Saturday, November 28, 2015

Acurite 592TXR Temperature and Humidity Sensors now decoded by rtl_433.

I've added decoding of Acurite's 592TXR "Tower" temperature and humidity sensors to rtl_433. These are small, inexpensive, wirelesss (433 Mhz), temperature and humidity sensors. The 592TXR has several different model numbers including 06002RM

These are compatible with Acurite's consoles such as the 01512 that I have as well as Acurite's Acu-Link Internet bridge which posts to acu-link's web page as well as weatherunderground. I picked up the Acurite 5-n-1 Weather Station, a console, and the internet bridge because the support for the 5-n-1 had been added to rtl_433 and the package price was pretty reasonable.

There were a number of people interested in decoding the 592TXR, but for some reason, it never got added, so I finally added it and cleaned up the Acurite 5-n-1 weather station decoding. The pull request got merged November 8th, 2015.

I think the temperature only version, the 592TX, should also be supported but I don't have one to test. Please let me know if it decodes successfully or not.

The protocol used by the Acurite 592TXR and the 5-n-1 weather station are very similar. The weather station's messages are one byte longer, but they are basically the same with the same RF signaling characteristics.

Remotely monitor Refrigerator / Freezer temperature with Acurite 986 and rtl_433 (rtl-sdr)

I suspected the thermostat in my basement refrigerator was going bad, so I picked up an Acurite 986 refrigerator and freezer remote thermometer.  The display unit will give alarms if the temperature goes out of range.

I wanted a better picture of what was going on so I figured out the Acurite's 433 mhz protocol for the 986 sensors. I've added support to rtl_433. The pull request was merged November 20th, 2015.

Now I pump the data into rrdtool and see what's going on. I now see how long and often the compressor is running, and how long it times to warm up between cycles. The spikes are the defrost cycles.

Now I can also monitor/get alerted when I'm out of the house.

I'm pretty happy with the Acurite 986 display and temperature sensors even without the rtl_433 decoding.

Acurite 00986 Refrigerator / Freezer Thermometer Protocol

  • Includes two sensors and a display, labeled 1 and 2, by default Sensor 1 - Refrigerator, 2 - Freezer.
  • Data format: Pulse Position Modulated (PPM), 5 bytes, sent twice, no gap between repeaters
  • Start/sync pulses: two short, with short gaps, followed by 4 long pulse/gaps.
  • Data Format - 5 bytes, sent LSB first, reversed
  • TT - Temperature in Fahrenehit
    • integer, 
    • MSB = sign. Encoding is "Sign and magnitude"
  • II - 16 bit sensor ID changes at each power up
  • SS - status/sensor type
    • 0x01 = Sensor 2 (
    • 0x02 = low battery
  • CC = CRC (CRC-8 polynomial 0x07, little-endian) 
I was able to easily figure out the CRC with CRC RevEng..

Friday, August 14, 2015

Another Yaesu VX-8DR external GPS with an Arduino/ATmega328 translator.

I've collected links for a few of these projects to add a better external GPS to the Yaesu VX-8DR, instead of the somewhat proprietary Yaesu option.

Here's another one from VK3YY that got posted recently:

Here's code from DFannin on github:
Update 2016-01-15, 4Z7DTF notified me about his project, which includes more additional analysis of how poor the VX-8's parsing and error handling is.

Background Info:

Good detailed blog post Reverse Engineering the Yaesu VX-8DR GPS Interface. From Feb. 2013. He didn't arrive at the solution, which I believe F4FXL and at least one other have. But I think he's got most of the relevant details for the padding differences listed as well as some other very useful info including details on the GPS chips used in VX-8 and VX-8G.

We now know how to connect to and send a properly formatted GPS NMEA message to the Yaesu VX-8DR. Here's the summary:
  • 9600baud TTL 3.3V serial signalling, 8/N/1
    • NOT RS232 -5 to +5V signalling -- you need a level converter if that's all you have
  • 3-wire physical interface to the following pins:
    Pin GPS Side Purpose Yaesu Side Purpose
    4 GPS RX Yaesu TX
    5 GPS TX Yaesu RX
    6 GPS GND Yaesu GND
  • According to 4Z7DTF (2016-01-15), there is no need for the communication to be bidirectional. Only the TX Data from the GPS to the VX-8 is required.

