Re: Spontaneous death/resurrection of USB ports?

This could be either hardware or software. IOUSBFamily has a few locks used to synchronize access to the USB bus. For example, there can only be one device at address 0, so we will block other access to the bus while a device is being reset/addressed. If your device fails to enumerate, the devZeroLock should be cleared, but I could imagine a bug where this doesn't happen -- if so, that USB controller can't accept any more attaches, and you would need to reboot to recover. If you can help us reproduce this, then a level 6 log (from USB Logger or the Logging tab of USB Prober) will probably allow us to pinpoint and fix the problem.

As a hardware problem -- the lack of USB VBUS power (due to an overcurrent condition) will stop USB devices from working/enumerating. Seems unlikely, but it is possible -- particularly since you indicate that you have to leave everything powered off for "a few minutes".

David Ferguson

USB Software Team

Apple Computer

On Jun 23, 2006, at 5:09 AM, Dan Smith wrote:

I'm playing around with prototype USB hardware, specifically the Cypress EZ-USB board. Naturally I'm frequently resetting the board, plugging and unplugging it, and running buggy firmware on the board and buggy applications code on the host. The applications code calls IOKit at application level; no kernel code is used.

About once or twice a week, the USB port I am using will appear to die. The IORegistryExplorer no longer "sees" our device, and it no longer "sees" other devices plugged into that port. Powering down everything, waiting a few minutes, and powering everything up appears to restore normal operation.

I am using both a Power Mac G5 and an Intel Core iMac. I've had the problem occur with both of them.

I can't be sure, but I don't _think_ this is an electrical power issue. I believe that modern circuits have protective devices that are like silent solid-state circuit breakers that reset automatically, so something like this could be happening, but I don't think so. I _think_ it is only software violence that is being committed.

Has anyone experienced anything like this? Does anyone know of softwares sins (or USB protocol sins) that would cause OS X to decide to quit paying attention to a USB port, or something like that?
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	>Spontaneous death/resurrection of USB ports? (From: "Dan Smith" <email@hidden>)