So I just got VDSL, yay! Actually it’s more of a nay, given that it’s slower than the ADSL I used to have. While my ISP is supposedly busy analysing the problem, I have utilised my modified direct sampling RTL2832 to visualise what’s happening during the VDSL sync/handshake. (Using just a piece of wire taped along the phone line)
For quite a while I felt like I missed out while my colleagues were competing in a fun little game called Blobby Volley 2. While the game itself is actually open source software, I wasn’t able to find any build for OS X. So I took the Linux version of the source code and ported it over to OS X. In addition I’ve also come up with an icon of higher resolution since the default one wasn’t up to par.
Source code on github: https://github.com/EliasOenal/blobby
You get around the Apple Gatekeeper warning by right-clicking “Blobby Volley 2″ and selecting “Open”.
(Showing off the timing detection capabilities. Only the first few characters are wrongfully decoded while adjusting from 24WPM to 12WPM.)
Two weeks ago I thought writing a morse (aka CW) decoder would be a fun weekend project, and so I did it. As an additional challenge I decided to only rely on integer math, which forced me to rewrite core parts of multimon-ng. The resulting decoder also has basic threshold detection, as well as the ability to automatically adjust the timing. Note that there are several new parameters to adjust these options. In preparation for a morse encoder which I might write as well, I’ve revived multimon’s counterpart “gen” and gave it a nice qmake-file called “gen-ng.pro”. Building it works analog to multimon-ng.
Get it at GitHub: https://github.com/EliasOenal/multimon-ng
The CW decoder has a bunch of parameters worth tweaking. Also make sure to bandpass the signal as closely as possible. If you plan on using it, have a look at Matt’s blog: Matt’s RF Stuff
(I just felt like my low pass implementation was quite decorative.)
Given that Pandora is being Nazi about people’s backgrounds, (Or rather their IPs) I haven’t been able to use the service so far. Today though, I decided to hide behind a proxy and have a look at their offer. My client of choice was pianobar which is really lightweight, yet loaded with all of the features you could ever need – all but one, that is. Inspired by an older patch that sadly stopped working, I’ve added a feature that utilizes curl to download your favorite music. It integrates with pianobar’s history, meaning that you can fetch songs even after they’ve stopped playing. https://github.com/EliasOenal/pianobar
The only downside I found is their actual service: you only get 64kbps for free. While their prices seem quite reasonable, paying isn’t an option for me. Given that I’m in Germany and they don’t own the distribution rights over here, they couldn’t legally license the content to me – even if they wanted to.
If you’re in need of a proxy to use Pandora, look no further! I’ve used the mediahint.com Chrome extension to sign up and then used their proxy for pianobar as well. Just grab their configuration file from here: https://mediahint.com/default.pac (The IPs are represented as 32bit numbers)
In addition to downloading songs from Pandora, my branch now also supports replaying previous songs, as well as restarting playback for the currently playing one.
Some time ago I’ve tried the HF Mod (aka Direct Sampling Mod) on one of my dongles. The simplest way of doing it is by connecting one of the RTL2832U’s ADC (pin 1 or 2) inputs to an antenna which is exactly how I started. Shortly after that mikikg told me about using a transformer in order to generate a differential signal for the ADCs differential input, as well as boosting the signal and matching impedance. As a quick and dirty solution I desoldered a H16105DF 10/100Mbps Ethernet decoupling transformer from an old ADSL modem and used it. It actually matches the frequencies we care about quite well and in addition serves as a low pass filter. At the moment it is used in a 1:1 configuration, though 1:2 will probably perform better, thus I plan to try that as well. Using it together with an antenna made from a few meters of litz I receive many AM radio stations as well as lots of other signals.
Since someone over at reddit claimed that mikikg originally came up with using Ethernet transformers for the mod, implying I wouldn’t credit him properly, I feel like clarifying. On 10/3/12 I sent him a mail explaining that I had tried a variation of the HF-Mod using an Ethernet transformer and that the results were promising, I also attached a picture to that mail. Seemingly we then both blogged about it quite a while later, yet he did so before I did.
