posted by wap, platform: iPhone
要带供电隔离的
5口以上
给树莓派4用 买了两个都是usb 反向充电 导致只要插上usb hub树莓派就不能启动
抓狂

引用:

原帖由 zxsoft 于 2021-5-22 16:48 发表
posted by wap, platform: MAC OS X
没看懂你说的是把树莓派的电源插在USB HUB上，还是把USB HUB插在树莓派上。如果是前者的话，你先考虑一下功率和供电方式。你要同时使用几个树莓派。一个树莓派4B的电源是5V3A,所以 ...

树莓派4所有usb都是接到供电电路
usbhub 接上以后 如果usbhub没有电源隔离 它回又电流流回树莓派usb口
这样就干扰树莓派的供电电路 树莓派就启动不起来
所以需要一个 带电源隔离的 usbhub 让它不反向充电
具体看这个讨论
https://www.raspberrypi.org/forums/viewtopic.php?t=244900

这是个野生解决方法 但是我动手能力不行
I currently have a Raspberry Pi 4 8GB with 2 USB 3 4 port hubs connected to 4 Hard Drives (18Tb total) as well as USB 3 SSD enclosure for USB booting. I am using it as an enhanced RAID system.

The problem is all these cheap 4 port USB 3 hubs that you find on both eBay and Amazon are very poorly designed. The external 5V is connected to both Upstream and Downstream VBUS which causes confusion in the Raspberry Pi USB controller and the back powering problems. It has been suggested to cut the red cable (VBUS Upstream) between the Pi and the USB hub, however this is only half the job. I have found that just cutting the red cable with my connected Hard Drives the Pi would randomly not recognised the attached Drives or not see the Drives after a reboot. I have also found that the Hard Drives would not reset or enter standby after a reboot leaving the Drives in a active state.

The only way was to send a software reset to the USB hub or disconnect and reconnect the Drive for the Pi to see the Drives which is a right pain.

:idea: The way round this problem is to disconnect the Pi Upstream VBUS Red Cable and connect it to the reset circuit of the USB Hub Controller chip. The USB Hubs I have been using have either a GL3510 or GL3520 Controller chip and both the external 5V rail and the Upstream VBUS are both connected to the reset circuit, so there is no way of resetting the Controller chip by lowering the Upstream VBUS. You need to lift one end of R1 disconnecting that end from the external 5V rail and solder the Pi Upstream VBUS cable to the other end of R1.