Easy Wireless and Bluetooth for BeagleBoard-xM

May 29th, 2011 1 comment

Interested in adding wireless and Bluetooth capabilities to your BeagleBoard and BeagleBoard-xM? Well I found this BEAGLE WLAN ADAPTER at Board Zoo. I haven’t tried this product but it appears to be well documented, designed and the price is about $60. It attaches to the bottom of the BeagleBoard and extends out to the left so it shouldn’t get it the way of other expansion headers found on the BeagleBoard.

If you’ve used this product please let us know how it works.

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Progress! SPI is working on the BeagleBoard-xM

March 22nd, 2011 26 comments

As a first step to writing a Linux SPI device driver for the Maxim 7221 LED display driver chip I decided to at least prove that I can get SPI working on the BeagleBoard-xM with the BeagleBoard-xM Trainer Expansion Board which provides level translated SPI and GPIO pins.

To get this to work I had to do the following:

  1. Patch the Linux Kernel 2.6.32 BeagleBoard board specific arch/arm/mach-omap2/board-omap3beagle.c so that the SPI pins get configured correctly and the SPIDEV driver is made aware of the SPI devices on the board. For the patch information see this page.
  2. Once the kernel was patched I used the Angstrom distribution OpenEmbedded build environment to re-build the kernel.
  3. Build the spidev_test.c program that is part of the Documentation/spi tree in the linux kernel source using a cross compiler built using the crosstool-ng cross compiler build system.
  4. Load the spidev_test executable onto the Beagleboard-xM

With everything set up and ready to go it was time to boot BeagleBoard-xM and verify that the required SPI devices appeared in the /dev directory. Upon booting I was very happy to see the following:

root@beagleboard:/# ls /dev/spi*
/dev/spidev3.0 /dev/spidev3.1 /dev/spidev4.0

With the spidev devices being present it was time to see if they actually worked! So I hooked up my USBee SX logic analyzer to the Trainer boards McSPI4 pins and ran the spidev_test program. What the logic analyzer saw was exactly what the spidev_test program was sending! I’ve now verified that I can communicate with SPI devices using the kernels SPIDEV driver.

The spidev_test program sends the following data:

uint8_t tx[] = {
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0x40, 0x00, 0x00, 0x00, 0x00, 0x95,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xDE, 0xAD, 0xBE, 0xEF, 0xBA, 0xAD,
0xF0, 0x0D,

You can see from the following screen shot that the data was properly transmitted via the SPI:

Click the image to view full size.

And here are some images of the BeagleBoard-xM set up with the Trainer card and the USBee logic analyzer attached:

Click on image to see full size.


Click on image to see full size.


The next step is to write some code to put the SPI LED display through it’s paces.


Excellent Linux Device Driver Textbook

February 3rd, 2011 2 comments

Essential Linux Device DriversI haven’t written any Linux device drivers, only a few simple user space routines to access memory mapped hardware. Realizing that writing kernel device drivers is a complicated task I decided to find a textbook from which to learn. I’m currently reading through Essential Linux Device Drivers while I work on my LED display board driver project.

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First Project – SPI connected LED display board

January 31st, 2011 5 comments

I built an 8 digit 7 segment led display board based on a Maxim 7221 with SPI serial interface to a host processor and got it running rather nicely on an Olimex LPC-2138 (ARM7) based development board.

My plans are as follows:

  • Create a user space software to control the display board and then have it display things like load, uptime and debugging information by controlling each LED segment separately.
  • Then turn that user space board driver code into a Linux kernel module and modify the application code to user the driver interface.

This should be a fun and useful project. I will post progress reports. Wish me luck!

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My BeagleBoard-xM

January 30th, 2011 2 comments

To kick it off, here is an image of my Beagleboard-xM.

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So what is the BeagleBoard-xM?

January 30th, 2011 70 comments
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