Monday, 26 December 2016

Santa Stopped Here

Unwilling to go to the trouble of watching out, not crying, not pouting and - worst of all - being nice rather than naughty, the kids round here resorted to posting stop signs, exhorting Santa to call at their gaffs yesterday.

Not wanting to be outdone by the little darlings, I joined in...

and - glad tidings of great joy - it worked!

I've never really had anything to complain about before, but Santa really excelled himself this year (aided and abetted by the XYL), providing the Rigol DS1054Z I've been sniffing around for a while...

Here are some proud boasts of a kid with a new toy first impressions, formed after opening the box and looking at some of the functions offered by this inexpensive instrument.

There's a great colour display and four input channels. There's the temptations of some software hacks to increase the available bandwidth above the cited 50MHz. There's also the promise of digital connectivity, which means an end to all those ugly oscilloscope screen photographs, which have blighted the pages of  'Shack Nasties' over the years.

Getting some screen images onto the computer was the first thing I tried - which involved downloading the two lumps of freeware which Rigol provide to accompany my new toy: UltraSigma and UltraScope.

With these pieces of code in place on the shack PC, I could hook up immediately to the new 'scope and see the screen. I achieved this first through the ethernet connection (just because I could) and then went back to the planned option of USB...

All of this was anticipated - I expected to be able to 'echo' the screen and its controls on the PC. What I didn't expect was that the PC display could provide different information to that presented on the (already more than adequate) seven inch screen of my new 'scope.

I can - for example - set up some measurements on the PC (making it do service as a multimeter and counter/timer)...

Here you can see that the sinewave I'm shoving into the 'scope to give you something to look at has frequency of 4.386 kHz and you can check its RMS value. You can do all sorts of other stuff as well - but we're only just getting started here!

Given the frequency content, it might be interesting to open an FFT window on the PC (you can do this on the 'scope too - but the bigger PC screen makes the additional graphical information easier to consume, whilst keeping up the conventional time-domain display on the instrument)...

Here (above) is the expected peak in the magnitude spectrum at the correct frequency. The FFT was being computed at something like 1 MHz sample rate, but I've changed the display to make things easier to see (which explains why the frequency resolution isn't so great). Here's the same signal, sampled at a lower rate (i.e. with the horizontal timebase slower), making the frequency resolution higher...

I've had this new toy for thirty six hours and I've been playing with it for a few minutes. It seems to me to be bursting with possibilities and it is absolutely amazing value for money. Plus, the XYL (who acted as Santa's little helper in this transaction) tells me that the UK agent was really helpful and good to do business with.

Here's one little boy who's been very lucky.

I hope you've been lucky too and I wish you all a very Happy Christmas,

...-.- de m0xpd

Friday, 23 December 2016

Forty-9er Shield

I've been tinkering with a quick lash-up of Wayne Burdick, n6kr's famous 'Forty-9er' receiver, implemented on an Arduino shield and tuned by one of my DDS systems.

Regular readers will remember how I tried running my Kanga / m0xpd Sudden-inspired receiver shield under the control of the new DDS on the Internet of Things board and found the latter to cause a lot of noise problems. I stripped out unnecessary active stages in the Rx shield to try to manage some of the receiver's susceptibility to the hostile EM environment generated by the ESP8266 and realised that I was left with something which resembled not only a Sudden but also any other SA602 / LM386 receiver - including the Forty-9er.

Interestingly, there's a guy in Asia who produces a CW transceiver with an ESP8266, available as a kit or as an assembled unit through our favourite auction site. This transceiver is rock-bound, and is offered with an app for an Android phone, which allows automated sending of CW. There's some implication that it was supposed to allow automated copying too but, from what I gather, that side of things isn't working too well. The transceiver is based on - you guessed it - the Forty-9er. (He also makes units based on Rock-mites etc.)

I figured that the combination of my beacon work (which does all the transmit side stuff) and my WiFi controlled VFO already adds up to way more than the simple CW transceiver mentioned above, which was what motivated me to investigate the IoT DDS / Receiver combo. But - as readers recall - I found it impractically noisy.

