Chapter 6. Recovering from the Mistakes

You can try to avoid mistakes, but sometimes they just happen. In this chapter, we will look at what to do after a mistake happens. While the Beagle board is designed to be robust, part of doing embedded things can involve interfacing with different hardware. Even if you haven't made a mistake before, learning the diagnostic procedures in this chapter will assist you in taking necessary precautions.

In this chapter, we will cover the following topics:

• Diagnosing different conditions with the help of LEDs

• Troubleshooting the BeagleBone with a serial port

• Repairing options

When a mistake happens, do not panic.

Tip

For more serious mistakes resulting in a fire or injuries to you or anyone else, or anything that might threaten either you or anyone else, please contact the local emergency authorities immediately!

For less serious mistakes that do not involve an immediate threat or harm to you or anyone else, take a moment to evaluate the situation and avoid compounding...

Symptoms of the mistakes

Most mistakes will lead to a few common symptoms. We will focus on the following symptoms:

• The web server on the BeagleBone is inaccessible

• SSH no longer works; you will either get an error about no such host or invalid password

• SSH appears to work, but you are immediately disconnected

• Nothing happens when you connect power to the board

The goal of this chapter is to identify problems that can be repaired with the help of software. The board is designed in such a way that it can be recovered after almost any software fault. We have intentionally not gone through the causes. For beginners, it is often very hard to identify the specific steps that lead to the problem.

Troubleshooting the BeagleBone

We will go through evaluating the board and then attempt to classify the types of problems. It is important to keep in mind that a perfect diagnosis is a difficult thing to do. The part with the LEDs can be partially done without any additional equipment. For the BeagleBone Black (BBB), a serial cable can provide a lot more details.

Diagnosing with the help of LEDs

The first step is to observe the LEDs on the BeagleBone. A functional BeagleBone has a power LED light controlled by the hardware. Most BeagleBone system software will, by default, blink the other LEDs to indicate system activity. If none of the LEDs are on, check whether the power is switched on. It is especially important to verify that the BeagleBone is solely powered from the USB port. The USB specification provides up to 500 mA per port but, in some cases, this can be limited to 100 mA. The 100 mA current can cause the BeagleBone to boot and reset. Although 500 mA is available, the BeagleBone...

Repairing the BeagleBone

After going through the previous troubleshooting process with the LEDs and the serial port, if you still do not find a fix, the next step is to look at repair options. The BeagleBone SRM document describes this procedure. Repair requests can be initiated by navigating to http://www.beagleboard.org/support/rma. Once approved, an RMA number will be issued and instructions to ship will be provided. The BeagleBone is then shipped back to the provided address. Depending on the nature of the problem and the length of time for which you have owned the board, there might be a cost associated with it. The concerned authorities should be able to explain this to you. Once they receive the board, they will do additional diagnostics and replace components as needed.

Since the BeagleBone is a low-cost board, the cost to ship and repair can potentially exceed the cost of a new board. For instances like this, it might be best to buy a replacement. For readers outside the U.S., they...

Summary

In this chapter, we looked at ways to recover your BeagleBone from certain mistakes. There are two primary diagnostic information sources for the BeagleBone family. The LEDs, specifically the power LED, can provide immediate information on the state of the BeagleBone. The second important diagnostic tool is the serial port. On the BBB, this requires the optional serial cable. On the BBW, this functionality is built into the board, but there are some potential sequencing problems. With these two diagnostic indicators, you should be able to fix simpler mistakes, often by just merely reinstalling the system software. This same process can also identify boards that are likely to require either a repair or replacement.

With this basic diagnostic process in hand, the next chapter will look at options to interface the BeagleBone with other hardware. If something does go wrong with interfacing hardware, the diagnostic process described in this chapter can give you some insights.