Power Consumptions Example for XIAO nRF54L15 (PlatformIO)
The following sample code is designed for PlatformIO, but it is also compatible with the nRF Connect SDK.
Based on VS Code, if you want to use the following case on the nRF Connect SDK, please refer to the provided connection, add the app.overlay file and modify the contents in prj.conf
Bluetooth Connected
This section details the power consumption characteristics of the device while it is actively advertising as a Bluetooth Low Energy (BLE) peripheral. The device implements a custom BLE service, allowing other central devices to connect and interact with it.
The following graph illustrates the typical power consumption profile when the device is continuously advertising:
Device Power Consumption during BLE Advertising
As shown in the graph, the device exhibits periodic current peaks corresponding to each advertising event, followed by periods of lower current consumption. The average power consumption during advertising is higher than in System Off mode, reflecting the active radio operations required for broadcasting.
BLE Advertising Code Example
Below is the code used to test the power consumption during BLE advertising:
#include <stdio.h>
#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/hci.h>
#include <zephyr/bluetooth/conn.h>
#include <zephyr/bluetooth/uuid.h>
#include <zephyr/bluetooth/gatt.h>
// Custom 128-bit UUID for the ONOFF Service
#define BT_UUID_ONOFF_VAL BT_UUID_128_ENCODE(0x8e7f1a23, 0x4b2c, 0x11ee, 0xbe56, 0x0242ac120002)
#define BT_UUID_ONOFF BT_UUID_DECLARE_128(BT_UUID_ONOFF_VAL)
// Custom 128-bit UUID for the ONOFF Action Characteristic (Write)
#define BT_UUID_ONOFF_ACTION_VAL \
BT_UUID_128_ENCODE(0x8e7f1a24, 0x4b2c, 0x11ee, 0xbe56, 0x0242ac120002)
#define BT_UUID_ONOFF_ACTION BT_UUID_DECLARE_128(BT_UUID_ONOFF_ACTION_VAL)
// Custom 128-bit UUID for the ONOFF Read Characteristic (Read)
#define BT_UUID_ONOFF_READ_VAL \
BT_UUID_128_ENCODE(0x8e7f1a25, 0x4b2c, 0x11ee, 0xbe56, 0x0242ac120003)
#define BT_UUID_ONOFF_READ BT_UUID_DECLARE_128(BT_UUID_ONOFF_READ_VAL)
// Static flag to hold the on/off state, initialized to 0 (off)
static uint8_t onoff_flag = 0;
// Advertising data: flags and complete device name
static const struct bt_data ad[] = {
BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)), // General Discoverable, No BR/EDR
BT_DATA(BT_DATA_NAME_COMPLETE, CONFIG_BT_DEVICE_NAME, sizeof(CONFIG_BT_DEVICE_NAME) - 1), // Device Name
};
// Scan response data: include the 128-bit UUID of our custom service
static const struct bt_data sd[] = {
BT_DATA_BYTES(BT_DATA_UUID128_ALL, BT_UUID_ONOFF_VAL), // Service UUID
};
/**
* @brief GATT read callback for the ONOFF Read characteristic.
*
* This function is called when a connected central device attempts to read
* the ONOFF Read characteristic. It returns the current value of onoff_flag.
*
* @param conn Pointer to the connection object.
* @param attr Pointer to the GATT attribute being read.
* @param buf Buffer to store the read value.
* @param len Maximum length of the buffer.
* @param offset Offset from which to read the attribute value.
* @return Number of bytes read, or a negative error code.
*/
static ssize_t read_onoff_val(struct bt_conn *conn, const struct bt_gatt_attr *attr,
void *buf, uint16_t len, uint16_t offset)
{
// The user_data field of the attribute points to onoff_flag
const uint8_t *value = attr->user_data;
// Perform the GATT attribute read operation
return bt_gatt_attr_read(conn, attr, buf, len, offset, value, sizeof(*value));
}
/**
* @brief GATT write callback for the ONOFF Action characteristic.
*
* This function is called when a connected central device attempts to write
* to the ONOFF Action characteristic. It updates the onoff_flag based on
* the received value.
*
* @param conn Pointer to the connection object.
* @param attr Pointer to the GATT attribute being written.
* @param buf Buffer containing the value to be written.
* @param len Length of the value in the buffer.
* @param offset Offset at which to write the attribute value.
* @param flags Flags for the write operation.
* @return Number of bytes written, or a negative error code.