I have tried using the transformer in a 1:2 configuration and the signal actually got worse. That makes me wonder about the RTL2832U’s input impedance.
Recently one of the four drives in my HTPC kept dropping out, first it happened once every few days, then after several hours. The weird thing was that it always came back after losing the SATA link and allowed me to mount it again. I first thought it was a problem of the SATA controller or cables so I switched the drives around, yet the same drive was still affected. I then assumed it was related to the drive which got me sidetracked for a while, till I routinely decided to reset the BIOS. Doing so I randomly had a look at the supply voltages, the 12V rail had dropped to around 10.2V.
Gladly I had a spare ATX PSU which I then switched in resolving all the problems. The PSU that failed was a one hung low 75W high efficiency one that came with a miniITX case I bought a while ago. It consists of a AC/DC power brick supplying 12V and a DC/DC switch mode board generating the whole variety of ATX voltages. Some of the DC/DC boards electrolytic capacitors were bulgy and I couldn’t even find a datasheet for their brand so I decided to replace them all with fresh low ESR ones. Needless to say that solved the problem and it now works fine (11.83V) again.
It really was an annoying experience and the symptoms were highly misleading. After all the drive was fine, and it was just the manifestation of a completely different problem. From now on I will routinely check lm-sensors for voltages as well.
TNT stands for Thumb2 Newlib Toolchain, a GCC/Newlib based toolchain project I started quite a while ago. Trying various other toolchains like CodeSourcery, summon-arm-toolchain and YAGARTO, I realized none of them really seemed to have the smallest ARM Cortex-M microcontrollers in mind; They were wasteful with RAM as well as flash memory. TNT has been optimized for small unhosted (bare-metal) microcontroller targets and thus size optimizations have been the primary goal. Especially the C-library Newlib has been configured for the least possible size which makes using it (e.g. printf()) much more affordable. I have seen size reductions of over 30% compared to other GCC based toolchains when compiling the TNT_Example project.
The following architectures are supported:
armv6s-m (cortex-m0/cortex-m1) armv7-m (cortex-m3) armv7e-m (cortex-m4/cortex-m4f including FPU and DSP instruction support)
The TNT_Example project is targeted at beginners using STM32 microcontrollers, it plays well with TNT and other GCC based toolchains. It has an example on how to implement the Newlib stubs to get syscalls like malloc() and printf() working. For the STM32F4 discovery board you can just compile it and get the lights blinking. For other targets you’ll have to slightly adjust the makefile. https://github.com/EliasOenal/TNT_Example
A while ago I already managed to compile gqrx on OS X, but then Alexandru Csete decided to move on to a new audio backend called pulseaudio. Sadly there is no proper pulseaudio port for OS X. Thus I bring you my branch of gqrx 2.1 which runs quite well on OS X.
This release bundles all the rtl-sdr, gr-osmosdr, GNU Radio, libUSB, boost and Qt dependencies allowing it to work out of the box. Though feel free to contact me in case you encounter problems. It has been reported to run fine on Snow Leopard (10.6), OS X Lion (10.7), OS X Mountain Lion (10.8) and OS X Mavericks (10.9). Sadly Leopard (10.5) isn’t supported due to Apple breaking binary compatibility on 64bit binaries for some reason.
Download the ready to use DMG/APP here:
gqrx_8.dmg – (07/01/2013) Latest GIT. Some people are reporting FFT issues with this build, in case you encounter those try the one below and leave a comment.
gqrx_7.dmg – (02/03/2013) Up to date with GIT. I’ve added a deadlock prevention feature in case your settings keep gqrx from starting up properly. After a crash/forced-close it asks you whether you want to reset all your settings to default. This should help you guys with invalid rtl_tcp settings and the like. I have also fixed rtl_fm to now properly work on OS X (It used to only output noise), as well as multimonNG which now supports umlauts for POCSAG decoding. So check out the bundled command-line utilities! (e.g. /Applications/Gqrx.app/Contents/MacOS/rtl_test -t)
Continue reading ‘OS X port of the awesome gqrx SDR software [Update 07/01/2013]’ »
Qt has a great tool for building self contained application bundles on OSX, it’s called “macdeployqt”. Though I recently had a really weird bug while using it. When I ran the application normally everything was fine, but once I used the macdeployqt all the icons were missing. After a while investigating this I realized not all types of icons were affected, SVGs wouldn’t show, yet JPGs would. Long story short, you have to explicitly declare the use of the SVG module (or any other module you use) inside the project file so it ends up in the final bundle.
