1) Configure SPI and enable a pullup for the IRQ pin in the mini2440 kernel.

2) Modify the spidev module to expose the IRQ using the userspace I/O system.

3) Write new SPI functions to interface between the radio and Neil’s driver.

4) Write a threaded interrupt handler to deal with the IRQ from the radio.

6) Port the driver to an ATmega16 development board and configure this as a receiver for testing.

5) Write a user space program to configure the radio as a transmitter and transmit a test message to the ATmega16 dev board.

We used the following development environment:

..and here are the modules on the dev boards:

The code for all of this (alpha at best) is available here:

https://github.com/dougszumski/nRF24L01

The next stage is to improve the speed of the driver. We currently estimate a maximum bandwidth of ~10B/s with jiffies set to 1000 which is a fraction of the true potential. One of the ideas so far is to move the SPI routines, the chip enable toggling and the interrupt handling back into the kernel, and then interface with something like a netlink socket. If anyone has any helpful advice we’d be pleased to hear from you.

More details will be posted on our forthcoming website which is TBA.

If you’re using BusError’s original repo then follow the OE instructions as normal, then you can use this guide if you want. As mentioned you’ll need to downgrade patch. I also had to downgrade make due to some incompatibility.

At first i had some error about the GPG key so i downloaded them for F13 and F12 from here. You can install them like this, for example:

Then, you’re good to bake.

If you want something bleeding edge you’ll need to get your hands dirty, OE has changed a lot recently!

…and here’s the finished product! The LED is 10mm diffuse with a common anode and a maximum current rating of 20mA per channel.  As soon as i’d soldered the wires to the CAT3626 i glued it to the board with epoxy, threaded the wires through the holes and then glued those down with more epoxy. After that i realised i’d forgotten where pin 1 had gone so i had to scrape the glue off the top of the chip!

The wire coming through the hole in the middle of this picture is soldered to the CAT3626 and acts as a crude heat sink. In practice it seems to work well enough although i probably should have used copper. I pulled the ceramics from an old projector i had lying around. Not the neatest job but it works fine!

After I’d built that i tested it quickly using I2C tools and then wrote a kernel driver.  The CAT3626 allows a maximum of 32mA per channel regulated in steps of 0.5mA. Unfortunately because my LED can take a maximum of 20mA per channel i can only generate ~64,000 colours. To make matters worse the light intensity is not in general a linear function of the input current so the achievable fade sequences are not as nice as those done with PWM but they still look pretty good. Here’s a video!

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]]> http://www.electronics.diycinema.co.uk/embedded/mini2440/cat3626-rgb-led-driver-qt-embedded-4-6-on-the-mini2440/feed/ 10 http://www.electronics.diycinema.co.uk/embedded/mini2440/chameleon-135-for-the-mini2440/ http://www.electronics.diycinema.co.uk/embedded/mini2440/chameleon-135-for-the-mini2440/#comments Sun, 28 Mar 2010 22:21:51 +0000 Doug http://www.electronics.diycinema.co.uk/?p=227 Thanks to www.andahammer.com both Will and I now have the Chameleon 135 enclosure for the Mini2440.  I’ve been working on a li-ion charger and once that’s finished we should be ready for some field testing. It takes a little while to get the holes drilled in the right place but once it’s screwed together the case is extremely sturdy. There’s loads of room inside for additional wiring

You can get the Chameleon from www.andahammer.com.

The chip is a Conwise CW6626. Anyway, what matters most is that if you have bluetooth configured it works out of the box!

Connecting to the GPS is easy. First check the interface:

If it says down bring it up:

After executing the above I got the following:

Now turn your GPS on and do a scan:

Now fill in /etc/bluetooth/rfcomm.conf with the details. Here’s mine:

Next bind the device:

And check the device output using:

Next i bitbaked gpsd, by simply typing:

In my OE installation (see the various posts about setting this up).

