shell - 如何在运行 Linux 的 Dragonboard 410c 上切换 LED 板载

Question

Dragonboard 410c 上有 4 个绿色小 LED，右侧的一个心跳一直在闪烁，如何通过命令行切换其他的。

Answer 1

首先要注意的是，当前正在使用4 个 LED 中的 3 个，但 LED_4 未使用，可以通过命令行打开

// turn on
echo 1 > /sys/class/leds/apq8016-sbc\:green\:user4/brightness

// turn off
echo 0 > /sys/class/leds/apq8016-sbc\:green\:user4/brightness

Answer 2

首先要注意的是，如何访问位于两个 USB 连接器之间的板载 LED 或用户 LED 以及可用的数量取决于您使用的操作系统，Android 或 Linux。

对于 Android 和 Linux，用户 LED 都列在文件夹中，/sys/class/leds因此您可以使用该adb实用程序进行远程访问，然后ls使用该文件夹查看实际的伪文件名是什么。

对于这两者，您将更改brightness位于用户 LED 的伪文件夹中的伪文件中的值，以打开 LED，值为 1 或关闭，值为 0。

还有其他与每个 LED 相关的伪文件，其中一个trigger允许您设置内核事件以触发 LED。在 Raspberry Pi StackExchange 中查看如何使用我的软件控制系统 LED？.

在 Android 下，查看其中几个trigger伪目录的几个伪文件会/sys/class/leds给出以下伪目录的输出boot（用户 LED 4 用于 Android 的启动指示灯），led1（用户 LED 1 可用于 Android 但不适用于 Linux ) 和wlann(LAN 活动指示灯)。

root@msm8916_64:/sys/class/leds # cat boot/trigger
none bkl-trigger [boot-indication] usb-online mmc0 mmc1 battery-charging-or-full battery-charging battery-full battery-charging-blink-full-solid wlan-indication-led
root@msm8916_64:/sys/class/leds # cat led1/trigger
[none] bkl-trigger boot-indication usb-online mmc0 mmc1 battery-charging-or-full battery-charging battery-full battery-charging-blink-full-solid wlan-indication-led
root@msm8916_64:/sys/class/leds # cat wlan/trigger
none bkl-trigger boot-indication usb-online mmc0 mmc1 battery-charging-or-full battery-charging battery-full battery-charging-blink-full-solid [wlan-indication-led]

注意：为了对伪文件使用文件 I/O，文件权限必须允许您要使用的访问类型（读、写、读/写）。LED 伪文件的默认值似乎已被读取，因此该chmod命令需要像sudo chmod 777 /sys/class/leds/led1/brightness.

https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/guides/led-connectors.md.html

位于 USB 端口旁边的是一系列用于向用户提供信息的 LED。它们的用法定义如下：

Debian 映像

安装基于 Debian 的映像时，下表定义了 LED 使用/行为。

+----------------------+----------------------+--------------------------+
| LED Board Identifier | Description          | Behavior                 |
+----------------------+----------------------+--------------------------+
| User LED 1           | Heartbeat            | Green: This LED is       |
|                      |                      | should always be         |
|                      |                      | blinking about once a    |
|                      |                      | second. If solid off or  |
|                      |                      | solid on, the board is   |
|                      |                      | not executing correctly  |
+----------------------+----------------------+--------------------------+
| User LED 2           | eMMC                 | Green: This LED blinks   |
|                      |                      | during accesses to eMMC  |
+----------------------+----------------------+--------------------------+
| User LED 3           | SD                   | Green: This LED blinks   |
|                      |                      | during accesses to SD    |
|                      |                      | Card                     |
+----------------------+----------------------+--------------------------+
| User LED 4           | currently unassigned | N/A                      |
+----------------------+----------------------+--------------------------+
| Wifi                 | Wifi                 | Yellow: This LED blinks  |
|                      |                      | during network accesses  |
|                      |                      | over Wifi                |
+----------------------+----------------------+--------------------------+
| BT                   | Bluetooth            | Yellow: This LED blinks  |
|                      |                      | when Bluetooth is being  |
|                      |                      | used                     |
+----------------------+----------------------+--------------------------+

安卓图片

安装基于 Android 的图像时，下表定义了 LED 使用/行为。

+----------------------+----------------------+--------------------------+
| LED Board Identifier | Description          | Behavior                 |
+----------------------+----------------------+--------------------------+
| User LED 1           | currently unassigned | Green:                   |
+----------------------+----------------------+--------------------------+
| User LED 2           | currently unassigned | Green:                   |
|                      |                      |                          |
+----------------------+----------------------+--------------------------+
| User LED 3           | currently unassigned | Green:                   |
|                      |                      |                          |
|                      |                      |                          |
+----------------------+----------------------+--------------------------+
| User LED 4           | Boot                 | This LED illuminates at  |
|                      |                      | at the start of boot     |
|                      |                      | and turns of after       |
|                      |                      | completion of boot.      |
+----------------------+----------------------+--------------------------+
| Wifi                 | Wifi                 | Yellow: TDB              |
+----------------------+----------------------+--------------------------+
| BT                   | Bluetooth            | Yellow: TBD              |
+----------------------+----------------------+--------------------------+

对于 Linux，当前 4 个用户 LED 中的 3 个正在被操作系统使用，但用户 LED 4 未使用，可以使用以下命令行打开：

// turn on user LED 4 on Linux.
//     use backslash to escape the colon which is part
//     of the pseudo file name of "apq8016-sbc:green:user4".
echo 1 > /sys/class/leds/apq8016-sbc\:green\:user4/brightness

// turn off user LED 4 on Linux
echo 0 > /sys/class/leds/apq8016-sbc\:green\:user4/brightness

对于 Android 5.1，4 个用户 LED 中有 3 个可用。用户 LED 可通过/sys/class/leds三个用户 LED 的伪文件路径访问：led1、led2和led3. 例如，要打开和关闭用户 LED 1，请使用以下命令行。对于用户 LED 2 led1，在路径中替换led2为 ，同样对于用户 LED 3 led，在路径中替换为led3。

// turn on LED 1 on Android
echo 1 > /sys/class/leds/led1/brightness

// turn off LED 1 Android
echo 0 > /sys/class/leds/led1/brightness