www.apertus.org: apertus° accepted for Google Summer of Code 2017
We are very proud to announce that apertus° has been accepted as a new mentoring organization for this year’s Google Summer of Code (GSoC). As only a small number of new organizations are allowed to join each year and the majority already in the program have been participating for many years, this is especially exciting. For anyone not familiar, GSoC is a program where students are paid to contribute to selected open source projects between June and August.
Project Overview apertus° GSoC Profile apertus° Idea List apertus° GSoC Mailinglist
FPGA Hackers wanted
Field Programmable Gate Arrays (FPGAs) and their embedded systems are...
GTA04 project halts GTA04A5 due to OMAP3 PoP soldering issues
For those of you who don't know what the tinkerphones/OpenPhoenux GTA04 is: It is a 'professional hobbyist' hardware project (with at least public schematics, even if not open hardware in the sense that editable schematics and PCB design files are published) creating updated mainboards that can be used to upgrade Openmoko phones. They fit into the same enclosure and can use the same display/speaker/microphone.
What the GTA04 guys have been doing for many years is close to a miracle anyway: Trying to build a modern-day smartphone in low quantities, using off-the-shelf components available in those low quantities, and without a large company with its associated financial backing.
Smartphones...
Diodes part 3: a working diode steering circuit
I've made something interesting with my aluminium and soda bicarb diodes: a 7-segment display encoder. Also includes instructions on how to make your own.
Kalman filter
In few projects I've needed the Kalman filter to suppress the noise and other inaccuracies especially from accelerometers. Below is a nice picture from a live stream of data transmitted by the ESP8266 LDR over websockets to an application server written in javascript. The data received in the browser looks like:
With red is raw data and with white is the predicted data after the Kalman filter was applied.
IoT with ESP8266
Inside of a 1000lx bulb LED
Since this Livarno bulb refused to work after few months of fine operation I decided to dismount it.
Power supply was covered in rubber and it take a while to clean it between the components.
32 LEDs are used for this bulb. I've tested few of them with a 5V power supply and are very bright (don't look at them since is not a nice feeling after that)
Here is the power supply. Still has rubber left between components.
IoT with ESP8266
Manual testing of Linux Kernel GTP module
In May 2016 we got the GTP-U tunnel encapsulation/decapsulation module developed by Pablo Neira, Andreas Schultz and myself merged into the 4.8.0 mainline kernel.
During the second half of 2016, the code basically stayed untouched. In early 2017, several patch series of (at least) three authors have been published on the netdev mailing list for review and merge.
This poses the very valid question on how do we test those (sometimes quite intrusive) changes. Setting up a complete cellular network with either GPRS/EGPRS or even UMTS/HSPA is possible using OsmoSGSN and related Osmocom components. But it's of course a luxury that not many Linux kernel networking hackers...
www.apertus.org: AXIOM Team Talk Volume 12.2
https://invidious.privacyredirect.com/watch?v=MvFgHYnl3gg
Small Hardware Changes/Upgrades here and there
In this team talk, Sebastian gives a brief rundown of some recent hardware changes to the AXIOM Beta development kits. Changes include; different chips to reduce the Lattice FPGA programming time, a new connector to attach the main cooling fan (which is now held in place by noise reducing nylon screws), some schematic changes relating to the JTAG interface FTDI chips (to reduce power feedback), a new onboard sound buzzer. Also, to reduce mechanical stress on the electronics, we now have new precision manufactured nylon spacers to align the PCB stack at exactly the right...
Cellular re-broadcast over satellite
I've recently attended a seminar that (among other topics) also covered RF interference hunting. The speaker was talking about various real-world cases of RF interference and illustrating them in detail.
Of course everyone who has any interest in RF or cellular will know about fundamental issues of radio frequency interference. To the biggest part, you have
cells of the same operator interfering with each other due to too frequent frequency re-use, adjacent channel interference, etc.
cells of different operators interfering with each other due to intermodulation products and the like
cells interfering with cable TV, terrestrial TV
DECT interfering with cells
cells or microwave links interfering with SAT-TV reception
all types...
Towards a real SIGTRAN/SS7 stack in libosmo-sigtran
In the good old days ever since the late 1980ies - and a surprising amount even still today - telecom signaling traffic is still carried over circuit-switched SS7 with its TDM lines as physical layer, and not an IP/Ethernet based transport.
When Holger first created OsmoBSC, the BSC-only version of OpenBSC some 7-8 years ago, he needed to implement a minimal subset of SCCP wrapped in TCP called SCCP Lite. This was due to the simple fact that the MSC to which it should operate implemented this non-standard protocol stacking that was developed + deployed before the IETF SIGTRAN WG specified M3UA or SUA came around. But...
Testing (not only) telecom protocols
When implementing any kind of communication protocol, one always dreams of some existing test suite that one can simply run against the implementation to check if it performs correct in at least those use cases that matter to the given application.
Of course in the real world, there rarely are protocols where this is true. If test specifications exist at all, they are often just very abstract texts for human consumption that you as the reader should implement yourself.
For some (by far not all) of the protocols found in cellular networks, every so often I have seen some formal/abstract machine-parseable test specifications. Sometimes it was TTCN-2, and...