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Getting Started with Seeed Studio XIAO nRF54LM20A Sense

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Introduction​

Seeed Studio XIAO nRF54LM20A Sense is a compact, ultra-low-power wireless development board built around Nordic Semiconductor’s nRF54LM20A SoC. It combines a 128 MHz Arm Cortex-M33 processor, 512 KB RAM, 2 MB on-chip NVM, multiprotocol 2.4 GHz wireless connectivity, onboard IMU, digital microphone, 8MB external flash, IPEX antenna connector, and nPM1300 PMIC for advanced battery-powered IoT, wearable, smart sensing, and edge AI applications.

Specification​

Product NameSeeed Studio XIAO nRF54LM20ASeeed Studio XIAO nRF54LM20A Sense
ProcessorArm® Cortex®-M33 128 MHz & RISC-V 128 MHz Coprocessor
RAM512KB
Flash2 MB Non-volatile Memory (NVM)
External Flash8MB onboard external flash
PMIC / BatterynPM1300 PMIC for power regulation and battery charging
Interface

28x GPIO Pin
9x Analog Pin
1x I2C
1x UART
1x SPI
1x NFC
1x SHPHLD

Onboard

1x User LED (R/G/B 3 Color)
1x Charge LED (Battery Charging Indicator)
1x Reset Button
1x User Button
1x IPEX4 Connector (for external antenna)

1x User LED (R/G/B 3 Color)
1x Charge LED (Battery Charging Indicator)
1x Reset Button
1x User Button
1x IPEX4 Connector (for external antenna)
1x 6-Axis IMU
1x PDM Microphone

Wireless Connectivity

Bluetooth LE 6.0 (include Channel Sounding)
Bluetooth Mesh
NFC
Thread
Zigbee
Matter
Amazon Sidewalk
Proprietary 2.4 GHz protocols

Power Input

Type-C: 5V
Battery: 3.7V

Low Power Mode (3.7V@2A)/

Light-Sleep: ~9.96µA
Deep-Sleep (System OFF): ~4.76µA
Deep-Sleep (System OFF, GRTC wake-up): ~4.92µA
Ship-Mode: 0.33µA

Software Compatibility

Nordic nRF Connect SDK (based on Zephyr RTOS)
PlatformIO (based on Zephyr RTOS)

Working Temperature-20°C to 70°C
Dimensions21 x 17.8mm

Features​

  • Powerful SoC with Advanced Connectivity & Security

    Seeed Studio XIAO nRF54LM20A Sense is a compact, ultra-low-power wireless development board powered by Nordic Semiconductor’s nRF54LM20A SoC. It features a 128 MHz Arm Cortex-M33 processor, 512 KB RAM, 2 MB on-chip NVM, a 128 MHz RISC-V coprocessor, multiprotocol 2.4 GHz wireless connectivity, onboard IMU, digital microphone, 8MB external flash, IPEX antenna connector, and Nordic nPM1300 PMIC for efficient power management.With support for Bluetooth LE, Bluetooth Channel Sounding, Bluetooth Mesh, Thread, Zigbee, Matter, and proprietary 2.4 GHz protocols up to 4 Mbps, this board is built for next-generation connected products. The onboard motion and audio sensors make it ideal for wearables, smart sensing, TinyML, gesture recognition, voice-triggered devices, and battery-powered IoT applications.

  • Ultra-Low Power Efficiency

    Built on Nordic nRF54LM20A and nPM1300 PMIC, XIAO nRF54LM20A Sense achieves a measured deep sleep current of only 4.76 µA under BAT power. Combined with the nPM1300 PMIC and its 0.33 µA Ship Mode BAT current, in active wireless operation, it records an average current of 3.87 mA with a 3.7 V simulated battery input and TX power set to +8 dBm, the board is ideal for long-life battery-powered sensing applications, wearables, and always-on IoT devices.