The messages need to be formatted exactly as follows:

Message Type Source Sentence
$GPGGA Sample $GPGGA,123223.000,4131.2334,N,00021.1216,E,1,04,02.7,00123.4,M,0051.7,M,000.0,0000*41

Syntax $GPGGA,hhmmss.sss,llll.llll,a,yyyyy.yyyy,a,x,xx,xx.x,xxxxx.x,M,xxxx.x,M,xxx.x,xxxx*hh
$GPRMC Sample $GPRMC,123223.000,A,4131.2334,N,00021.1216,E,0000.00,291.33,301011,,*3E

Syntax $GPRMC,hhmmss.sss,A,llll.llll,a,yyyyy.yyyy,a,xxxx.xx,xxx.xx,xxxxxx,,*hh
$GPZDA Sample $GPZDA,123223.000,30,10,2011,,*55

Syntax $GPZDA,hhmmss.sss,xx,xx,xxxx,,*hh

Thursday, August 6, 2015

rtl_433 now decodes DSC 433 Mhz wireless securty contacts

** UPDATE For status bit decoding see rtl_433 DSC Status Bit Decoding **

If you have a DSC (Digital Security Controls) home security system, with wireless sensors such as door / window contacts, glass break detectors, smoke, CO2, heat, and water detectors, you can now monitor them with rtl_433. The code is now in the mainline Merbanan github repo.

Only the 433 Mhz security sensors/contacts devices are currently supported.  I will be working on other devices soon. I have almost all of the status bits worked out. I will be submitting a pull request soon.

DSC alarm systems are also sold under other brands such as ADT Pulse, and a number of cable/telephone company's home automation systems, such as Time Warner Intelligent Home. DSC is a division of Tyco, so you will also see DSC products listed as Tyco Security, though Tyco has a whole list of security brands.

These are fairly inexpensive wireless devices that can also be useful for a variety of home automation projects.

The DSC WS4945 - Wireless Door and Window contact can be used as a magnetic contact or used with any sort of sensor that provides a normally closed output. If you are using it for home automation without a security system, it doesn't matter if it is normally closed or normally open. It will transmit at any state change. The device also sends a heartbeat with the current state every 64 minutes.

The Vanishing door/window contact, EV-DW4975 is quite thin and small if you don't need the screw terminals for wiring up some other type of sensor. It will barely be noticed on most doors and windows.

If you are interested in decoding DSC's wireless protocols, or have any information to share, please contact me, I could certainly use someone to collaborate with.

** UPDATE For status bit decoding see rtl_433 DSC Status Bit Decoding **

Popular Electronics Magazine archive online 1954 - 2003

A piece of electronics history:

Popular Electronics Magazine issues from 1954-2003 are available on line.  

Might be old news, but I just saw this circulating on a few mailing lists.

This is the first time I recall seeing a reference to this web site, American Radio History.

Popular Electronics was created in 1954 by Ziff-Davis Publishing for an audience of electronics hobbyists and experimenters. It soon became the "World's Largest-Selling Electronics Magazine". The circulation was 240,000 by 1957 and exceeded 400,000 by 1963. Rival Electronics World was merged into Popular Electronics in 1972.

Popular Electronics became Computers & Electronics in November 1982; and then ceased publication in April of 1985.

The title returned in February 1989 under the ownership of Gernsback Publications which purchased the name and gave it to their Hands-On Electronics magazine. Popular Electronics ceased publication in December of 1999, returning as Poptronics in January of 2000 after merging with Electronics Now. The final issue was  January, 2003.

Friday, April 17, 2015

New Toys: Getting Deeper into Software Defined Radio (SDR) (AirSpy and HackRF Blue)

This is mostly a tease / place holder.   Around Christmas time I decided to get deeper into Software Defined Radio (SDR).  So I ordered an Airspy and a Hack RF Blue.   So far, I've received the AirSpy and am enjoying it very much.  The Hack RF Blue should hopefully be here soon.

Previously I've been using the $15-20 RTL-SDR dongles.  These are very cheap and useful, but plagued with lots of noise, frequency inaccuracies and other problems.  Still they are a great way to get started and start learning.

The AirSpy is a world of difference from the RTL-SDR dongles.  One of the reasons that I bought it was  a number of people who seemed to have deep RF engineering backgrounds seemed to be pretty excited about it.  There are many good reviews available.

