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USB, although simpler to use than SCSI, is far from problem-free. If you are having trouble getting a device connected to the USB port to work, consider the following:

Check for power If the device has a separate on/off switch, make sure it is on. If the device has a separate power supply, make sure it is plugged in. If a USB device does not work at first, give it several minutes to warm up.

"Not enough power" errors: use a powered hub for multiple devices If you are going to add several USB devices, consider getting a USB hub. This may even be required if you have USB devices that only have a single port (thereby preventing you from chaining additional devices to them). Because the USB port supplies its own power, the hub need not have a separate power supply. However a powered hub is recommended, as it will minimize problems that may occur due to a device not getting sufficient power. This is especially likely to be the cure if you get a message that says: The device can't operate because it needs more power than is available or The device may not provide all of its functions because it requires more power.

Sometimes, this error may be due to a bug in the Mac OS ROM file software. Upgrading (or downgrading, if you are already using the latest version) to a different version of the ROM file may eliminate the error.

Failure to shut down? Check if it's caused by a USB hub or other USB device If you select the Shut Down command and your Mac restarts instead of shutting down, this could be due to a USB device connected to your Mac. This happens most often with USB hubs. Sometimes zapping the PRAM (see Fix-It #9) or doing a clean install of the system software (see Fix-It #4) will fix this. Otherwise, the solution will likely require fixing or replacing the problem USB device.

Reconnect and/or switch cables (especially for startup and shut down problems) Try disconnecting and reconnecting the suspected problem device to its USB port. Also try switching ports on the Mac itself. That is, move the cable from USB Port 1 to USB Port 2 (or vice versa).

Note: There are two types of USB ports (Type A, as found on the Mac, and Type B, as used on many external devices). To connect a USB device to your Mac, you will need a cable with the matching connectors on each end.

USB devices have been implicated in some wake-from-sleep crashes (see Chapter 14), as well as various startup and/or shut down freezes. The usual work-around is to disconnect or power down the problem USB device before taking the action that triggers the freeze (e.g., disconnect the USB device before starting up and then reconnect the device when startup is over). The permanent fix typically requires getting updated versions of relevant USB driver software (either from Apple or from the vendor of the problem device). If you get a wake-from-sleep freeze, you can often regain control of the Mac via a Force Quit (Command-Option-Escape); restarting the Mac is not typically required (see Chapter 4 for more on freezes).

More generally, turning a USB device on before you start up may solve some problems. Other times, turning it on only after the startup sequence is over may be what is needed to succeed. Not totally unlike SCSI, there is a bit of "voodoo" developing here as to what will or will not work.

"No driver found" error: check for USB software USB devices often ship with their own driver software, needed for the device to work. These drivers are installed in the Extensions folder. Make sure they are installed. The Mac OS will generate a No Driver Found message if the Mac checked for a driver for the USB device you just connected but could not find one. Install (or re-install) the driver as needed.

Apple now includes a set of USB drivers with the Mac OS. They have names such as USB Support, USB Device Extension, USBPrintDriver, and USB Mass Storage. In many cases, these files can serve as substitutes for the device-specific USB drivers that ship with a device. So if you are having problems getting the Mac to recognize a USB device, try removing its driver software from the Extensions folder. Surprisingly, this might be the solution!

Note: Some of these USB files are built-in to the latest versions of the Mac OS ROM file, so you may have them installed even though you do not see their names in the Extensions folder.

Use Apple System Profiler: disable drivers as needed One way to check for a possible problem with a USB device is to use Apple System Profiler. Select its "Devices and Volumes" tab. If a USB device is currently recognized by the Mac as properly connected, it will be listed there. If not, it typically means either that the needed software driver is not installed or there is a hardware-related problem. For example, it may mean that you need to separately connect the device to a powered USB hub rather than to a chain of USB devices connected to the Mac's USB port.

If the device is shown in the Apple System Profiler, but does not work, it most often means a problem with the device's USB driver. You either need to update to a newer version of the driver, eliminate the driver (in favor of using Apple's default drivers), or resolve a conflict with another USB driver.

For example, I could not get my SuperDisk drive to work after updating to Mac OS 9. The solution was to delete the SuperDisk drivers installed by the SuperDisk Installer and go with the Mac OS 9's "built-in" drivers. Later, I once again could not get the SuperDisk drive to work. This time, I discovered the problem was the Olympus USB SmartMedia card reader drivers that I had just installed. If I deleted them, the SuperDisk worked. With such conflicts, you may be able to fix things by switching the loading order of the drivers (assuming that there are drivers for each device in the Extensions folder; sometimes the driver is instead built in to the Mac OS software). Otherwise, you will simply have to enable and disable the relevant drivers (and likely restart) each time you need to switch to use a given device.

  • SEE "Take Note: Booting From Devices Connected To Ports," earlier in this chapter, for information about starting up from a USB drive.

Check for Apple updates

USB drivers Apple continues to update its USB drivers. There may be a newer version than the one you are using that fixes a problem you are now having. Check on Apple's Web site for updates (or, if you are using Mac OS 9, you can use Apple's Software Update control panel).

InputSprockets If you are using your Mac to play games, and especially if you are connecting USB peripheral devices (such as a game pad or joystick), also be certain to get Apple's latest InputSprockets files: USBHIDUniversalModule and a collection of extensions that all begin with the word InputSprockets. One version of these files should be included on your Mac OS system software CD and were probably already installed on your hard drive when it first arrived. However, Apple's Web site may have newer versions.

Other updates For example, in late 1998 Apple released iMac Update 1.1. Apple stated that it "improves the iMac's ability to identify USB devices when starting up, improves the startup time when many USB devices are connected, and enables new USB solutions." The update was simply a replacement for the Mac OS ROM file in the System Folder, presumably with updated USB-related code. Apple will likely have further updates along these lines.

Special problems with USB printers Even if the device is connected correctly and drivers are installed, you may get one or more of the following problems:

  • An alert may occur during startup stating that the software needed to use the device could not be found.

  • An alert that AppleTalk is active and the serial port is in use may occur after selecting the printer icon in the Chooser.

  • A −192 error (resource not found) may occur when trying to print

  • The printer may not appear at all in the Chooser.

  • The printer may refuse to print for various other unspecfied reasons.

In all of these cases, the problem is usually traced to the printer driver software or the Apple firmware. In particular, make sure you are using the latest versions of the driver software and especially make sure it is a USB-specific version of the driver. The same printer may have a serial-port version of the driver. This driver will not work with a USB version of the printer.

USB modem If you have an external USB-connected modem, the Modem control panel should list the USB modem as a new option in its "Connect via" pop-up menu. This is what you should select.

Try general troubleshooting Beyond this, if your problem has not been solved, it's time for more general troubleshooting, such as checking for an extensions conflict.



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