问题描述
我正在使用Raspberry Pi 3 Model B上的USB端口通过USB磁性充电电缆为配件充电.我想检测何时插入电缆并从Pi上拔出 .
I'm using a USB port on the Raspberry Pi 3 Model B to charge an accessory via a USB magnetic charging cable. I want to detect when the cable is plugged in and removed from the Pi.
我一直在插拔电缆,寻找在Linux上检测到的任何痕迹.到目前为止,我已经尝试过:
I've been plugging in and removing this cable and looking for any traces of this being detected on Linux. So far, I've tried:
- 通过
udevadm monitor
监视udev事件. - 在
/var/log
等中设置系统登录的尾巴. - 在
/dev
目录上运行inotify监视以查找新设备 - 在
/sys/bus/usb/devices
中四处寻找线索
- monitoring udev events by
udevadm monitor
. - tailing the system logs in
/var/log
etc. - running an inotify watch on the
/dev
directory for new devices - looking around in
/sys/bus/usb/devices
for any clues
是否可以检测到我插入/拔出的简单充电电缆?凭直觉,我认为没有(因为电缆仅用于充电,并且没有驱动程序),但是我观察到插入电缆时RPI闪烁其内置的LED红色.
Is it possible to detect my simple charging cable being inserted/removed? By intuition I would think no (since the cable is purely for charging, and doesn't have drivers), however I observe that the RPI flashes its builtin LED red when I insert the cable.
推荐答案
无需花费大量精力(硬件或黑客),
Without significant effort (hardware or hacks), No.
您观察到的红色LED闪烁是Pi的功率监视器,指示当电流开始流向附件时电压突然下降.该LED指示灯指示电压(电能)已短暂下降到稳定水平以下,并且可能导致系统不稳定.
The red LED flash you observe is the power monitor for the Pi indicating a sudden voltage drop as current begins to flow to your accessory. This LED indicates voltage (electrical energy) has briefly dropped below stable levels, and system instability may result.
由于连接纯粹是在充电(没有与Pi交换USB数据),因此操作系统不知道该设备已连接.您可以构建一个外部电流测量电路来检测外围设备的汲取功率,但是在电子堆栈交换中最好解决这个问题.
As the connection is purely charging (no USB data exchanged with the Pi) the operating system has no idea the device is connected. You could build an external current-measuring circuit to detect the peripheral drawing power, but such a question is better off in the electronics stack exchange.
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