  • Streamlined Development Experience

    Full support for Nordic nRF Connect SDK and PlatformIO (Zephyr) enables efficient embedded development workflows. (Note: Arduino IDE is currently not supported)

Hardware Overview​

XIAO nRF54LM20A Front​

XIAO nRF54LM20A Back​

Pin Map​

XIAO PinFunctionChip PinDescription
Power Pins
VBUSVBUS-5V Power Input/Output
GNDGND-Ground
3V33V3-OUT-3.3V Power Output
BAT+BAT+-Battery Input (monitored by nPM1300 via I²C)
BAT-BAT--Battery Negative Terminal
SHPHLDSHPHLD-PMIC Ship/Hibernate Mode Control (ultra-low-power shipping state)
System & Control Pins
RESETRESET-Board Reset
SWCLKSWCLKnRF54LM20A SWCLK / SAMD11 SWCLKSerial Wire Clock (for nRF54 and SAMD11)
SWDIOSWDIOnRF54LM20A SWDIO / SAMD11 SWDIOSerial Wire Data (for nRF54 and SAMD11)
SAMD11_RESETRESETSAMD11 RESETSAMD11 Co-processor Reset
User & LED Pins
-USER_BUTTONP0.09User Button Input
-RGB-BP1.23Onboard RGB LED Blue Channel
-RGB-GP1.24Onboard RGB LED Green Channel
-RGB-RP1.22Onboard RGB LED Red Channel
Analog Input (ADC) Pins
A0AIN0P1.00Analog Input 0 / GPIO
A1AIN1P1.31Analog Input 1 / GPIO
A2AIN2P1.30Analog Input 2 / GPIO
A3AIN3P1.29Analog Input 3 / GPIO
A7AIN7P1.03Analog Input 7 / GPIO
I2C Pins
SDAI2C_SDAP1.03I2C Data Line (IMU & Peripheral)
SCLI2C_SCLP1.07I2C Clock Line (IMU & Peripheral)
-BAT_SDAP1.18Battery Monitor I2C SDA (nPM1300)
-BAT_SCLP1.17Battery Monitor I2C SCL (nPM1300)
UART Pins
TXUART_TXP1.08UART Transmit
RXUART_RXP1.09UART Receive
SPI Pins
MOSISPI_MOSIP1.06SPI Master Out Slave In
MISOSPI_MISOP1.05SPI Master In Slave Out
SCKSPI_SCKP1.04SPI Serial Clock
Onboard Peripheral Pins
-MIC_DATP1.14Microphone Data Line
-MIC_CLKP1.13Microphone Clock Line
-IMU_SDAP0.08IMU I2C SDA (Onboard IMU)
-IMU_SCLP0.07IMU I2C SCL (Onboard IMU)
-IMU_CSP3.12IMU Chip Select
-IMU_INT1P0.06IMU Interrupt 1
-NFCP1.02 / P1.01NFC Antenna Pins
-GRTCP0.04 / P0.05General Purpose RTC Pins

Getting Started With PlatformIO​

In this section, we will guide you to quickly get started with the XIAO nRF54LM20A through the multi-color blinking effect of an RGB LED. Please complete the hardware and software preparations below to set up your XIAO for subsequent development.

Hardware Preperation​

You need to prepare the following:

Seeed Studio XIAO nRF54LM20A Sense

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Download VS Code​

Download according to the system you are using VS Code

Install the PlatformIO extension​

Open VSCode, click on Extensions, then search for PlatformIO and select to install. After the installation is complete, restart VSCode.

Install the platform-seeedboards platform package​

The Seeed Studio XIAO series boards use a custom PlatformIO platform, so you need to install the corresponding platform package manually.

  • Run the following command for a fresh installation:
pio pkg install -g -p "https://github.com/Seeed-Studio/platform-seeedboards.git"

  • If you have previously used Seeed Studio XIAO series boards in PlatformIO, run the command below to update:
pio pkg update -g -p "https://github.com/Seeed-Studio/platform-seeedboards.git"

tip

If you want to use an existing PlatformIO project, replace the content of platformio.ini as follows:

[env:seeed-xiao-nrf54lm20a]
platform = https://github.com/Seeed-Studio/platform-seeedboards.git
framework = zephyr
board = seeed-xiao-nrf54lm20a

Create New Project​

  1. Open the PlatformIO extension and select Create New Project.

  1. Set the project name, select the development board, framework and file storage path.

  1. After creation completes, a prompt to open the workspace will pop up. Click OK.

  1. Navigate to the project folder. Files are stored in the default directory if you did not specify a custom path.
  • For Windows Default:
<path>: C:\Users\your_name\Documents\PlatformIO\Projects
  • For Mac / Linux Default:
<path>: ~/Documents/PlatformIO/Projects

This tutorial is developed based on Zephyr RTOS. The project consists of three core files:

  • main.c: Main program that contains the application logic.
  • app.overlay: Devicetree overlay file for hardware peripheral configuration.
  • prj.conf: Project configuration file to enable required Zephyr modules.
  1. Add the main.c program
main.c