Well - if the commercial unit is offered and (one idealistically supposes) works with the Forty-9er, perhaps I should try the Forty-9er circuit too...

I found that I could take an empty prototype Sudden Rx shield PCB (with tracking for the DIL format 602, rather than the production version SMD) and bodge it for the Forty-9er circuit. The Sudden and the Forty-9er receivers are so similar that the PCBs can be re-worked to serve both roles with almost no effort.

Here's my new kludged Forty-9er receiver, atop the Sudden Tx prototype shield (which is only serving as a power supply, so most of the pins aren't connected) - the new ESP8266 / AD9834 board lurks behind the stack:

Here are details of what I've implemented on the shield:

Those familiar with the original Forty-9er will notice I've been forced (by the PCB) to deviate from the original recipe in a few ways:
  1. My input filtering network is implemented off-board
  2. I'm taking the output from the 612 OUT_B (pin 5), rather than OUT_A; simply an inversion
  3.  I'm applying the input to the 386 inverting input (pin 2) rather than the non-inverting input; another inversion
  4. I've added the 10uF capacitor between pins 1 and 8 of the 386; experiment showed I needed more gain to drive the speaker 
 All of these measures are not significant departures from the letter or spirit of the Forty-9er design (excepting 1 - which does have an impact which cannot be avoided in terms of layout).

The limited experiments to date show that the Forty-9er is better than the original Kanga / m0xpd HF shield (with its extra active stages) and possibly marginally better than the 'bare' Sudden. However, there is still a clearly audible clicking, which isn't yet - by any means - perfect. But, at least we're now at the point where I have a usable receiver.

I've not yet got a big enough inductor on the input to the 386 (the 'junk' box didn't stretch that far), so there is some performance gain to be expected in the original circuit when I get the correct magnitude inductance. Also, there is more to be done in experimentation with shielding / positioning, etc..

I've also searched the 'net for any mention of the clicking in discussion of the performance of the receivers - but to no avail. These devices have a very narrow (crystal) filter on their input and may derive some benefit from that strategy. If any reader has any direct experience of these units - or can point me to any evidence - please get in touch.

Now I'm off to continue with the tinkering, to listen to more clicking and - in between it all - to get lost in last minute preparations for Christmas,

...-.- de m0xpd

Sunday, 11 December 2016

Homebrew WiFi Shield

Having just finished development of the new m0xpd / Kanga ESP8266 - AD9834 board, I find myself with a few WiFi components knocking about on the bench - so I figured it would be fun to try to make a WiFi shield for an Arduino...

Using an ESP8266 (in a module, such as an ESP-12) as a WiFi shield for an Arduino is a little like using the proverbial 'steam hammer to crack a nut' - but these modules are frighteningly cheap and I do want a WiFi shield (which are surprisingly expensive).

I have a spare ESP-12 module on a nice breakout board with 0.1 inch pitch headers, just crying out to be used once again (it having done service in the early stages of the development of the connected beacon etc)

This could be a great opportunity to press the module back into some useful work and to teach myself something new.

I found a nice page about Sparkfun's ESP8266 WiFi shield and realised I could easily make a cut-down version with the module. Here's my schematic...

All that's needed is a power supply to ensure the current demands of the ESP8266 (on transmit) don't frighten the Arduino and a level converter for the software serial interface.

Regular readers will recognise my old favourite level converter, originally used in the Si570 board and later developed in quad and octuple parallel versions (although this time I'm using the familiar 2N7000 device, as I did in the level converter for the display driver in Occam's Dirk, rather than the fancy surface mount BSS138). To be perfectly honest, I'm not absolutely sure this level converter is required (I've seen some folks doing without it ) but it only takes a couple of shakes to build it and it only costs two FETs and four resistors, so it may as well go in!

