Raspberry Pi XBee PCBs

Picture of XBee PCBs

During the course of this week, I have received my XBee PCBs (right) and started playing with them!

First of all, I’d like to say thanks to the folks at Seeed Studio / Fusion PCB whose service I used to fab these boards. I went for the slightly more expensive ENIG finish on these, but they were still very reasonably priced and have come out very well indeed. I would definitely use them again.

So anyway, after a quick order for some extra TC2117 regulators that I found I ran out of, and a fistful of LEDs and that sort of thing, I built two backpacks up complete with XBee modules and set out to get them to talk. This was my first foray into the world of XBee / ZigBee so was a very interesting process!

XBee Backpacks on my two Raspberry Pis

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Raspberry Pi 3.2.23 kernel

Sorry folks, this one was late. So late that I completely skipped 3.2.22. Oh well, here it is at long last. Enjoy! I hope to publish a slightly revised version compiled with a new compiler and a few extra patches later this week, so keep your eyes peeled.

This one has a few additional changes on top of just the 3.2.23 update:

  • Enabled some more modules by popular request.
  • Included some further patches from the official kernel tree.
  • Compiled with Linaro GCC 2012.04 (thanks to crosstool-ng). I hope to use 2012.07 later this week for an updated kernel.
  • Fixed a minor sched_clock bug that printed a harmless warning at boot time.

Please see my kernel project page for download links and instructions.

New Revision of 3.2.21

I’ve posted a slightly updated 3.2.21 kernel. This includes the following updates:

  • Applied the GPIO interrupt patches from the official kernel (thanks Selsinork for the rebased pull request ready for applying to my tree!)
  • Enabled DVB modules and some more V4L modules related to this. Sorry, I thought this was all enabled previously.
  • Added DRBD module by request.


Updated Debian Wheezy Image

I updated my Minimal Debian Wheezy image for Raspberry Pi last weekend, but completely forgot to write about it. This includes my 3.2.21-r1 kernel and all the latest firmware and Debian package updates as of the 23rd.

Download: wheezy-mini-2012-06-23.img.gz (124M)

Once again the SSH server is not installed by default, so you will need to login using the console first either on an HDMI display with a USB keyboard or over the serial console.

The root password for this image is: raspberrypi

Raspberry Pi 3.2.21 kernel

You know the drill! A few days ago, Linux 3.2.21 was released. As usual I’ve updated my Raspberry Pi kernel. This one has a few additional changes on top of just the 3.2.20 to 3.2.21 update:

  • Imported some further patches from the official Raspberry Pi kernel, including some patches to the ALSA audio driver.

Please see my kernel project page for download links and instructions.

Raspberry Pi XBee SMT backpack

RPi-XBee-SMT Board

One of the earliest motivations for my work on the Raspberry Pi SPI driver was so that I could use some Digi XBee ZB SMT modules. These are basically the same as the normal XBee ZB modules for doing ZigBee with but are on little PCBs that you solder onto a carrier board—and they can speak SPI to the host processor instead of serial. I got several of these modules for a previous project that never materialised but the Raspberry Pi seems like a nice environment to have a play with these.

So I went ahead and designed a carrier PCB to hook these up to the Raspberry Pi’s GPIO expansion connector. You can see an Eagle exported image of the PCB to the right. It carries the XBee ZB SMT along with a bunch of LEDs and its own 3.3V LDO so it doesn’t draw too much from the Pi itself. I also threw in two FTDI connectors, one for the Raspberry Pi’s UART and one for the XBee module’s. It also sports a set of holes for the normal XBee modules (2mm headers) so you can use those as well over serial, but obviously you won’t be able to use SPI with those.

RPi-XBee-SMT Schematic

You can find the source Eagle files along with the associated libraries over in my RPi-XBee-SMT Git repo at GitHub. I’ve decided to release this under a Creative Commons Attribution-ShareAlike 2.0 UK: England & Wales License, making it Open Source Hardware (OSHW).

I haven’t yet ordered any PCBs of this, so I haven’t actually tried it out yet. If you have any comments on the schematic or layout then please let me know. I’ll try to get some ordered in the next couple of weeks – if you live in the UK and would like some yourself it may be worth pooling the order to get the price down so please comment / email if that’s the case.

Once I have some hardware to test with, the next step will be writing some drivers…

Raspberry Pi 3.2.20 Kernel

A few days ago, Linux 3.2.20 was released. As usual I’ve updated my Raspberry Pi kernel. This one has a few additional changes on top of just the 3.2.19 to 3.2.20 update:

  • Introduced some new SDHCI performance tweaks. These are also in the official kernel from the Raspberry Pi Foundation. These require the latest firmware or the kernel will not boot.
  • Added the easycap module.

Please see my kernel project page for download links and instructions.

Why I won’t support a 3.1 kernel

Copied from my Raspberry Pi kernel page:

One of the reasons I’m really pushing at a 3.2 kernel for the base image of the Raspberry Pi (until we get the architecture code rewritten for a mainline merge, another effort I’m part of) is that 3.1 is no longer an actively supported branch of the kernel and has some nasty security issues, whereas 3.2 is actively supported as it is the basis of Ubuntu 12.04 LTS (Precise Pangolin) and will be the kernel used in Debian Wheezy as well.

Please see Issue #2 on the Raspberry Pi kernel tree on GitHub for a fright. Here’s a technical description of the issue, including an exploit (linked from the GitHub issue).

In other words, 3.1.9 has nasty security holes that will come back to bite you. 3.2 is a long-term supported branch and really isn’t a big step to take from 3.1. So please, follow my lead and ditch the official Raspberry Pi 3.1.9 kernel and use something a bit more recent.

This means that I will not support the porting of my SPI and I2C drivers to the official kernel until it moves to 3.2 or a more recent branch. Such an effort would undoubtedly be very simple for whoever decides to undertake it, but it’s not something I am willing to help with. Sorry!

I am, however, most willing to help bring the official kernel to 3.2 or newer. After all, this is what I have already done.

Yet another new kernel – 3.2.19

A few days ago, Linux 3.2.19 was released. As usual I’ve updated my Raspberry Pi kernel. This one has a few additional changes on top of just the 3.2.18 to 3.2.19 update:

  • Reverted a problematic SDHCI patch that broke SD card access for lots of people.
  • Added lots of USB webcam modules.
  • Added some USB wifi adapter modules from the kernel staging directory.

As I seem to be doing this quite often and my kernels are becoming quite popular, I thought it best to give them their own project page. This means the link to the page will stay the same for every revision.

Grab your freshly baked Raspberry Pi 3.2.19 kernel today!

Slightly updated RPi kernel

I’ve updated my Raspberry Pi 3.2.18 kernel with some patches and slight configuration changes since the last one:

  • The USB code is now built-in instead of being a module. This means that people who want to keep their root filesystem on a USB hard disk or similar can do so.
  • Some fixes for my I2C driver that prevent it reading/writing further than it should have. This caused at least one user to experience a kernel panic.

I have not yet reverted the MMC/SD commit that I suspect is causing many people issues. So far I have had only one conclusive report that it has helped. If you have had trouble with an SD card in my kernel but not in the official kernel and have the opportunity to build a kernel with commit 84045e4 reverted, please let me know the outcome.

Update: This is no longer the most current kernel. You can find the latest version on my Raspberry Pi kernel project page.