XIAO nRF54L15 功耗示例 (PlatformIO)
以下示例代码专为 PlatformIO 设计，但也与 nRF Connect SDK 兼容。
tip
基于 VS Code，如果您想在 nRF Connect SDK 上使用以下案例，请参考提供的连接，添加 app.overlay 文件并修改 prj.conf 中的内容
蓝牙连接
本节详细介绍了设备作为蓝牙低功耗 (BLE) 外设主动广播时的功耗特性。设备实现了自定义 BLE 服务，允许其他中心设备连接并与其交互。
以下图表展示了设备持续广播时的典型功耗配置文件：
BLE 广播期间的设备功耗
如图所示，设备表现出与每个广播事件相对应的周期性电流峰值，随后是较低电流消耗的时期。广播期间的平均功耗高于系统关闭模式，反映了广播所需的主动无线电操作。
BLE 广播代码示例
以下是用于测试 BLE 广播期间功耗的代码：
#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;
}
超低功耗状态
为了实现设备的极低功耗，我们在 System Off 模式下进行了功耗测试。System Off 模式是 Zephyr 操作系统提供的深度睡眠模式，在此模式下大部分外设和 CPU 都会关闭，仅保留必要的唤醒源（如 GPIO 中断）以最小化功耗。
以下图表展示了设备进入 System Off 模式后的典型功耗曲线：
设备在 System Off 模式下的功耗
如图所示，进入 System Off 模式后，功耗显著降低，仅维持在微安级别，这大大延长了电池寿命。当按下 sw0 按钮时，设备将从 System Off 模式唤醒并重新启动。
功耗代码示例
以下是用于测试上述 System Off 模式功耗的代码：
/*
* 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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