I ordered the HackRF Blue to experiment with GNU Radio and especially try some of the transmission capabilities for digital RF hacking.  Initially I'll probably be doing further experiments with simple 433 Mhz devices.

I expect based on receivers that the HackRF's receiver will not be as good as the AirSpy's by a good margin, for sensitivity, selectivity, etc.. However, the HackRF is capable of operating on a much wider frequency range (10 Mhz - 6 Ghz) than the R820T (24 Mhz - 1.8 Ghz) tuner chip inside the AirSpy.

More to come.

Your Radio's Reverse button / Quickiy Checking the Repeater's Input Frequency

[This was originally published on a mailing list, but seemed worth making more widely available.]

Some amateur radios have a "Reverse"(*) button that swaps the repeater input and output frequencies, allowing you to quickly monitor the repeater input and transmit on the repeater output.  When I first started out, I didn't realize the value of this.

The benefits of this feature are:

  • You can quickly listen to the repeater input to determine if someone transmitting is close enough for you to use simplex and free up the repeater.
  • If the repeater isn't working, you can get anyone who is monitoring the repeater's output and is within simplex range, to hear you by transmitting on the repeater's output.
  • During time of malicious interference or other search operation, if we all switch over to monitoring the input and make note of whether we can hear the transmitting station, we can use the information to figure out roughly what area the transmitting station is in.

And finally, the benefit that is relevant to the original topic, hitting the reverse button on many radios is a quick way of seeing what frequency your radio is programmed to transmit on for a repeater.  Your radio display will need to be in a mode to show the frequency rather than the label.

Check your radio's manual to find out how to activate the reverse feature as the button might have an obscure label.  A few common one:
  • Wouxun - It's the scan button.  (A quick press and release).
  • Baofeng UV-5 - The * button.  (A quick press and release). 
  • Many Yaesus - Home/Reverse, HM/RV, Rev, etc.

RTL-SDR Buying Tips

[This was originally posted to a mailing list.]

First, a good starting point on RTL-SDR is the blog site

(I've mentioned it here before and forwarded some relevant posts about things you can do with an SDR such as the RTL-SDR.)

The RTL-SDRs are almost all the same chinese, ultra cheaply made receivers in the range of $15-25.   It isn't so much about which device is trustworthy, it's what tuner chip does it have.

At this point, I suggest getting one with the R820T2 tuner which is newer, seems to perform a little bit better, but costs around $5 more than the others.  IF you get an R820T (not T2) that will do fine as well.

Places that "specialize" in RTL-SDR and aren't too overpriced are:

  • Nooelec,,  They also sell through Amazon.

    Their "NESDR Mini 2 SDR" was mentioned on the net $25.  It has the R820T2 tuner chip.  It's not clear if they upgraded any of the other components other than the included mini-whip antenna which you will probably replace.
  • is also selling their own branded R820T2 usb dongles.   They also sell through Amazon.  They claim upgraded components  and a better oscillator (though not temperature controlled) than the usual ones which can easily have a -75 to +75 PPM error.

At this point, almost all of the devices come with an MCX connector so you will need an MCX adapter to hook it up to a real antenna. Both NooElec and's amazon store have MCX adapters.

Also if you don't have any, get some USB extension cables (A male to A-female) around 10 ft in length.  These devices have no shielding, so you want to get them as far away from your computer as you can while sticking within USB length limits.

Try to get a good quality USB extension cable with a ferrite core near the end to cut some of the noise.  You might also want to buy some additional snap on ferrite cores.

Note: The frequency range on these is about 24 Mhz - 1,700 Mhz so you won't be able to do any HF with the exception of 10 meters and maybe 12 meters.  An upconverter can be used if you want to receive HF.

If you connect the RTL-SDR to an outdoor antenna, keep in mind that almost all of these devices have no viable ESD protection.

NBEMS, Radios and Digital Modes: Getting the Message.

Here's a screen shot from a recent Thursday night digital radio net that might help give you an idea of what it is all about if you haven't tried it.

The screen shot shows a received radiogram form as it would look on paper displayed on an Android tablet or phone.

Note: The only equipment used to receive this was an handheld radio (HT) and an Android Tablet. No cable, or interface, was used between the tablet and the HT.   The tablet's microphone decoded the audio coming out of the HT's speaker.

The app on the tablet is AndFlMsg which is a free Android application that implements a some parts of what's available in the FLdigi suites.