Here's the completed circuit taking up almost no space on a prototyping shield:

 and here's the shield with the actual ESP module plugged in:

I fiddled around for a while with the code and eventually got the Arduino UNO (underneath the shield in the photo at the head of this post) to serve up a very simple web page, via the WiFi shield, on which it reported the analog levels read at each of its six analog input pins:

The response above is produced with A0:A4 floating (open circuit) and A5 grounded (hence the zero).

This success was obtained using 'brute force' AT commands (I started from the code prototype given here). My attempts to use WiFi AT libraries - including SparkFun's, - have not yet been completely successful. I don't yet know why - given that the shield is obviously working.

All-in-all, an interesting exercise and a nice way of getting a WiFi shield for 'nothing'.

...-.- de m0xpd

Saturday, 10 December 2016

ESP8266 Kit Released

The m0xpd / Kanga ESP8266 - AS9834 board, 'A DDS on The Internet of Things,' is now available for purchase as a kit, with the three SMD devices supplied already installed on the PCB...

The kit is provided (as usual) by the board's co-developer, Kanga Products UK.

Although this board is no more complicated than any other of my Arduino shields, it is rather different in scope and application. As such, I have set up a small website to support the board. The site provides details of the board's hardware and how to go about assembling and interfacing it.

More importantly, it provides some support to help new users get going with applications of this board. There are instructions for integrating the ESP8266 into the Arduino IDE and some test and application code for the new board - including a basic version of the multi-mode QRSS beacon.

I wish to thank Kanga for their continued support and encouragement in bringing my work to a wider audience. I hope that this board will be of interest to many experimenters who wish to explore the interface between ham radio and The Internet of Things.

...-.- de m0xpd

Sunday, 4 December 2016

Noisy ESP8266

Having enjoyed a lot of success transmitting and having produced a usable VFO, I decided it was time to try using the new m0xpd / Kanga ESP8266 - DDS board in a receiving application. I soon discovered just how noisy the ESP8266 is.

Above, you see the new board sitting on top of my old Leslie 825. The Leslie is next to the bench, which is too full of work and other projects to host a little game like this - so the impromptu receiver has spilled out onto the nearest flat surface.

Next to the IoT processor and DDS is an early prototype of the Kanga / m0xpd HF receiver shield (it differs from the production versions sold as kits only in that the SA602 is a lovely old original DIL version, as opposed to the SOIC surface mount versions supplied on the PCBs of the kits).

The receiver shield is actually on top of the transmitter shield used in recent beacon exploits (which includes a buffer for the local oscillator signal for the receiver - an inheritance from the 'Occam's Micro' days - you can ignore that for the purposes of this story).

To the left of the receiver shield is a filter system, originally developed for the "Occam's Dirk" rig (that recently had a Dutch makeover), which provides switchable input and output filtering for 40 and 20m.

I fired up this little combo, with the ESP8266 - DDS board running the recently reported WiFi controlled VFO system.

The result was a working receiver, with tuning from my iPad, marred by a horrible clicking sound. 'Marred' is an understatement. I should say 'made un-usable'.

Here is a segment of the receiver shield schematic, including one point where I'm going to report a voltage...

I powered up the system with the antenna input connected to a dummy load and recorded the voltages at the point 'MEASURED HERE' in the schematic above (conveniently available on a header at the edge of the receiver shield). Here it is, (with apologies for the nasty oscilloscope screen photo), explaining the horrible clicking sound:

There are short clicks every 100ms, of amplitude reaching at least -300mV. Remembering that there is another active stage (at 0 dB gain) and then the final LM386 stage (at 46 dB gain) after this, you'll understand that the output is driven to saturation on its power rails every tenth of a second, making the 10Hz clicking, which dominates the output. The miracle is that it is possible to hear activity on the band at all against all this bad behaviour!

First of all, the origin: Remember that the ESP8266 is being asked to establish an access point in order to run my WiFi controlled VFO program. Well, every 100ms, the system comes to the end of its 'beacon interval' in servicing that access point and makes some wireless activity (such as broadcasting its SSID). It is that which is causing the noise - but how is it getting into my receiver?

