Xenomai - Mini Howto

Xenomai

The following quick guide gives a rough overview how I got Adeos & Xenomai (real-time extension for Linux) running on the verdex.

Quick Install Guide

Step 1: Gumstix OE setup

At first, setup the build environment.

Note, that the step

$ cat gumstix-oe/extras/profile >> ~/.bashrc

defines environment variables - amongst others, it sets the directory for USERBRANCH which is used to provide our custom bitbake package.

Step 2: Custom Configuration

Download the user.collection to build Xenomai for Gumstix OE. Unpacking the file in the Gumstix OE root directory will give the following structure:

user.collection
user.collection/conf
user.collection/conf/machine
user.collection/conf/machine/include
user.collection/packages
user.collection/packages/xenomai
user.collection/packages/xenomai/xenomai-2.4.6
user.collection/packages/linux
user.collection/packages/linux/gumstix-xenomai-kernel-2.6.24
user.collection/packages/linux/gumstix-xenomai-kernel-2.6.24/gumstix-custom-verdex

Step 3: (Re-)build the kernel and system

$ bitbake gumstix-xenomai-kernel
$ bitbake -c rebuild task-base-gumstix
$ bitbake -c rebuild gumstix-basic-image

Step 4: Images

The kernel and root filesystem image can be found in tmp/deploy/glibc/images.

Troubleshooting

Xenomai for verdex with Qemu

It is also possible to run the real-time kernel within Qemu. However, it might be necessary to slow down the clock of the emulated system (Probably, as your host computer is too slow).

The following steps can help:

Alter the file hw/pxa2xx_timer.c in the Qemu sources:

1. Change all occurences of qemu_get_clock(vm_clock) to PXA2XX_QEMU_GET_CLOCK()

2. Define the macro

#define PXA2XX_QEMU_GET_CLOCK()     (qemu_get_clock(vm_clock) >> 4) /* also try 2,3 or use a divider */