/*
 * Copyright (c) 2016 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/drivers/pwm.h>
#include <nrfx_power.h>

#define PWM_PERIOD_NS 1000000U
#define STEP_TIME_MS 500

#define LED_R_NODE DT_ALIAS(pwm_led1)
#define LED_G_NODE DT_ALIAS(pwm_led2)
#define LED_B_NODE DT_ALIAS(pwm_led0)

#if !DT_NODE_EXISTS(LED_R_NODE) || !DT_NODE_EXISTS(LED_G_NODE) || !DT_NODE_EXISTS(LED_B_NODE)
#error "This RGB blink demo expects pwm-led0/pwm-led1/pwm-led2 devicetree aliases"
#endif

static const struct pwm_dt_spec led_r = PWM_DT_SPEC_GET(LED_R_NODE);
static const struct pwm_dt_spec led_g = PWM_DT_SPEC_GET(LED_G_NODE);
static const struct pwm_dt_spec led_b = PWM_DT_SPEC_GET(LED_B_NODE);

struct rgb_step {
	uint8_t r;
	uint8_t g;
	uint8_t b;
	uint32_t delay_ms;
};

static int pwm_set_u8(const struct pwm_dt_spec *led, uint8_t level)
{
	uint32_t duty_ns = (PWM_PERIOD_NS * (uint32_t)level) / 255U;

	return pwm_set_dt(led, PWM_PERIOD_NS, duty_ns);
}

static int rgb_set(uint8_t r, uint8_t g, uint8_t b)
{
	int ret;

	ret = pwm_set_u8(&led_r, r);
	if (ret < 0) {
		return ret;
	}

	ret = pwm_set_u8(&led_g, g);
	if (ret < 0) {
		return ret;
	}

	ret = pwm_set_u8(&led_b, b);
	if (ret < 0) {
		return ret;
	}

	return 0;
}

int main(void)
{
	int ret;

#if defined(CONFIG_NRFX_POWER)
	nrfx_power_constlat_mode_request();
#endif

	if (!device_is_ready(led_r.dev) || !device_is_ready(led_g.dev) || !device_is_ready(led_b.dev)) {
		return -1;
	}

	static const struct rgb_step demo[] = {
		{ 255, 0, 0, STEP_TIME_MS },
		{ 0, 255, 0, STEP_TIME_MS },
		{ 0, 0, 255, STEP_TIME_MS },
		{ 255, 255, 0, STEP_TIME_MS },
		{ 0, 255, 255, STEP_TIME_MS },
		{ 255, 0, 255, STEP_TIME_MS },
		{ 255, 255, 255, STEP_TIME_MS },
		{ 0, 0, 0, STEP_TIME_MS },
	};

	while (1) {
		for (size_t i = 0; i < ARRAY_SIZE(demo); i++) {
			ret = rgb_set(demo[i].r, demo[i].g, demo[i].b);
			if (ret < 0) {
				return ret;
			}
			k_msleep(demo[i].delay_ms);
		}
	}

	return 0;
}
  1. Add the app.overlay file

The devicetree overlay file does not exist in the newly created blank sample. You need to add it under the zephyr directory.

app.overlay
/*
 * Device tree overlay for XIAO nRF54LM20A RGB LED PWM demo.
 *
 * PWM20 peripheral is used for RGB LED control:
 *   - Channel 0: P1.22 (Blue LED)  -> pwm_led0
 *   - Channel 1: P1.23 (Red LED)   -> pwm_led1
 *   - Channel 2: P1.24 (Green LED) -> pwm_led2
 */

&pwm20 {
	status = "okay";
};

/ {
	pwmleds {
		compatible = "pwm-leds";

		pwm_led0: pwm_led_0 {
			pwms = <&pwm20 0 PWM_MSEC(20) PWM_POLARITY_NORMAL>;
			label = "Blue LED";
		};

		pwm_led1: pwm_led_1 {
			pwms = <&pwm20 1 PWM_MSEC(20) PWM_POLARITY_NORMAL>;
			label = "Red LED";
		};

		pwm_led2: pwm_led_2 {
			pwms = <&pwm20 2 PWM_MSEC(20) PWM_POLARITY_NORMAL>;
			label = "Green LED";
		};
	};
};

/ {
	aliases {
		pwm-led0 = &pwm_led0;
		pwm-led1 = &pwm_led1;
		pwm-led2 = &pwm_led2;
	};
};
  1. Modify prj.conf and enable the corresponding configurations.
CONFIG_GPIO=y
CONFIG_PWM=y
CONFIG_SERIAL=n

Compile and upload the program​

Two methods for compilation and uploading are introduced below.

