CM-T335: Linux: Debian

Overview

The example run-time Linux filesystem image for CM-T335 is based on Debian GNU/Linux Sid. The CompuLab Linux package for CM-T335 includes ready to run NAND flash image, Linux kernel configuration and source code patches, and an archive of the root filesystem, used to create the image.

The default Debian Sid Linux image includes more than 400 software packages. Among them:

• Core system
• Debian package management system
• X11 Windowing System
• Enlightenment desktop manager
• Netsurf web browser
• Samba connectivity suite
• SSH and FTP server and client
• ALSA configuration and usage utilities
• CAN Bus utilities
• Bluetooth tools and daemons

The Getting started with Linux on CM-T335 page provides a brief introduction on how to install the run-time Linux image. This article describes package structure and peripheral device options specific to the CM-T335.

Package contents

version.txt

The contents of the version.txt identifies the package version.

images

• uImage-cm-t335 - ready to run Linux kernel image binary for CM-T335
• debian-image.tar.bz2 - archive of the Debian root file system
• kernel.img - Kernel image required for installation onto the NAND flash
• ramdisk.img - Ramdisk image required for installation onto the NAND flash
• bootscr.img - U-Boot script used for image installation

kernel

• uImage-3.2.0-cm-t335-1.1.bin - ready to run Linux kernel version 3.2.0-cm-t335-1.1 for CM-T335
• linux-3.2.0-cm-t335-1.1.config - Linux kernel 3.2.0-cm-t335-1.1 configuration file
• linux-3.2.0-cm-t335-1.1.patch - patch vs. b81bf04091986fa3893f31955564594567be3b61 commit in the Linux Integration/Staging Tree for AM33x SoC by Arago progect with support for CM-T335 peripherals
• patches - ordered collection of patches, that form the single patch above (linux-3.2.0-cm-t335-1.1.patch)
• modules_3.2.0-cm-t335-1.1.tar.gz - a modules tarball, that matches the ready to run Linux kernel (uImage-3.2.0-cm-t335-1.1.bin)

utilities

The utilities directory contains miscellaneous utilities useful for development

• tftpd32.zip - TFTP server for Windows users
• eeprom-util - CompuLab EEPROM utility for reading information found inside the EEPROM on CompuLab boards
• bootscr.src - U-Boot script source used for loading kernel and ramdisk images from MMC/SD card.
• debian-image.cfg - configuration file used by ubinize utility for debian-image.ubi generation. For more information about UBIFS images please refer to the Linux Development for ARM modules article.

Using Debian Linux on CM-T335

Connection and Logging In

Use the following usernames and passwords to login:

Account with administrative privileges:

User: root
Password: 111111

Regular user account:

User: user	
Password: 111111

In addition to these accounts CM-T335 allows anonymous FTP access. To login into the Linux system, you may use a serial console (ttyO0) at 115200 bps, or connect through the network, or use a keyboard and DVI/LCD display (tty1, tty2, tty3, tty4).

Networking

To configure networking, edit /etc/network/interfaces, /etc/udev/rules.d/70-persistent-net.rules, /etc/resolv.conf, /etc/hostname and /etc/hosts. For more information about Debian Linux network configuration read Network setup chapter in the Debian Reference.

Consoles

The Linux file system image is designed to suit different kernel versions and configurations. Therefore, during the operating system startup, consoles at several serial ports and DVI/LCD display are enabled. Some of these devices may not be supported, either because of kernel versions incompatibilities, or because the kernel was not configured to support these devices. When the console is enabled for such a device, the following or similar message can appear on active console:

INIT: Id "T0" respawning too fast: disabled for 5 minutes

This is not an error message, it is just a warning that can be eliminated by editing /etc/inittab file.

X Windows system

The CompuLab distribution contains full featured X Windows system with Enlightenment 17 window manager. Before starting X Windows, connect USB mouse and keyboard to the system. You can run X Windows by typing startx.

Enlightenment 17 window manager has a built in configuration set up to work best with phones, tablets and similar devices. To activate the "touchscreen" profile, enter Main->Settings Panel->Settings->Profiles. Select the Touchscreen profile.

To switch back to the standard profile, please see the Known Issues article.

Software Management

The Debian Linux image for CM-T335 includes all the information required to use Debian package management utilities. You can use apt-get and dpkg out of the box.

GPIO access

Linux provides simple and convenient GPIO access via sysfs interface. A GPIO should be exported using /sys/class/gpio/export. After the GPIO is exported it is possible to change its direction and value using /sys/class/gpio/gpioX/direction and /sys/class/gpio/gpioX/value attributes.

Example

The following example demonstrates how to configure GPIO 64 as output and set value to high:

echo 64 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio64/direction
echo 1 > /sys/class/gpio/gpio64/value

The above example assumes that the corresponding pin is set to mux mode 7 and the GPIO 64 is not requested in the Linux kernel.

See also

• CM-T335: Linux: Getting started
• CM-T335: Linux: Kernel
• Linux: Development for ARM modules
• Linux: Debian: Minimal ARM filesystem
• Debian Reference.