Raspberry Pi User Guide

Chapter 3: Troubleshooting

Sometimes, things don’t go entirely smoothly. The more complex the device, the more complex the problems that can occur—and the Pi is an extremely complex device indeed.

Thankfully, many of the most common problems are straightforward to diagnose and fix. In this chapter, we’ll look at some of the most common reasons for the Pi to misbehave and how to fix them.

Keyboard and Mouse Diagnostics

Perhaps the most common problem that users experience with the Raspberry Pi is when the keyboard repeats certain characters. For example, if the command startx appears onscreen as sttttttttttartxxxxxxxxxxxx, it will, understandably, fail to work when the Enter key is pressed.

There are typically two reasons why a USB keyboard fails to operate correctly when connected to the Raspberry Pi: it’s drawing too much power, or its internal chipset is conflicting with the USB circuitry on the Pi.

Check the documentation for your keyboard, or the label on its underside, to see if it has a power rating given in milliamps (mA). This is how much power the keyboard attempts to draw from the USB port when it’s in use.

The Pi’s USB ports have a component called a polyfuse connected to them, which protects the Pi in the event that a device attempts to draw too much power. When this polyfuse is tripped, it causes the USB port to shut off, at around 150 mA. If your keyboard draws anywhere around that much power, it may operate strangely—or not at all. This can be a problem for keyboards ...