CM-FX6: Android: Operating instructions

Overview

This page contains information useful for day-to-day operating of CM-FX6 Android package.

Display configuration

By default CM-FX6 is configured to use HDMI display with 1080p resolution.
This setting can be overridden by providing alternate boot arguments to the Android/Linux kernel.

• Connect to the serial console as explained in the Development section.
• Press ENTER to stop the countdown.

setenv videomode video=mxcfb0:dev=hdmi,if=RGB24,1920x1080M@60 video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off    # default video mode (HDMI)
setenv videomode video=mxcfb0:dev=dvi,if=RGB24,1920x1080M@60 video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off     # DVI display with 1080p resolution
setenv videomode video=mxcfb0:dev=dvi,if=RGB24,1280x1024M@60 video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off     # DVI display with 1280x1024 resolution
setenv videomode video=mxcfb0:dev=lcd,if=RGB24,KD050C-WVGA video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off       # Startek 800x480 LCD

• Type in boot to proceed to kernel boot overriding default video mode.

ON/OFF button

ON/OFF button suspends and resumes CM-FX6 operation (i.e. sends to sleep / wakes up), whenever suspend is not disabled manually, or by Android policy.
Pressing and holding the ON/OFF button for more than 5 seconds, will unconditionally power the module down. This operation is pretty much equivalent to unplugging the power supply, so it should really be considered the last resort.

Graceful shutdown

Due to specifics of i.MX6 SoC hardware, the ON/OFF button cannot be used to bring up the Android Power off menu.
CM-FX6 pre-configures GPIO 29 (P18, pin 2 on SB-FX6 base board) as GPIO Power Button. As GPIO 29 has an internal pull-up resistor, it can be momentarily connected to the ground to produce a 'power button press'. Short press will behave identically to short press on ON/OFF button, whereas long press will bring up the Power off menu allowing graceful shutdown.

Security

CM-FX6 Android package permits full root access.
The su utility will switch a user to root not requiring any credentials or password.
In order to harden system security one might replace su implementation or remove it altogether.

Start-up script

/system/etc/install-recovery.sh script is run upon system boot by Android init process.
As system partition is mounted 'read-only', one should remount system 'rw', prior to attempting to edit the script.

For devices running Ice Cream Sandwich

Networking

Normally, when both networking interfaces are enabled (Ethernet, Wi-Fi), CM-FX6 Android will tear Wi-Fi down preferring Ethernet.
In order to override this policy, enabling Ethernet and Wi-Fi co-existence, proceed to the console, and type in:

# setprop compulab.net.disable_policy true    # (or 'y', or '1')

S/PDIF audio

Normally, Android audio streams to HDMI or analog audio codec according to configuration.
In order to switch audio output to S/PDIF, proceed to the console, and type in:

# setprop compulab.audio.spdif 1