I found (somewhat to my surprise) that the greater part of the noise wasn't being received via the SA602 (this discovery was made by removing the chip - the reason I was using the early prototype version of the shield with a DIL mixer - and grounding the input to the Op-Amp). Instead, the greater part of the noise is actually generated by the twin Op-Amp package, where it was being directly detected / demodulated to AF. Some little of this 'detection' is also happening in the LM386 - but the op-amp seems to be the greater culprit.

The receiver actually seems closer to usable (notice I say 'closer to usable' rather than 'usable') without the op-amp in circuit at all - just taking the output straight from the SA602 to the LM386 (just like the original Sudden). Some part of the clicking which remains is directly demodulated in the audio frequency circuitry (the LM386). In the shield (unlike some implementations of Sudden-inspired DC receivers) this is operated with an unbalanced input. This experience of a very hostile EM environment caused by the ESP8266 might occasion a re-think of the receiver shield design. The remaining part of the clicking appears to enter through the intended (i.e. tuned) RF input...

Either switching the input filter to the other band or (equivalently) switching the VFO to the other band causes a big drop (>20 dB) in the clicking amplitude.

All the above is pretty disappointing; the ESP8266 and a simple receiver are uncomfortable bedfellows. There needs to be some careful layout and some circuit re-design before a WiFi module and a simple DC receiver can sit next to each other easily. This isn't exactly news (noise problems have been reported before in trying to close-couple an ESP8266 and a 2m transceiver) but it sure puts the brakes on some plans I had for the next few weeks.

Finally, for something really wierd...

I re-programmed the ESP8266 with some code which just set the DDS frequency. No access point, no WiFi activity. Nothing. Just a quick set-up of the DDS on 40m and then just sit there in an endless loop, twiddling its thumbs.

The result?

You guessed it - exactly the same 10Hz noise!

The chip is still pumping out noise pollution, even when the code hasn't asked it to do anything fancy. I don't know if this is a failing of the IDE (I was using the Arduino IDE, and I don't know if the compiler doesn't turn off the WiFi resources if they've previously been turned on in an earlier program). I don't even know if it is POSSIBLE to turn off the WiFi resources (though I believe it is). All I know is that a piece of code written to evoke NO WiFi functionality at all is producing the massive noise fields around the device as are present due (presumably) to WiFi activity. Wierd.

So - I have a working, WiFi tuned HF receiver running. It is just ruined at present by some nasty 10Hz clicking, which makes it just about worthless. I don't know if it can be fixed.

It has certainly put a dent in my enthusiasm for the ESP8266.

...-.- de m0xpd

Sunday, 27 November 2016

A WiFi-Controlled VFO

Now that I have placed a DDS on a board with Wireless connectivity, it is only obvious to set it up as an AP Web Server and allow remote control via a 'soft' user interface...

When I first started to play with the AD9850 DDS, I made some beacons and wrote the Kanga VFO demonstrator code (as application code to support the Kanga / m0xpd DDS shield). Well, now I've produced this new internet savvy AD9834 DDS board, I've followed the same pattern; I've done the beacon thing and now - in this post - I'm covering the VFO. Only, of course, this VFO won't have physical knobs and buttons like its predecessor. Understand, it could have all the physical controls if you wanted it to - but that's not the point. Instead...

When  the new code fires up, the ESP8266 sets itself up as an access point and offers a new wireless network:

which you can join from any phone, tablet, computer or similar wireless enabled device. This will provide the interface to the VFO. The network name 'm0xpd Kanga DDS 94TD' is formed of a generic part ('m0xpd Kanga DDS') and a four character index associated with the particular board (such that two VFOs in the same area could operate independently).

Opening a browser and going to the VFO's 'web page' will open the simple control interface seen below, which reports the frequency at which the oscillator is running, offers 'buttons' to adjust the frequency and 'buttons' to change band:

The picture above is a photo of my iPad mini screen, controlling the VFO. I've added the red annotations to make it clearer for you.

The web page is generated entirely by the m0xpd / Kanga ESP8266 - AD9834 board - the iPad is just interpreting it (as HTML).