Once this builds you can install the appropriate ipks. From memory I think i installed the following:

This pulled in a whole load of other packages. Next you can start gpsd by typing:

And monitor the output using:

If all has gone well you should get a text output of the parsed NMEA data:

Anyway..that’s just the tip of the iceburg. If you want to learn more have a look at the gpsd website and the bluetooth page i have based this post on.

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On a fresh copy of Fedora 11 I updated the system and installed the packages reccommended by OE:

I then made a folder called OE in my home directory and git cloned the mini2440 repo:

I then setup the source-me.txt similar to before:

I put the following in:

Now all you need to do is setup the local.conf. Simply edit the example and copy it to the right place:

Read this file and edit as appropriate. I have attached mine as an example. Now copy it to the conf/local.conf

If you want qt4-embedded or any other package included in the build simply edit the recipe in:

I added qt4-embedded:

Then all you have to do is source the script from wherever you put it:

and run bitbake:

from the ~/OE/openembedded/ directory..

If you get an error trying to build a package try cleaning it:

Then try and build the image again. Maybe you won’t have this problem. I guess it’s either because the checksum parser failed to build or my hdd is dodgy. It only happened once on binutils but worked fine after cleaning it.

A few hours later if all goes well you should have images in:

Obviously that directory depends on what you setup in the local.conf.

Good luck!

First off I’d like to point out that this article is essentially an amalgamation of the Open Embedded Wiki (Getting Started) and Angstrom’s ‘Building Angstrom’ articles but in context relating to the mini2440 Embedded PC. If you would like a more detailed and probably better written explanation please refer to these two articles.

Make sure you have the packages needed for Open Embedded(OE) by visiting here and looking under the section relating to your distro. Running fedora 11 I did:

Getting down to business…

Open up a terminal. Issue these commands:

Download latest bitbake from here and extract the bitbake directory in the archive (eg. bitbake-1.8.16) to /stuff2/

A few more commands:

Edit the config you have just copied using your favourite text editor.

It is important that you read the config carefully so that you understand what everything does…

Next edit it to look something like this (which is just a slightly modified version of openembedded/contrib/angstrom/local.conf) :

Note: Do not copy and paste from this article due to formatting issues. You can download a pre-made local.conf here.Just extract to /stuff2/build/conf/ …

Save and exit the editor. Download this script and move it to the directory /stuff2/ .

Check it is ok:

It should look something like this:

save, and start the script:

one last update:

Issue a few commands to fix build issues:

issue build commands:

Be prepared to saturate your internet connection, wait a long time and take up a lot of disk space!
The result ends up in:

You should have the image(s) in .jffs2 for flashing and .tar.gz for mounting using NFS.

I quickly knocked together a circuit on veroboard and hooked up the base of a transistor to the freefall / motion interrupt pin to check it was working. It is remarkably sensitive, the LED flicks on if i drop my pen at one end of my desk when the device is at the other! I was quite pleased that everything was working well so i hooked it up to the I2C bus using the cable kit kindly supplied by www.andahammer.com. Using I2C tools i was able to set registers and read acceleration vectors without any trouble so i’m pretty sure everything is working well. I was a bit worried about exceeding the bus capacitance at first.

It turns out that i can still use the old device if i rely on the internal low pass filter. I was thinking of doing this anyway and using a Kalman filter to process the output. First i need to write a device driver so i’ve rapidly being trying to learn C. So far i’ve got a very basic kernel module up and running on the mini2440

To update the OE metadata simply:

Now make the suggested script source-me.txt changing OETREE to suit your needs:

I also had to set:

Then setup local.conf:

Now edit ${OETREE}/build/conf/local.conf and add this to the end:

Now download the mini2440 config file from openembedded. Put this in:

Now source the source-me.txt, go to the OE tree, check it’s up to date

Now build the images, you can build all of them or just one. I used the base image for running Qt but i also built the gpe image which worked nicely if you need it.

Be prepared to saturate your internet connection, wait a long time and take up a lot of disk space!

The result ends up in:

You should have the image(s) in .jffs2 for flashing and .tar.gz for mounting using NFS.