BBB Finding your way around

Beagle Bone Black - Finding your way around

The aim of the article is to provide a stepping stone on the learning curve between high level familiarity with Linux (and perhaps Arduino development) and the lower level Beaglebone.  The article attempts to bring together information, which is otherwise presented disparately, in a brief and to the point format.  As such, the article is not really suitable for complete beginners. 

The article presents a series of notes, produced after investigation of the Beaglebone Black (BBB) using an iMac running OSX 10.8.4 (Mountain Lion).  Reference to PC Host and Mac are mainly interchangeable, as are references to the operating systems OSX, Linux and Windows.

Where a native Linux host PC is not available, a virtualised installation is highly recommended.

Introduction 

The BBB is a SoC credit card computer which runs Linux, out of the box.

Power

Power is supplied to the board by

• + Micro USB connector

A suitable cable is supplied with the board which it is advisable to use.  Some otherwise similar cables are not able to meet the current requirements (460mA@5V) during boot and cause the BBB to shutdown before the boot cycle is complete

• 5V, 2.1mm centre positive, male barrel connector

The BBB documentation specifies a tolerance of +- 0.2V

Storage

Device storage is provided by two devices  

• On board flash (2GB), referred to as eMMC
• Micro SD Card, referred to as MMC or SD
• DDR3 RAM (512MB)

User I/O

User I/O is provided by three devices

• KVM. Keyboard, HDMI video, Mouse.

Notes:  HDMI output is by way of a micro HDMI cable which needs to be sourced separately.  There is only one full size USB host connector. An external powered hub is required for simultaneous connection of keyboard and mouse.

• Micro USB port

The micro USB port provides an interface for a host PC to connect to the BBB, by VSP (virtual serial port) or SLIP (IP over serial). Drivers must be installed on the host PC.  By default, the virtual serial port is configured at 115200, 8, n, 1.  The BBB SLIP IP address is configured as 192.168.7.2 and the host PC appears as 192.168.7.1

•  Ethernet port

The 10/100 Ethernet port is configured to obtain IP parameters using DHCP.

User Access

The BBB uses an Angstrom Linux distribution, with a blank root password.  

The BBB User I/O interface devices provide several user interaction mthods. 

• KVM, access to a Gnome desktop environment.
• VSP, access to a console session, reached using any suitable terminal.  E.g. screen -B 115200
• SLIP, access to a console session via SSH.  Access to the the desktop is provided by a VNC server.
• Ethernet, provides access to a console session via SSH.  Desktop access is provided by a VNC server. 

An X11 environment is used to render the GUI but the author has yet to find a way to remotely connect to the graphical desktop using X.

Web Browser Access

The BBB runs a HTTP web on port 80 which is reachable from the Ethernet or SLIP interface.

The web server provides access to Beaglebone 101 support resources

• Angrstrom and update how to 
• Cloud9 IDE, Javascript development environment.
• Various Cloud9 demonstrations
• GateOne Java based SSH client, which may fail as Java based SSH clients are want to fail.
• Various other support links

When tethered to a host PC by the micro USB connector, a removable drive is mounted on the host PC

The removable drive BEAGLEBONE, contains a START.htm file which loads HTML pages containing

• Getting Started Guide
• Documentation
• Host PC Drivers
• Links to troubleshooting and other support resources

Boot

The BBB supports booting from

• Onboard flash (eMMC), default
• SD Card (MMC)
• Network boot

The documentation indicates SD Card boot is initiated by pressing the User Boot button, near the micro HDMI and full size USB host ports, during power up.  This appears to be unreliable and the BBB may boot from the SD Card whenever a valid boot image is found on the card.

The BBB is fitted with a bank of four (blue) user configurable LEDs.  As shipped, the two LEDs closest to the Ethernet connector indicate I/O access to the eMMC and MMC, which can be useful for identifying the active boot device, during the boot process.

User LED layout

The User LEDs are a bank of four LEDs, fitted to the board edge between the Ethernet and Reset buttons.  The function of these LEDs is configurable from software.  

As shipped

[ethernet] [eMMC LED] [MMC LED] [LED1] [LED0] [Reset Button]

SD Card Boot layout

Bootable SD Cards contain two partitions.  The parition numbers used below are notional.

• Part0 is formatted as VFAT and contains the boot loader and boot image.
• Part1 is formatted as EXT3/4 and contains the root file system of the Linux distribution.

Part0 contents

• ID.txt text file containing board ID and version information
• uEnv.txt text file containing boot loader options
• MLO binary
• u-boot.img binary boot loader image

Part1 content

/  The Angstrom distribution rootfs, containing the kernel image and application binaries, amongst many other things.

/media/BEAGLEBONE The mountable removable disk, made available to a tethered Host PC. Contains documentation, getting started guide and host driver files.

With the SD Card inserted into a Debian Linux host with a single hard disk, the partitions can be mounted.

To mount the boot loader parition

mount -t vfat /dev/sdb1 /media/sdcard1

To mount the rootfs

mount -t ext4 /dev/sdb2 /media/sdcard2

Onboard Flash (eMMC) Content

Bootable SD cards may be configured to image their content to the onboard flash (eMMC) at the end of the boot process.  By default, the BBB eMMC contains the boot and rootfs partitions of the Angstrom distrubution the board was shipped with.

BBB eMMC partitions. Boot partitions can not be mounted 

• /dev/mmcblk0  Boot disk
• /dev/mmcblk0boot0  Boot loader parition
• /dev/mmcblk0boot1  Boot loader parition
• /dev/mmcblk0p1 Beaglebone 101 content /media/BEAGLEBONE
• /dev/mmcblk0p2 Angstrom distribution rootfs