Clicking on any of the 'Adjust Freq' hyperlinks will cause the VFO frequency to change according to the label. Clicking on any of the 'Select Band' hyperlinks has the obvious effect.

All this is rather dynamic and needs a video to demonstrate (which I haven't provided) - so here are some rather dull 'stills' of the system on 40 metres

and 80 metres...

And here's a 'sniff' of the requests received from the web page of sequential increments and decrements in frequency whilst on 80m, along with the resulting frequencies...

This code will be released as an application 'demo' for the new m0xpd / Kanga ESP8266 - AD9834 board (along with a multi-mode beacon).

Of course, the demo code above is intended only as an illustration of what is possible. The rather dry web page could be replaced by an application, written specifically to control a different piece of VFO code, etc.. This is just a start point - but it sure gets me thinking...

There are other exciting opportunities to be exploited via this access point - watch this space!

...-.- de m0xpd

Friday, 25 November 2016

Occam Going Dutch

Kees, pa5cw, has produced a new variant of my 'Occam's Dirk' software for a multi-band CW transceiver.

'Occam's Dirk' was a multi-band development of the original 'Occam's Microcontroller' concept, adding automated 'CQ' calls and one or two other little refinements (like RiT, VFO A/B, etc). The original 'Dirk' was presented with an Si5351 in the RF generating role (as I wanted to try using the then new Kanga / m0xpd Si5351 shield).

Kees has decided to revert to the AD9850 DDS for his version of the code, which makes the architecture similar to that introduced in my 'Kanga VFO' demo software (and elsewhere).

Kees has also added some new functionality: the means to change keyer speed using a voltage input to A0, most conveniently generated by a potentiometer. The original code had speed change as a software function under the menu system - which works, but isn't immediately accessible for a quick change.

I've always built keyers into my software (and provided both a paddle and a straight key input) but - if I'm honest - I've seldom used these keyers in anger. Here at the shack, I usually drive all my rigs (via their straight key input) from the old faithful "Funky Keyer", which has its own physical speed control. Thus, menu-based speed adjustment of the software was never a big handicap for me. But Kees' approach certainly is convenient (at the expense of one knob).

Any of you interested in trying Kees' code can find it here on the Occam's Software page. I haven't tried running it - but I have confirmed that it compiles correctly.

Many thanks to Kees for sharing his work,
...-.- de m0xpd

Saturday, 19 November 2016

SNA Junior

I have (finally) got round to building my own instance of DuWayne, KV4QB's prize-winning Scalar Network Analyser Jr:

and a great little instrument it is too!

DuWayne and I have been corresponding for a couple of years, sharing mutual interests. I was pleased to be able to give his work a shout in both the printed and  'spoken' version of my talk at this year's Four Days in May event in Dayton and - more importantly - to catch up with the man in person for a quick eyeball QSO. I also got a PCB for SNA Jr, which has been sitting on the bench for months - until last week.

The SNA board finally bubbled up to the top of the pile and I looked around for the bits I needed to complete it. Perhaps I should explain (to those of you who don't know) what's involved...

DuWayne's baby uses an AD9850 in one of our familiar modules to generate RF, under the control of an Arduino NANO. You can read on DuWayne's blog how the SNA Jr is the descendant of earlier experiments in which an Si5351 was used as the signal source.

In the SNA Jr, the output from the DDS is fed to the device under test and the returned signal is observed in a detector system. DuWayne has 'history' in using simple diode detectors in this role (and I was praising kv4qb for this minimalist approach in my talk at Dayton) - again, you can read about this lineage. However, the SNA Jr now replaces the earlier simple diode detector with a fancy AD8307 detector, in the well-known Wes Hayward, w7zoi, circuit. This gives superior performance in terms of dynamic range and 'linearity'. Also, with the availability of cheap AD8307s (of dubious parentage) from China, this option is also becoming attractive for cheapskates like me! [I have some Chinese AD8307s on order and will report back on performance when the slow boat docks.]

