BeagleBone Black Debugging

Javier Vega | December 11, 2019

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Introduction

In this article, I will describe how to setup a serial cable for debugging your BeagleBone Black. As an embedded developer, it is crucial to understand what your board is doing as it initializes. If you experience booting issues, you want to gather as much information from the early stages of initialization. This will give you a better understanding of the issues, instead of randomly trying to solve unknown problems.

For example, you build a server for the BeagleBone Black. You want the server to start running as soon as the BeagleBone boots, so you add it to the initialization script. After booting the board, the server is not running and you have no clue why. To find a solution, you first need to find the problem using a USB-to-TTL Serial Cable. It becomes impossible to find issues of this kind without knowing were the system stopped working. A serial cable is also fundamental when building a new Linux distribution. It helps you find issues in the BootLoader or the Linux Kernel as they start to execute.

Requirements

• A Linux machine running Ubuntu 18.04+
• screen Linux tool, to install it run sudo apt-get install screen

General Steps

1. Connect your USB side of the serial cable to your Host machine.

2. Connect the wires to the J1 header pins of the BeagleBone Black following the table below:

   Board	Cable
   Pin 1 (GND)	Black (GND)
   Pin 4 (RX)	Green (TX)
   Pin 5 (TX)	White (RX)

3. Open a Terminal Window and run ls /dev/tty* to look for the USB device. If you see ttyUSB0 or ttyUSB1, then your serial is connected.

4. To establish a connection, run screen /dev/ttyUSB0 115200.

Once you boot you BeagleBone Black, you should see messages from the BootLoader and the Linux Kernel on your terminal.

Writing screen Output to a File

There are times that is difficult to see the errors on a live Terminal Window because the messages are printed too fast. If you want to log to a file, run screen -L /dev/ttyUSB0 115200. This will create a file screenlog.0 in the current directory. To open the file, run nano screenlog.0.

Resources

How to connect the BeagleBone Black