While in this case, the information for the form could have been relayed by voice, it could have easily been a picture, spreadsheet, or other file that would be difficult or impossible to relay by voice if the only available infrastructure was a radio.

Standard Container Manifesto

If you haven't seen it, see the  "Standard Container Manifesto" below.   It might help you understand some of the current buzz around container technology.   This one was added to the Docker README at one point but has been since removed.   There are better but longer descriptions.  

Note: to appreciate this, it helps to have been involved in the struggles of delivering enterprise IT where one of the core challenges, (if not the fundamental problem), is trying to get away from everything being somewhat different because it's all built by hand.

Oh, and if you aren't familiar with the story of the standard shipping container and its impact on global commerce, this looks like a reasonable overview:


Just like shipping containers, Standard Containers define a set of STANDARD OPERATIONS. Shipping containers can be lifted, stacked, locked, loaded, unloaded and labelled. Similarly, standard containers can be started, stopped, copied, snapshotted, downloaded, uploaded and tagged.


Just like shipping containers, Standard Containers are CONTENT-AGNOSTIC: all standard operations have the same effect regardless of the contents. A shipping container will be stacked in exactly the same way whether it contains Vietnamese powder coffee or spare Maserati parts. Similarly, Standard Containers are started or uploaded in the same way whether they contain a postgres database, a php application with its dependencies and application server, or Java build artifacts.


Both types of containers are INFRASTRUCTURE-AGNOSTIC: they can be transported to thousands of facilities around the world, and manipulated by a wide variety of equipment. A shipping container can be packed in a factory in Ukraine, transported by truck to the nearest routing center, stacked onto a train, loaded into a German boat by an Australian-built crane, stored in a warehouse at a US facility, etc. Similarly, a standard container can be bundled on my laptop, uploaded to S3, downloaded, run and snapshotted by a build server at Equinix in Virginia, uploaded to 10 staging servers in a home-made Openstack cluster, then sent to 30 production instances across 3 EC2 regions.


Because they offer the same standard operations regardless of content and infrastructure, Standard Containers, just like their physical counterpart, are extremely well-suited for automation. In fact, you could say automation is their secret weapon.
Many things that once required time-consuming and error-prone human effort can now be programmed. Before shipping containers, a bag of powder coffee was hauled, dragged, dropped, rolled and stacked by 10 different people in 10 different locations by the time it reached its destination. 1 out of 50 disappeared. 1 out of 20 was damaged. The process was slow, inefficient and cost a fortune - and was entirely different depending on the facility and the type of goods.
Similarly, before Standard Containers, by the time a software component ran in production, it had been individually built, configured, bundled, documented, patched, vendored, templated, tweaked and instrumented by 10 different people on 10 different computers. Builds failed, libraries conflicted, mirrors crashed, post-it notes were lost, logs were misplaced, cluster updates were half-broken. The process was slow, inefficient and cost a fortune - and was entirely different depending on the language and infrastructure provider.


There are 17 million shipping containers in existence, packed with every physical good imaginable. Every single one of them can be loaded on the same boats, by the same cranes, in the same facilities, and sent anywhere in the World with incredible efficiency. It is embarrassing to think that a 30 ton shipment of coffee can safely travel half-way across the World in less time than it takes a software team to deliver its code from one datacenter to another sitting 10 miles away.
With Standard Containers we can put an end to that embarrassment, by making INDUSTRIAL-GRADE DELIVERY of software a reality.

Saturday, January 17, 2015

Better PC Sound Card Oscilloscope software (windows).

TL;DR - Visual Analyzer, PC Sound Card Oscilloscope software.  Nice spectrum analyzer.  Worth checking out.

Through a really good YouTube Post on using an SDR for Frequency Deviation Measurement on FM transmitters I learned about Visual Analyzer. I should probably do a separate post just on this.

Previously I used Xoscope on Linux and Zeitnitz Soundcard Oscilloscope (

I had also found, but not used Zelscope, Soundcard Oscilloscope and Spectrum Analyzer.

I originally got some pointers on sound card osclloscopes, from Virginia Tech's Introductory Electronics courses that were based on their Lab in a Box, so that students would have all of their own materials for doing the electronics work without having to be in a physical lab.   See:

Virginia Tech, Experiment 12, Calibrating a Sound Card Oscilloscope

I only went so far with sound card oscilloscopes, because shortly after I started experimenting, the Rigol DS-1052E oscilloscope became available within my budget.  I bought it for $400 direct from China.  The Rigol caused a little bit of a revolution in terms of oscilloscope availability and pricing.

