This weekend was the first 57N Stupid Shit No One Needs Hackathon . I tried this weekend to perform serial comms over a string and cup using the msp430 based TI Launchpad.

I had the tone generation working really quickly and then spent 15 hours trying to demod and tones and find a byte stream using a microphone. I had no chance, it didn't work at all.

I was able to transmit the tone a long the string over 3 meters of room. So the core idea does work. I think I will try this project again after reading some more dsp.

Hibby and I were happy to announce the first 57N Stupid Shit No One Needs Hackathon this week. It isn't often that you come across a strange link in your search history and it turns into an awesome event, we seem to have beaten the odds.

The first Stupid hackathon I read about produced some of the coolest ideas for pointless things I have ever seen. The best one to make the event clear has to be endless.horse .

So what are you going to do Tom?

Of the many terrible ideas I have each day, only a few are worth spending 48 hours polishing to death. This coming weekend I have decided to take two technologies I have been gradually learning, mirco controllers and DSP, and build the most terrifyingly bad things I can think of.

So tomorrow prepare yourself to see the start of a paper cup and string telegraph being forged in 57North Hacklab.

Just before I left work yesterday I built one of the gimme boards I got earlier this week and connected it up to a goodfet . I had to do a little source editing to let the goodfet run and connect to the correct serial port. If you need to change the serial port from the default it is a quick grep through the source tree to find literal string "/dev/ttyU0" to change.

I followed the instructions on the git repo for the specan code . The first time I ran the flasher the IM-ME booted into the stock firmware again. I erased the flash, tried again and it all worked. I am not sure how long the flashing took, but if you will be holding gimmme expect it to be a few minutes.

To flash the IM-ME I did:

$ goodfet.cc erase
$ goodfet.cc flash specan.hex

This turned out to be a lot easier than I expected, everything seems to be well documented. If you can get an IM-ME and want to flash it with a goodfet and a gimme, send me an email and I will send you one of my spare(partially assembled) boards.

My Yardstick One appeared yesterday, time to set up RFCat.

RFCat has not yet been packaged on FreeBSD so I had to install it manually. I pulled the RFCat source from bitbucket which includes both the firmware and the client tools. To play with the stock firmware on the YSO I just had to install the client tools.

The client tools depends on libusb-1.0 , which ships in FreeBSD and on pyusb . Pyusb is offered by the py27-usb port.

$ sudo pkg install py27-usb

Then I built the rfcat client tools:

$ cd code
$ hg clone ssh://hg@bitbucket.org/atlas0fd00m/rfcat
$ cd rfcat
$ sudo python setup.py install

I had to set up devfs rules to access the usb devices, with my account in the usb group I have the following:

# /etc/devfs.rules
[localrules=10]
add path 'usb/*' mode 0660 group usb 

#/etc/rc.conf
devfs_system_ruleset="localrules"
devd_enable="YES"

With that all set up I can now try the rfcat tools

$ rfcat -r
'RfCat, the greatest thing since Frequency Hopping!'

Research Mode: enjoy the raw power of rflib

currently your environment has an object called "d" for dongle.  this is how 
you interact with the rfcat dongle:
    >>> d.ping()
    >>> d.setFreq(433000000)
    >>> d.setMdmModulation(MOD_ASK_OOK)
    >>> d.makePktFLEN(250)
    >>> d.RFxmit("HALLO")
    >>> d.RFrecv()
    >>> print d.reprRadioConfig()

The r flag tells the client to throw me into the research prompt and I get left in something that looks sufficiently like ipython. To test that everything was working I decided to transmit some bytes in a loop in the ism 433 band.

In [1]: d.setFreq(433920000)

In [2]: d.setMdmModulation(MOD_ASK_OOK)

In [3]: d.makePktFLEN(4)

In [4]: d.setMdmDRate(4800)

In [5]: for i in range(0,15):d.RFxmit('\xDE\xAD\xBE\xEF');

In [6]: for i in range(0,15):d.RFxmit('\xDE\xAD\xBE\xEF');

In [7]: quit()

I used an rtlsdr dongle and sdrtouch on my phone to get a quick demod of the spectrum and to see a waterfall. I tried this a few times, but I wasn't seeing the expected signal. Right off to the far right edge of the screen I was seeing a jump in strength, tuning around a bit while transmitting I eventually caught my burst packet. It seems that my rtl dongle is about 400KHz off the actual observed frequency.

With the launch of the yardstick one I remembered the im-me I bought earlier this year. Not wanting to risk destroying one of the last available im-me's in the world I decided to get pcbs made of Michael Ossmann's gimme .

I found a link to the OSH Park board page an ordered a small batch(3 boards) for less than £10. They came in about 3 weeks and seem to be reasonable quality, I will try them when my goodfet appears this week.