adc);
if (ret < 0) {
	LOG_ERR("failed to fetch (%d)", ret);
	return ret;
}

Copy

ret = sensor_sample_fetch(npm2100_adc);
if (ret < 0) {
	LOG_ERR("failed to fetch (%d)", ret);
	return ret;
}

4.2.2 Get the SENSOR_CHAN_GAUGE_VOLTAGE channel result into vbat.

ret = sensor_channel_get(npm2100_adc, SENSOR_CHAN_GAUGE_VOLTAGE, vbat);
if (ret < 0) {
	LOG_ERR("failed to get gauge voltage channel (%d)", ret);
	return ret;
}

Copy

ret = sensor_channel_get(npm2100_adc, SENSOR_CHAN_GAUGE_VOLTAGE, vbat);
if (ret < 0) {
	LOG_ERR("failed to get gauge voltage channel (%d)", ret);
	return ret;
}

4.2.3 Get the SENSOR_CHAN_VOLTAGE channel result into vout.

ret = sensor_channel_get(npm2100_adc, SENSOR_CHAN_VOLTAGE, vout);
if (ret < 0) {
	LOG_ERR("failed to get voltage channel (%d)", ret);
	return ret;
}

Copy

ret = sensor_channel_get(npm2100_adc, SENSOR_CHAN_VOLTAGE, vout);
if (ret < 0) {
	LOG_ERR("failed to get voltage channel (%d)", ret);
	return ret;
}

5. Build and flash the application.

5.1 Build the application

Now that the application is ready, add a build configuration for your board target. In the screenshot below, we are assuming an nRF54L15 DK board.

Make sure you include the npm2100_pmic.overlay&pmic_gpios.overlay as Extra Devicetree overlays as shown in the screenshot below:

Then, click on Generate and build

5.2 Connect the nPM2100 EK to your nRF54L DK (nRF54L15 DK | nRF54LM20 DK | nRF54LS05 DK)

To test your application, connect the DK to the nPM2100 EK as shown in the figure/table below. Make sure to remove the jumper on the “VDD Current Measure” header to allow the nPM2100 to power the nRF54L Series SoC instead of using the DK’s onboard power supply.

Description	nPM2100 EK pin	nRF54L DK ( nRF54L15 DK \| nRF54LM20 DK \| nRF54LS05 DK ) pin
Power	VOUT	“VDD Current Measure” header, nRF54 (middle pin) .
Power	GND	GND
Two-wire interface	SDA	P1.08
Two-wire interface	SCL	P1.09
PMIC interrupt GPIO	GPIO0	P0.02
Load Switch control GPIO	GPIO1	P0.03

This way, the nPM2100 PMIC powers the nRF54L15 SoC, ensuring the correct IO reference for the TWI. The PMIC GPIOs are connected to the SoC GPIOs for interrupt signaling and LDSW control.

5.3 Flash the application to your nRF54L DK

Note

Use a USB-C cable to flash the nRF54L DK with the application.

After flashing, you can remove the USB-C cable from the development kit, and the nRF54L SoC will continue to operate (you will see the Bluetooth LE advertisements in the next step). However, without a USB cable there may be some leakage current to the debugger and other components on some older version DKs.

Flash the application to your DK using the nRF Connect for VS Code extension(ACTIONS-> Flash).

Flashing the application to the development kit

6. Testing using nRF Connect for Mobile

Open nRF Connect for Mobile (Android and iOS) and scan for devices, you should see an advertising Device called L2E1 . The nRF54L SoC is configured to advertise both the battery voltage(VBAT) and VDD voltage powering the SoC as manufacturer-specific data. Both of these readings are obtained from the nPM2100 PMIC.

Important

On nRF Connect for Mobile (Android version), you can change the format of manufacturer-specific data from raw hex to Text (UTF-8) by pressing on the the raw hex data. On iOS, this feature is not supported; the data displays as raw hex only. In that case, manually copy the raw hex data (e.g., using Chrome browser: chrome://bluetooth-internals/#devices, scan for devices, locate the L2E1 device), then use an online tool to convert hex to UTF-8)

The SW controls the following:

Pressing the SHPHLD button shortly will cause the LDSW to output a single 0.5 s pulse.
Pressing and holding the SHPHLD button for at least 0.5 s will produce two pulses, each 0.25 s in duration (4 Hz).
The HW is configured to “power off” (PMIC enters the Ship mode), when the SHPHLD button is held for longer than two seconds. This will unpower the nRF54L15 DK as well, so no further advertisement is seen in the nRF Connect for Mobile. To power the system back on, hold the button again for longer than two seconds.

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Designing Low-Power Bluetooth LE Products

Exercise 1 – Powering nRF54L devices from a single AA/AAA battery

Note

Special hardware requirements

Exercise steps

Note

Important

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MCUboot & Partition Manager