*/
static ssize_t write_onoff_val(struct bt_conn *conn, const struct bt_gatt_attr *attr,
const void *buf, uint16_t len, uint16_t offset, uint8_t flags)
{
uint8_t val;
// Ensure the length of the written data is 1 byte
if (len != 1U) {
return BT_GATT_ERR(BT_ATT_ERR_INVALID_ATTRIBUTE_LEN);
}
// Ensure the write operation starts from offset 0
if (offset != 0) {
return BT_GATT_ERR(BT_ATT_ERR_INVALID_OFFSET);
}
// Get the value from the buffer
val = *((uint8_t *)buf);
// Update onoff_flag based on the received value
if (val == 0x00U) {
printf("Write: 0\n");
onoff_flag = 0; // Set to off
} else if (val == 0x01U) {
printf("Write: 1\n");
onoff_flag = 1; // Set to on
} else {
// Return error if value is not 0 or 1
return BT_GATT_ERR(BT_ATT_ERR_VALUE_NOT_ALLOWED);
}
return len; // Return number of bytes successfully written
}
// Define the custom GATT service and its characteristics
BT_GATT_SERVICE_DEFINE(lbs_svc,
BT_GATT_PRIMARY_SERVICE(BT_UUID_ONOFF), // Primary Service: ONOFF Service
BT_GATT_CHARACTERISTIC(BT_UUID_ONOFF_ACTION, BT_GATT_CHRC_WRITE, // Characteristic: ONOFF Action (Write)
BT_GATT_PERM_WRITE, NULL, write_onoff_val, NULL), // Permissions, callbacks
BT_GATT_CHARACTERISTIC(BT_UUID_ONOFF_READ, BT_GATT_CHRC_READ, // Characteristic: ONOFF Read (Read)
BT_GATT_PERM_READ, read_onoff_val, NULL, &onoff_flag), // Permissions, callbacks, user_data (onoff_flag)
);
/**
* @brief Callback function for successful Bluetooth connection.
*
* @param conn Pointer to the connection object.
* @param err Error code (0 if successful).
*/
static void connected(struct bt_conn *conn, uint8_t err)
{
if (err != 0U) {
printf("Connection failed (%02x, %s)\n", err, bt_hci_err_to_str(err));
return;
}
printf("Connected\n");
}
/**
* @brief Callback function for Bluetooth disconnection.
*
* @param conn Pointer to the connection object.
* @param reason Reason for disconnection.
*/
static void disconnected(struct bt_conn *conn, uint8_t reason)
{
printf("Disconnected (%02x, %s)\n", reason, bt_hci_err_to_str(reason));
}
// Define connection callbacks
BT_CONN_CB_DEFINE(conn_callbacks) = {
.connected = connected,
.disconnected = disconnected,
};
/**
* @brief Main function of the application.
*
* Initializes the Bluetooth stack, starts advertising, and enters the main loop.
* @return 0 on success, negative error code on failure.
*/
int main(void)
{
int err;
// Enable the Bluetooth stack
err = bt_enable(NULL);
if (err < 0) {
printf("Bluetooth enable failed (err %d)", err);
return err;
}
// Start BLE advertising
err = bt_le_adv_start(BT_LE_ADV_CONN_FAST_1, ad, ARRAY_SIZE(ad), sd, ARRAY_SIZE(sd));
if (err < 0) {
printf("Advertising failed to start (err %d)", err);
return err;
}
printf("Bluetooth enabled");
return 0;
}
Ultra-low Power State
To achieve extremely low power consumption for the device, we conducted power consumption tests in System Off mode. System Off mode is a deep sleep mode provided by Zephyr OS, where most peripherals and the CPU are turned off, retaining only essential wake-up sources (such as GPIO interrupts) to minimize power consumption.
The following graph illustrates the typical power consumption curve after the device enters System Off mode:
Device Power Consumption in System Off Mode
As shown in the graph, after entering System Off mode, the power consumption is significantly reduced, maintaining only microampere levels, which greatly extends battery life. When the sw0 button is pressed, the device will wake up from System Off mode and restart.
Power Consumption Code Example
Below is the code used to test the power consumption in the System Off mode described above:
/*
* Copyright (c) 2019 Nordic Semiconductor ASA
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <inttypes.h>
#include <stdio.h>
#include <zephyr/device.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/drivers/hwinfo.h>
#include <zephyr/drivers/comparator.h>
#include <zephyr/kernel.h>
#include <zephyr/pm/device.h>
#include <zephyr/sys/poweroff.h>
#include <zephyr/sys/util.h>
static const struct gpio_dt_spec sw0 = GPIO_DT_SPEC_GET(DT_ALIAS(sw0), gpios);
void print_reset_cause(void)
{
uint32_t reset_cause;
hwinfo_get_reset_cause(&reset_cause);
if (reset_cause & RESET_DEBUG) {
printf("Reset by debugger.\n");
} else if (reset_cause & RESET_CLOCK) {
printf("Wakeup from System OFF by GRTC.\n");
} else {
printf("Other wake up cause 0x%08X.\n", reset_cause);
}
}
int main(void)
{
int rc;
const struct device *const cons = DEVICE_DT_GET(DT_CHOSEN(zephyr_console));
if (!device_is_ready(cons)) {
printf("%s: device not ready.\n", cons->name);
return 0;
}
printf("\n%s system off demo\n", CONFIG_BOARD);
print_reset_cause();
/* configure sw0 as input, interrupt as level active to allow wake-up */
rc = gpio_pin_configure_dt(&sw0, GPIO_INPUT);
if (rc < 0) {
printf("Could not configure sw0 GPIO (%d)\n", rc);
return 0;
}
rc = gpio_pin_interrupt_configure_dt(&sw0, GPIO_INT_LEVEL_LOW);
if (rc < 0) {
printf("Could not configure sw0 GPIO interrupt (%d)\n", rc);
return 0;
}
printf("Entering system off; press sw0 to restart\n");
rc = pm_device_action_run(cons, PM_DEVICE_ACTION_SUSPEND);
if (rc < 0) {
printf("Could not suspend console (%d)\n", rc);
return 0;
}
hwinfo_clear_reset_cause();
sys_poweroff();
return 0;
}
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