  1. Compile & Upload via Button

  1. Compile & Upload via Command Line
pio run -e seeed-xiao-nrf54lm20a -t upload -v

Observe the Result​

Bluetooth Antenna​

This board uses an external Bluetooth antenna. To ensure a better quality of Bluetooth signal and enhance your Bluetooth usage experience, it is recommended to install a Bluetooth antenna. The connection method is shown below:

Bluetooth antenna connection

Battery Usage​

The XIAO nRF54LM20A is capable of using a 3.7V lithium battery as the power supply input. You can refer to the following diagram for the wiring method.

Battery wiring
caution

Please be careful not to short-circuit the positive and negative terminals and burn the battery and equipment when soldering. If the battery has power, never solder it onto the board, as this may burn out the circuit board. Short-circuiting while the circuit is powered on poses a significant risk; it is recommended to use an adapter.

Instructions on the use of batteries:

  1. Please use qualified batteries that meet the specifications.
  2. XIAO can be connected to your computer device via data cable while using the battery, rest assured that XIAO has a built-in circuit protection chip, which is safe.

Battery Voltage Detection​

The XIAO nRF54LM20A integrates a battery voltage detection feature that centers on efficiently managing battery power measurements using the nPM1300-CAA load switch. This guide will focus on analyzing the software implementation of the battery detection (especially the main.c code) and guide you on how to easily deploy and use this feature in a PlatformIO environment, avoiding the complexity of the Zephyr NCS SDK.

XIAO nRF54L15 BLE Advertising Power Consumption

Detecting Battery Schematic

What the nPM1300-CAA chip does:

nPM1300-CAA is a highly integrated power management IC (PMIC) that replaces the simple load switch function of the TPS22916. It not only controls battery voltage switching for low-power monitoring but also integrates charging, regulation, and precise fuel gauging (via voltage, current, temperature) to maximize battery life for the nRF54LM20A.

Download the Library

note

The following example works for both PlatformIO and nRF Connect SDK. It can be used directly in PlatformIO, while the SDK requires manually adding files. Refer to this link

Peripherals Overview​

The peripheral circuitry on this board includes an IMU and a microphone. You can see their locations in the diagram below:

IMU and microphone locations

IMU​

The XIAO nRF54LM20A Sense features an LSM6DS3TR-C IMU with a 3-axis accelerometer and a 3-axis gyroscope.

MIC​

The XIAO nRF54LM20A Sense is equipped with an MSM261DGT006 digital microphone for audio capture.

FAQ​

  1. Build errors after modifying configuration files

If you previously built the full Zephyr project and later modified configuration files, it is recommended to clean the build cache before rebuilding and uploading. This helps avoid compilation errors caused by stale or corrupted cache files.

pio run -t clean  // Clean command
  1. zsh: command not found: openocd after installation

When directly entering "openocd" in the terminal, the shell will only search in the directories within the PATH; if the directory has not been added yet, it will prompt that the command cannot be found. Simply add it permanently to ~/.zshrc, following the instructions below. This solution is for macOS users only

echo 'export PATH="$HOME/Library/Application Support/Seeed/OpenOCD/tool-openocd/bin:$PATH"' >> ~/.zshrc
source ~/.zshrc
openocd --version
  1. What should I do if I previously downloaded Seeed Studio XIAO series boards multiple times and now the drop-down of the Platform project fails?

It is recommended to clean up before trying again. Accumulated duplicate and outdated Seeed platform folders under PlatformIO local packages cause overlong file lookup paths and version conflicts, resulting in project loading failure. Clean up redundant mixed-source Seeed platform directories according to the steps below, and only retain the official platform automatically pulled by PlatformIO to avoid conflicts caused by old and incorrect directories: Delete all folders starting with platform-seeed- and framework-seeed-

rm -rf ~/.platformio/packages/platform-seeed-* ~/.platformio/packages/framework-seeed-*

Resources​

Seeed Studio XIAO nRF54LM20A​

Hardware Design

Seeed Studio XIAO nRF54LM20A Sense​

Hardware Design

Tech Support & Product Discussion​

Thank you for choosing our products! We are here to provide you with different support to ensure that your experience with our products is as smooth as possible. We offer several communication channels to cater to different preferences and needs.

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