Warp CAN be powered by USB and the battery is not required! However… not all USB ports are made equal, and some USB ports just can’t supply enough power for Warp during certain operations.

We’ve seen this issue come up with USB  2.0 ports in particular. The max limit of USB 2.0 is typically around 500mA at 5V and sometimes the surge currents just can’t be supplied. The mode of failure varies: sometimes the board will fail an operation like an eMMC write but continue operating, other times the system might hang or reboot.

In our office, we use USB 3.0 hubs or charging ports that can supply at least 1A and they seem to all power Warp fine.

If you’re using the Interposer board, you can use two USB cables to power Warp just fine from USB 2.0. Just make sure you have the right jumpers enabled (Install the jumper for “Use Debug VBUS” & and set “WARP Battery Source” to “DCIN”). Of course you could also use the 12V DCIN but you might already be using two USB cables.

FYI when powering off battery, you won’t see these issues either. Even when connected via USB 2.0 with limited supply, the battery can help as a backup power source and allow the board to run fine.

Building Android for the first time can be an aggravating and time consuming process. Following these step-by-step instructions should result in a working build environment and a successful Android build with all the images that are needed to run Android on WaRP, including the bootloader, kernel and Android system and recovery partition.

This guide was written starting from installation of Ubuntu Desktop 14.04.2 LTS on a VM. Users

Important Notes

• Building Android requires approximately 50GB of free disk space.
• Downloading all the pre-requisite files during the ‘repo sync’ step can take more than an hour depending on connection speed.
• Building Android can take a few hours, depending on the speed of your machine.

Getting Started

This guide was written using a VM (VMWare or VirtualBox should both work fine).

VMWare Workstation (Free Trial)

VirtualBox (Free)

64-bit Ubuntu Desktop 14.04.2 LTS (64-bit version required. 32-bit version will not build Android)

On first boot of Ubuntu, install system updates

If using VMWare, install VMWare Tools now.

Install OpenJDK6

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java6-installer
sudo apt-get install bison git gperf libxml2-utils make zlib1g-dev:i386 zip
sudo apt-get install g++-multilib 
sudo apt-get install liblzo2-dev:i386

Install gcc and g++

sudo apt-get install gcc
sudo apt-get install g++

Configure git user and email

git config --global user.name "FirstName LastName"
git config --global user.email username@domain.com

Installing vim/gvim
I use gvim for source editing. Because this is a fresh Ubuntu install, go ahead and install your text editor of choice.

sudo apt-get install vim-gtk

Install repo

mkdir ~/bin
PATH=~/bin:$PATH

curl https://storage.googleapis.com/git-repo-downloads/repo &> ~/bin/repo
chmod a+x ~/bin/repo

Initialize and download Android repository (source code)

Warning: ‘repo sync’ step downloads the source repository and can take a long time depending on connection speed.

mkdir WaRP_Android
repo init -u https://github.com/warpboard/platform_manifest/ -b warp/imx_open_jb4.3_1.1.0-ga
repo sync

Set up environment variables

Add the following lines to ~/.bashrc to define the machine architecture and cross compiler.

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnueabi-
export PATH=~/bin:$PATH

# Android build specific defines
export USE_CCACHE=1

Not required, but I like to use these grep and find aliases when working with the kernel. They can be added to ~/.bashrc

alias sgrep='grep --include={*.c,*.h} -rn "./" -i -e'
alias kgrep='grep --include={Makefile,Kconfig} -rn "./" -i -e'
alias sfind='find . | grep'

Build Android
We should be all ready to build now!

source build/envsetup.sh
lunch warpboard-eng
make -j4

Build outputs
Congratulations, you should now have successfully built images that you can load onto your WaRP board.
Images should be located in the directory:

~/WaRP_Android/out/target/product/warp

Additional External Resources
Official Android Instructions for Initializing a Build Environment

There are a variety of reasons why the push buttons on the WaRP may not be behaving as intended. This guide will help determine if the cause is due to configuration, firmware, software or a hardware issue.

First, from a serial console adb shell, check that /dev/ttymxc2 is configured correctly:

root@warp:/ # stty -F /dev/ttymxc2
stty -F /dev/ttymxc2
speed 115200 baud; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>;
eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; flush = ^O; min = 1; time = 0;
-brkint -icrnl -imaxbel
-opost
-isig -icanon -iexten -echo

If the baudrate is not 115200 or if other settings are different, communication between the DB and WaRP is likely not working. This can be set manually, but a better solution is to flash the system with the latest Android images.

Next, check whether button presses are being received by the WaRP from the daughterboard by using cat on /dev/ttymxc2. Put it in the background so that it continues displaying UART data received while you move onto the next step.

root@warp:/ # cat /dev/ttymxc2 &
cat /dev/ttymxc2 &

Pressing the daughterboard buttons should now result in the WaRP mainboard receiving and printing messages indicating button down [0] and button up [1] events:

{"BTN0":0}
{"BTN0":1}
{"BTN1":0}
{"BTN1":1}

If messages are not being received, the daughterboard may not be functioning correctly or may have an old firmware. To check the firmware version we can toggle the daughterboard RESET# line using the iMX6SL gpio from the command line, which will cause the daughterboard to report a start-up condition and the firmware version running.

Note that GPIO93 (KEY_ROW2) is valid only for revision 1.10 of the WaRP (pre-production boards). Production boards will use GPIO95 instead.

1. Set up GPIO93 for control from command line
2. Set GPIO93 as an output
3. Set the value of GPIO93 low to initiate a reset
4. Set the value of GPIO93 high to release the reset signal
5. KL16 will reset and send start-up messages, including version number to /dev/ttymxc2

root@warp:/ # echo 93 > /sys/class/gpio/export
root@warp:/ # echo out > /sys/class/gpio/gpio93/direction
root@warp:/ # echo 0 > /sys/class/gpio/gpio93/value
root@warp:/ # echo 1 > /sys/class/gpio/gpio93/value

Start-up message:

{"SYSMSG":"WaRP Daughterboard Started","Version":"0.1beta-20150302"}
{"MMA9553L":"Status","data":{"steps":0,"distance":0,"speed":0,"calories":0}}