Documentation:AVR32 Linux Development/How to build an embedded Erlang

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As of R13B04, an embedded version of Erlang can be built for the NGW100 using buildroot-2.3.0. Full documentation on cross-compiling Erlang can be found in the xcomp/README file inside the source distribution.


Contents

[edit] Prerequisites

Assuming you've successfully built buildroot-2.3.0 and been able to create a bootable system from it. Next, you'll need a copy of the Erlang sources, available from http://erlang.org/download.html, or by cloning the git repository at http://github.com/erlang/otp.

[edit] Setup

You'll need to set up the following environment variables:

  • ERL_TOP: Points to the top of the Erlang source tree
  • PATH: Must include the avr32-linux-* commands, in $BUILDROOT/build_avr32/staging_dir/usr/bin
  • TARGET_DIR: Desired installation directory on the NGW100, typically /usr/lib/erlang
  • TMP_DIR: Temporary directory for creating the Erlang distribution

For example: 

$ export ERL_TOP=~/Work/otp_src_R13B04
$ export PATH=$PATH:~/Work/buildroot-avr32-v2.3.0/build_avr32/staging_dir/usr/bin
$ export TARGET_DIR=/usr/lib/erlang

[edit] Configuring

There are a number of steps to configure and build Erlang for the NGW100: 

$ cd $ERL_TOP
$ ./otp_build autoconf
$ ./otp_build configure --xcomp-conf=$ERL_TOP/xcomp/erl-xcomp-avr32-atmel-linux-gnu.conf

This will configure a cross compile environment using the settings in the ./xcomp/erl-xcomp-avr32-atmel-linux-gnu.conf file.

[edit] Building

The next step is to build Erlang, this can take a while as it first must build a host-native version in order to compile .erl files, before it can build the avr32 version: 

$ ./otp_build boot -a

[edit] Creating a Release

The next step is to create an Erlang release distribution that can be simply untarred on the NGW100: 

$ ./otp_build release -a $TMP_DIR
$ cd $TMP_DIR
$ ./Install -cross -minimal $TARGET_DIR

Note that $TARGET_DIR specifies where on the NGW100 filesystem Erlang will be located, typically /usr/lib/erlang. 

$ tar czvf /tmp/erlang-dist.tar.gz *

Will create the tar.gz file in /tmp.

[edit] Installation

Use scp to copy the erlang-dist.tar.gz file to the NGW100; don't copy it to /tmp as it likely won't fit, put it in /home/avr32. 

$ scp /tmp/erlang-dist.tar.gz root@ngw.example.net:/home/avr32

Now, log into the NGW100 and type the following commands: 

~ # mkdir /usr/lib/erlang
~ # cd /usr/lib/erlang
~ # tar xzvf /home/avr32/erlang-dist.tar.gz

Finally, create links to erl and erlc in /usr/bin: 

~ # ln -s /usr/lib/erlang/bin/erl /usr/bin/erl
~ # ln -s /usr/lib/erlang/bin/erlc /usr/bin/erlc

You may also wish to set up links in /usr/bin for dialyzer, typer and escript if you use those.

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