CM-T3730: Linux: Angstrom
Introduction
The example run-time Linux filesystem image for CM-T3730 is based on Angstrom Linux 2012. The CompuLab Linux package for CM-T3730 includes ready to run Angstrom Linux filesystem image, Linux kernel and source code patches.
The default Angstrom Linux image includes more than 1000 software packages. Among them:
- Core system
- X11 Windowing System
- Enlightenment v0.16 desktop manager
- Firefox and Midory web browsers
- MPlayer and omapfbplay media players
- GStreamer with multiple plugins
The Getting started with Linux on CM-T3730 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-T3730.
Package contents
version.txt
The contents of the version.txt identifies the package version.
images
- uImage-cm-t3730.bin - ready to run Linux kernel image binary for CM-T3730
- Angstrom-image-cm-t3730.tar.bz2 - archive of Angstrom root file system
- bootscr.img - U-Boot script used for booting kernel from MMC/SD card with root file system on MMC/SD card
kernel
- uImage-3.0.32-cm-t3730-2.bin - ready to run Linux kernel 3.0.32-cm-t3730-2 for CM-T3730
- linux-3.0.32-cm-t3730-2.defconfig - Linux kernel 3.0.32-cm-t3730-2 configuration file
- linux-3.0.32-cm-t3730-2.patch - patch vs. Linux stable kernel 3.0.32 with support for CM-T3730 peripherals
- patches - ordered collection of patches, that form the single patch above (linux-3.0.32-cm-t3730-2.patch)
oe
The oe directory contains configuration files and CM-T3730 specific package definition for OpenEmbedded.
- base-revision - the OpenEmbedded commit id that was used to create the Angstrom root file system image.
- local.conf - configuration file used to build Angstrom Linux image for CM-T3730. This file should be placed in ${OEBASE}/build/conf directory.
- patches - collection of patches that were applied on top of the commit id in base-revision.
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 used for booting kernel from MMC/SD card with root file system on MMC/SD card
extra
The extra directory contains graphics (SGX) related files inside the Graphics_SDK_4_05_00_03 directory
- gfxsdkdemos.tar.bz2 - archive of ready to run SGX functionality demonstrations
- patches - collection of patches that fix the Graphics SDK v4.05.00.03 compile time errors
Using Angstrom Linux on CM-T3730
Display options
CM-T3730 evaluation platform has four video output interfaces: LCD, DVI, LVDS and TV-out. Default configuration of Angstrom Linux for CM-T3730 uses DVI as primary video output. It is possible to switch between the DVI and LCD interfaces on the fly. TV-out can be used simultaneously with LCD or DVI interface.
Linux implementation of the OMAP3 display subsystem is described in detail in Documentation/arm/OMAP/DSS file in the Linux kernel source tree.
Display resolutions
- The Toppoly LCD supplied with CM-T3730 evaluation kit supports 480x640 resolution with 18 bits per color
- DVI output can be configured for standard resolutions using kernel command line parameter omapfb.mode:
- 1024x768 - omapfb.mode=dvi:1024x768-24@60
- 800x600 - omapfb.mode=dvi:800x600-24@60
- 640x480 - omapfb.mode=dvi:640x480-24@60
- TV-out supports PAL and NTSC standards
Examples
Switch from LCD to DVI
mgr0=/sys/devices/platform/omapdss/manager0 lcd=/sys/devices/platform/omapdss/display0 dvi=/sys/devices/platform/omapdss/display1 fb0=/sys/class/graphics/fb0 w=`cat $dvi/timings | cut -d "," -f 2 | cut -d "/" -f 1` h=`cat $dvi/timings | cut -d "," -f 3 | cut -d "/" -f 1` echo "0" > $lcd/enabled echo "" > $mgr0/display fbset -fb /dev/fb0 -xres $w -yres $h -vxres $w -vyres $h # at this point you have to switch the dvi/lcd dip-switch from the omap board echo "dvi" > $mgr0/display echo "1" > $dvi/enabled
Clone GFX overlay to LCD and TV
ovl0=/sys/devices/platform/omapdss/overlay0 ovl1=/sys/devices/platform/omapdss/overlay1 tv=/sys/devices/platform/omapdss/display2 fb0=/sys/class/graphics/fb0 fb1=/sys/class/graphics/fb1 w=`cat $tv/timings | cut -d "," -f 2 | cut -d "/" -f 1` h=`cat $tv/timings | cut -d "," -f 3 | cut -d "/" -f 1` echo "0" > $ovl0/enabled echo "0" > $ovl1/enabled echo "" > $fb1/overlays echo "0,1" > $fb0/overlays echo "$w,$h" > $ovl1/output_size echo "tv" > $ovl1/manager echo "1" > $ovl0/enabled echo "1" > $ovl1/enabled echo "1" > $tv/enabled
Switch TV-out from PAL to NTSC
tv=/sys/devices/platform/omapdss/display2 echo "0" $tv/enabled echo "ntsc" $tv/timings echo "1" $tv/enabled
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 140 as output and produce a 1usec pulse:
echo 140 > /sys/class/gpio/export echo 1 > /sys/class/gpio/gpio140/direction echo 0 > /sys/class/gpio/gpio140/value echo 1 > /sys/class/gpio/gpio140/value usleep 1 echo 0 > /sys/class/gpio/gpio140/value
Angstrom Linux package management
Angstrom Linux for CM-T3730 includes opkg package manager. It can be run from terminal command line.
