Detecing LoRaWan traffic with SDR-RTL

RTL-SDR is a Software Defined Radio using a cheap DVB-T receiver with a chip from Realtek (RTL).

It can tune to 868 MHz and show activity, which is really handy when you are debugging a LoRa node and need to figure out if it is actually transmitting anything.

I bought the receiver from van Dijken Electronica at their stand at the VERON fleamarket for about 25 euro. It plugs into USB or a raspberry pi and the software is free (as in beer). I use SDR# from Airspy.

This is a couple of minutes traffic from a LoRa node building meetup.
The top graph is the current spectrum around 868 MHz, the lower graph is the history. The fuzzy red rectangles are spread spectrum LoRa transmissions.


Philips changes support for 3rd party lamps from Hue, twice.

It seems a firmware update for the Hue bridge and Hue bridge 2 has removed compatibility to 3rd party lamps, that version of the firmware will only work with “Friends of Hue” lamps and no longer support generic Zigbee Light Link lamps.

There was a lot of backlash on this as it can make existing, working, setups useless and raised questions about Philips still effectively being a  member of the  TCLA and if Hue bridges are still Zigbee complaint ?

So, Philips have announced they will (or have) reverse(d) the update on twitter and on meethue.

One sore point seems to remain : Apple HomeKit certification apparently not only applies to the Hue bridge but also to the lamps connected to the Hue Bridge :

Before the 1.11 software update, a bug in the Philips Hue system allowed some non-Apple HomeKit certified lights to work with Apple HomeKit. Our 1.11 software update removed the bug with the result that non-Apple HomeKit certified lights no longer work with Apple HomeKit. This remains the case.

(from meethue). Welcome to the long arm of Apple‘s Walled Garden.



The discovery and confirmation of the update that removed support :
iPhone-Ticker :
Meethue on Twitter :

The announcement of the reversal :
Meethue :
Twitter :

One years DX mail.


Among the stuff i bought is :
SKU: 382445 Quad band GPRS module. Haven’t played with this yet. There is no documentation on the DX page. Seeed has some general info about the module and the Seeed module that may be helpfull. The Adafruit FONA shield uses this module as well.The last picture in the DX page can be used to figure out the pin-out. One thing I did notice is that the board is not going to fit on a breadboard nicely.

SKU: 131727 and SKU: 131728 Pre-cut, stripped and tinned wires : sort and long. Preparing wires for soldering can be a drag. Just buy them ready to solder.

SKU:4711. Solder Paste (sold out). The name “Solder Paste” is a source of great confusion. This type is basically solder (so lead-tin-silver-whatever) in paste form. “Solder Paste” can also be flux to improve soldering and is a resin. Both are sold in very very similar looking jars described very poorly on DX.

SKU:19866 Stainless Steel Precision Angled Tweezers. These are by far my favorite tweezers for precision work. They fit nicely when closed and because they are in a 90 degree are great fro placing SMD parts.

SKU: 326247 10-pin female-female wires. Lots of prototype-able parts have pins but are not breadboard friendly. The female wires let you hook them up.

SKU: 146300: .   3W amplifier. Haven’t tried this but the idea was to use this with the MP3  module.

SKU: 221187  VS1003B MP3 Decoder. Breakout board for the VLSI VS1003. I have no idea why they mention the STM32. Haven’t played with this yet.

SKU: 149344ODBII -> bluetooth bridge. Lets you see what’s going on in the car diagnostics system. Works with Torque on the Nexus 7.

SKU: 331938 . One of the many Google Cardboard implementations . Useless to me as the Nexus 7 won’t fit.

SKU: 219245  Thin and flexible network cable. Works like a charm and uses little space.

SKU: 56648457 Anti-Static Static Charge Release Wrist Band (1.6M Grounding Cable). If you are working on repairing electronic equipment it’s smart to take precautions against static electricity. I have a mat as well and all the electric / electronic tools are grounded.

SKU: 268720 NILLKIN Protective Flip Open Case w/ Stand for Google Nexus 7 II – Black. The Nexus falls sometimes, coffee gets spilled, accidents happen. Then it is nice to have a case. The fake leather on the inside gets dirty. And i have no idea what “There is no end in pursuing.” means that is written on the inside.

SKU: 288552 Key Shaped Phillips Screwdriver + Slotted Screwdriver Set. Two screwdrivers to attach to your keychain.

SKU: 142041 FTDI Breakout board. Most embedded / hobby  stuff either has a USB serial serial on board (teensy, arduino etc.) or has a logic level serial interface. This FTDI breakout board provides you with a USB serial interface. Specs are thin, as usual on DX, but the board seems to use the “standard” pinout that Adafruit, FTDI, Sparkfun and JeeLabs use.


The price difference is pretty huge compared to the (about 6 USD vs 15 USD). I wonder if the FTDI chips on this board are the real deal. Also, it’s unclear how the board can be modified from 5 V. to 3.3V.

SKU: 223501 A Female to micro USB male. I have a couple of these to connect USB devices to a Nexus 7 via USB OTG. Nexus Media Importer will mount this external storage just fine. Great for watching movies while traveling or viewing the images on the camera.

SKU: 298972 RJ45 connector . Bought to be able to improvise a female RJ45 on a UTP cable. Never used them.

SKU: 56648457 Power plug converter. Many power supplies (safe ones from a proper brand) can work from 110 to 230 V AC. It’s just that they have the wrong plug. I prefer not to but you can use one of these plug converters to plug a US cable or adapter in a European socket. Check the maximum and minimum input voltages of the device you will connect.


ITead Studio Foca and RDM360-UART

Just in from China :

The ITead Studio Foca V2.1 USB to serial converter and the ITead Studio RDM360-UART 125kHz RFID tag reader.

FT232RL board with RDM630 RFID reader
FT232RL board with RDM630 RFID reader


Together with the female connector wires from DealExtreme you can quickly build a test setup and read 125kHz RFID tags.

One complication : The datasheet for the ITead Studio Foca V2.1 is WRONG !

The incorrect connection diagram of the ITead Studio FT232RL board..
The incorrect connection diagram of the ITead Studio FT232RL board..

The wiring diagram does not correspond with the board. The correct pinout is on the rear of the board, the wires goes on top. Strange and clumsy.

The rear of the actual ITead Studio FT232RL board.
The rear of the actual ITead Studio FT232RL board.

With the correct pinout the setup works like a charm.

Professor Layton puzzle and Wolfram Alpha

Professor Layton and the Unwound Future is a puzzle game for the Nintendo DS.

Puzzle number 40 is this :

The description is a bit unclear. What they seem to want is :

a * b = c + d


a + b = c * d

Plugging this in Wolfram Alpha as :

((a + b ) = (c * d)) and ((a * b) = (c + d)) and (a > 0) and (a < 10)

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