That was all back in 2009 and 2010 when I started reading a lot more about electronics.  In December, 2009, I finally took the exams from my amateur radio license.  I passed both Technician and General with 100% and went back for the Extra Class at the next exam session.  I got one wrong on my Extra.

Of course, the interesting bit that got me here writing this today is that the RTL-SDR stick can be used as the analog (ok radio frequency) front end for a software oscilloscope, spectrum analyzer, deviation meter, etc.  Especially for those of us without much in test equipment.

Monday, January 12, 2015

Intel Atom (Avoton) Mini-ITX (NAS) Server Build Notes

I'm building a mini-ITX NAS style server using Intel's low-power Atom server chip, known as Avoton.  The highlights are 8 cores, 64 GB max memory, yet passively cooled, quiet and low power, 20W TDP.The system's idle power usage without spinning disks is only 14 Watts. This makes it ideal for a SOHO file server, NAS server, lab box, etc.

The system I'm assembling resembles iXsystem's FreeNAS mini.  The main difference is that I went with the Supermicro motherboard instead of the ASRock motherboard.  I'll compare the two motherboards later and/or in a separate blog post.  However, I'll summarize my decision as The ASRock is better if you are going for a pure storage (NAS) box.  I went with the Supermicro as a better general purpose system with USB 3.0 ports and 4 x GbE ports.


Case and Power Supply

One of the most difficult decisions was trying to find a good case and power supply.  There is a lot of poorly designed cases.  There aren't many reviews for mini-ITX NAS-style cases. Through the reviews that are available I found one good choice which is also the same case that iXsystems uses for the FreeNAS Mini, the Ablecom CS-M50. Unfortunately the Ablecom isn't sold in the US directly.  It is primarily sold to OEMs in large quantities. I stumbled around for a while until a kind person clued me in that Supermicro sells the Ablecom CS-M50 as the Superchassis 721TQ-250B. It is even linked from the page for the A1SAi-2750F motherboard and I didn't notice it or assumed it would be yet another crap case.

The summary is the Ablecom CS-M50, aka Superchassis 721TQ-250B is a very nice case with real hot swap drive support. The most detailed reviews are actually for the FreeNAS Mini.  You can also find some reviews searching for the Ablecom CS-M50.

The one problem so far is that the front panel USB ports are USB 2.0.  The A1SAi motherboard has header connectors for USB 3.0, which use a different style header connector.   Currently, I've got no front panel USB ports. I've emailed Supermicro support.

Other People's Builds

Here are some of the sources that I used in making my decisions:

To Do

  • Determine what combination of hypervisors and operating system
    • Linux Host + VirtualBox
    • Linux Host + KVM
    • VMware ESXi
    • FreeNAS native FreeBSD
  • Solve Front Panel USB port connectivity problem:
    • Ideally there is a board from Ablecom, Supermicro or someone else that will give me USB 3.0 front panel ports.
    • Alternatively, an adapter cable that gives me USB 2.0 ports would be preferred.

Things I've Learned

  • The Supermicro 721TQ-250B case is the same as the Ablecom CS-M50 and is available at retail in the US.
  • The AST2400 IPMI BMC controller with fully integrated keyboard, video, and mouse, iKVM is very nice. I could have configured the system out of the box without ever attaching a monitor to.
  • The Supermicro/AST default Username and Password for IPMI is UPPER CASE and CASE SENSITIVE.  I mistakenly thought I couldn't access the BMC until I configured it through the BIOS.  The whole problem was the the default username and password were both all upper case.
  • As a result, the system is INSECURE out of the box. Change your IPMI/BMC username and password from the default as soon as possible. 
  • IPMIView from Supermicro/AST is pretty nice. It is a standalone Java Application. However the web browser interface is just as good or better for a single system.
  • The BIOS watchdog feature causes the system to be reset every 5 minutes.  Nothing is logged to the event log.  Don't set it, at least until you understand how to use it.   I think the Linux kernel is setting the hardware watchdog. 
  • An improperly seated SO-DIMM, caused the system to hang at BIOS POST, with the code B4.  However there were no beeps and I couldn't find a description of text error codes. The manual only gives the beep codes.
Hopefully this info will help others.