QT += svg
Due to my recent acquisition of an RTL-SDR compatible radio module (Some would call it DVB-T stick) I started playing with radio transmissions. Doing so I found POCSAG (pager) transmissions which I tried to decode using multimon. Sadly multimon was very broken, after I finally managed to compile it on OS X I realized it had 64bit bugs preventing the decoding on my system. So I forked it and patched a lot. I rewrote large parts of the POCSAG decoder after reading the patent text as well as implemented the BCH forward error correction. Besides improving POCSAG my main focus was portability, it now even compiles on Windows
MultimonNG a fork of multimon. It decodes the following digital transmission modes:
POCSAG512 POCSAG1200 POCSAG2400 EAS UFSK1200 CLIPFSK AFSK1200 AFSK2400 AFSK2400_2 AFSK2400_3 HAPN4800 FSK9600 DTMF ZVEI
The following changes have been made so far:
-Fixes for x64
-Basic functionality on Mac OS X ‘Lion’ (Soundcard/OSS input is unsupported)
-’DUMMY_AUDIO’ “backend” (Gets rid of the OSS dependency, breaks audio in doing so)
-’ONLY_RAW’ disables the format conversion while getting rid of posix dependencies
-Option ‘NO_X11′ to disable the X11 dependency since Apple will drop Xorg soon
-Override mode for POCSAG decoding (e.g. force text decoding)
-Brute-Force BCH implementation for POCSAG forward error correction
-Verbose mode is now listed in ‘-h’
-Merged Debian patches for EAS (Emergency Alert System) decoding (untested)
-Portability is a major goal
-Compiles on Windows (MinGW or Cygwin) without format conversion
-PulseAudio support, contributed by inf_l00p_
-Windows native audio and a VisualStudio/MSVC project file, contributed by bzzt_ploink
In addition to the deprecated legacy Makefile there is also a file for qmake which is the preferred way of building MultimonNG. It’s recommended to use qmake to generate the Makefile. (‘qmake multimonNG.pro && make’)
So far multimonNG has been successfully built on OS X, Debian, Ubuntu and Windows. (On Windows using the Qt-MinGW build environment, as well as Cygwin and VisualStudio/MSVC)
Files can be easily converted into multimonNGs native raw format using ‘sox’.
e.g. “sox -t wav infile.wav -esigned-integer -b16 -r 22050 -t raw outfile.raw remix 1″
GNURadio can also generate the format using the file sink in input mode ‘short’.
Windows version (Update 02/02/13 – Properly convert umlauts.): multimonNG_win32
(It doesn’t come with SoX and as a result can’t handle filetype conversions. Soundcard input and virtual audio cables should work fine, though.)
Some testfile converted to the native multimon format: poc1200
To decode it try “multimonNG.exe -a POCSAG1200 -t raw poc1200.raw”.
(“-i” is needed for recent versions of multimon-ng)
Superkuh wrote a bit about using multimonNG with GNURadio allowing for realtime decoding. http://superkuh.com/rtlsdr.html
Apparently you can combine multimonNG with rtl_fm to live decode POCSAG. It even seems to be lightweight enough to work on a Raspberry Pi. Thanks to Sonny_Jim from ##rtlsdr on freenode for trying!
<Sonny_Jim> Ok, so this works:
<Sonny_Jim> rtl_fm -f 153.353e6 -g 100 -s 22050 -l 310 – |multimon -t raw -a POCSAG1200 -f alpha /dev/stdin