Active Antenna Reprogramming

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This page is about reprogramming the Active Antenna, which is a standalone version of the XO laptop's wireless mesh network interface.

Introduction

The Active Antenna performs two functions: it serves as a mesh interface for school servers, and it serves as a stand-alone mesh repeater. It was tension between these two functions that led to the pre-build and prototype builds to be manufactured with firmware which puts them into the mesh repeater mode before a server has had time to boot (Trac #4632). This page describes the recommended setup for reprogramming the firmware. It also describes how to "fix" an Active Antenna for use with a server, and how to upgrade the firmware on a mesh repeater.

Two older methods are documented for updating the Active Antenna. One, the Driver Method, requires replacing the drivers and works on XO laptops. Another, the User Space Method, requires that drivers for the antenna not be installed, and does not work with these instructions on XO laptops. These older methods are undesirable because they require manipulating the installed drivers. This page also describes a third way, the sysfs method, that is the recommended way to reprogram the active antenna.

Background on Active Antenna Firmware

Users may be slightly confused about which firmware images go where, why they go there, and what they do. This section provides a bit of background so that users upgrading the firmware can understand what, exactly, they are doing.

Boot2 is the bootloader that resides in the persistent memory of all mesh interfaces, whether built into the XO or in an Active Antenna. When the mesh device is powered on, Boot2 is the first thing to run. Older versions of Boot2 wait to be initialized by a USB host (e.g., the XO or school server), which will pass a firmware image that Boot2 will load and execute (i.e., the firmware image in /lib/firmware/usb8388.bin). This is the common behavior for the XO's built-in interface.

Newer versions of Boot2, such as those shipped on the Active Antenna, decide whether to load and run a firmware image from the USB host, or whether to load and run a firmware image that has been flashed to its persistent memory (i.e., stand-alone or mesh-repeater mode). They make this decision by waiting for a configurable amount of time to hear from a host (see Active Antenna Persistent Configuration), then booting the persistent firmware if it hears nothing. Note that this behavior does not apply to the XO's built-in wireless device. For one reason, these devices do not have persistent firmware. For another, they are always attached to a USB host because they are built in. For still another, they ship with older versions of Boot2 that unconditionally load firmware from a USB host.

So, when you update Boot2 as described below, you are simply writing a new Boot2 image to the persistent memory of the device. Every time the device is powered on, this version of Boot2 will run. Similarly, when flashing the firmware image, you are updating the firmware image in the device's persistent memory. This new firmware image will only run if Boot2 times out waiting for contact from a USB host.

What version of Boot2 and firmware is an Active Antenna running ?

You can determine which Boot2 firmware is currently on the Active Antenna or built-in wireless device using:

lsusb -v -d 1286:2001 | grep bcdDevice

The response should be something like "31.09" (indicating the shipped Boot2 version), "31.07" (indicating current boot-from-host-only Boot2), or "31.1A" (indicating current boot-stand-alone-or-host Boot2). If you get a response other than this, please contact server-devel at laptop.org as upgrading earlier versions (which shouldn't be encountered in the field) require additional steps.

lsusb is part of the usbutils package, which can be installed on an XO by typing:

yum install usbutils

Determining which version of the firmware an Active Antenna is running depends on whether it is plugged into a USB host or whether it is operating in "stand-alone/mesh-repeater" mode. In the former case, the firmware is loaded over USB by the host. You can determine the firmware version by typing:

ethtool -i ethX | grep firmware

This, of course, is simply the version of the firmware that is currently installed in /lib/firmware/usb8388.bin. In the latter case, you will need a sniffer to determine the firmware version. First, plug the Active Antenna into a host and check which channel it is configured to use:

cat /sys/class/net/ethX/boot_options/channel

While you're at it, note the MAC address of the Active Antenna using ifconfig. Now unplug the it and boot it as a stand-alone mesh repeater by applying 5v (i.e., NOT by plugging it into a USB host). Sniff on the proper channel for beacons with the Active Antenna's MAC address as the source. The beacon will contain the firmware version number.

How to upgrade the boot2 and the firmware in the Active Antennae?

Note: This is page describes the currently recommended method to upgrade both boot2 and firmware in the Active Antennae, which is based on the sysfs pseudo-filesystem. If you are interested in the older (unsupported) methods, they are documented in this page.

Required bits are committed to the testing branch of the olpc kernel tree. There is also at least two kernel RPM packages with the necessary changes to the Libertas driver already available. They are both based on the stable branch (so probably equivalent):

• http://dev.laptop.org/~dsaxena/kernel-2.6.22-20080722.1.olpc.0.i586.rpm
• http://dev.laptop.org/~rcarrano/kernel-2.6.22-20080721.1.olpc.0_carrano.i586.rpm

The firmware release 5.110.22.p17 supports the update of boot2, firmware, and persistent configuration of the Active Antenna and should be used in this procedure:

WARNING: Do not install version 31.1B of Boot2 with this method! This particular version of Boot2 has known problems.

• Install firmware 22.p17 in the host (by copying it to /lib/firmware with name usb8388.bin and then restart the XO or reload the usb8xxx module)
• Ensure that the images you wish to flash to the device are in /lib/firmware. In all likelihood, the firmware you wish to flash is simply the usb8388.bin that is already present. (Question: where does the boot2 image come from?)
• To update the boot2, execute:

echo <boot2_img> > /sys/class/net/<interface>/lbs_flash_boot2

• To update the firmware, execute:

echo usb8388.bin > /sys/class/net/<interface>/lbs_flash_fw

Note that if you try to use these methods on a built-in device, or with an older version of firmware, they will fail with a Not Supported error.

After you upgrade your active antenna, you might wish to set some persistent configuration parameters