You can't see the detector in the photo above, because it lurks under the screen - so here's another shot (with apologies for my wayward handling of some of the SMT devices):

The detector is supposed to be enclosed in a screening can, which I haven't made yet - so final performance will be better than I'm going to show you below.

The DDS RF source and measurement of the RF level returned from the device under test are all under the control of the little Arduino NANO, which runs a sketch provided by DuWayne. This sketch compiled for me under Arduino 1.6.12. The user interface is provided through just a rotary encoder and the 1.8 inch TFT screen.

I found I had everything needed to build SNA Jr in the 'junk box' - except the screen and a spare NANO, so these were quickly ordered through usual suppliers.

The result, as you see above, was simple to put together and works very well.

DuWayne's software offers a number of options, including a 'signal generator' mode, in which the output of the DDS module is set at a single frequency, whilst the returned RF amplitude is displayed numerically and on a bar display (useful when the numerical display is flicking between two values). This mode is illustrated in the graphic below, which shows the system driving a simple switched attenuator, seen in the graphic, with and without 20dB of attenuation switched in (two 10 dB stages).

I'm sure the (in)accuracy of the -20dB step is down to my cheapskate attenuator (with its low tolerance resistors, lack of screening etc.), rather than SNA Jr.

Another, more important series of modes sets the DDS module generating RF sweeps, which result in graphical displays. These are illustrated below, in which I've contrived a test of the low pass filter which has been conditioning the output of the 'connected beacon' (Blogs passim) on 30m.

SNA Jr can also be used with various 'attachments' such as a 40dB tap (with which DuWayne's software allows it to function as an RF Power Meter) or a Return Loss Bridge, with which it can perform SWR Scans.

Here's a scan looking into my (g5rv) antenna, with (right) and without (left) the Made-from-Junk 'Deluxe' Versa Tuner II switching in tuning appropriate for operation at the CW end of 40m...

As you see from my additional labeling in the graphic above, the scan was set up to run from 6 to 8 MHz. I reported an equivalent measurement on my own system (originally reported here) in one of my slides at FDIM (although it was presented in terms of Reflection Coefficient, rather than SWR)...

There's even more to SNA Jr - it can even locate minima to impersonate a dip meter (but I haven't been able to try this yet).

I said at the beginning of this post that SNA Jr is 'prize winning'. DuWayne won the 'Best in Show' award at  the homebrew competition at FDIM (which is no mean feat, given the very high standard of the submissions I saw there, in several widely different categories). The prize was well-deserved.

The project was written up in QRP Quarterly (vol 57(3)  pp 22:25, July 2016) :

which is nice to read. But the best thing to do is to get the information from DuWayne's blog and build an SNA Jr for yourself  - or take the inspiration to build something similar.

Great fun - thanks, DuWayne.

...-.- de m0xpd

Saturday, 12 November 2016

ESP8266 Production PCB

The first sample of the production version of the PCB for the ESP8266 / DDS system arrived a couple of weeks ago.

As you see, it follows the plans established in the earlier prototypes, with the surface mount components already fitted (such that tyros don't need to face the challenge of dealing with these pesky little things).

I've been detained by work and by a short break up in M-land, where I stayed on the banks of the River Nith, playing at being mm0xpd/p. However, now I'm home, I've stuffed the new board - this time with the intended 1/8th Watt resistors:

I set her up for a quick test yesterday morning, programming the ESP8266 with my beacon code and plugging a Kanga / m0xpd TX shield on top of the new PCB. Here are the WSPR spots accumulated on 30m in the first thirty minutes (from 09:00 GMT):

Looks like things are working FB.

I had a nice time working CW, PSK-31 and even a little SSB on my TS-480 yesterday, so the station was out of commission for beacon operation for most of the day. But I turned the beacon back on in the evening and let it run overnight.

Here are the accumulated 24 hours of spots on 30m ...

(It looks even better as I write, 'cos I'm also down to Stewart, w4mo in Venice, FL - but you've got to draw the line somewhere).

I hope it won't be long before Kanga can offer the new board as a kit to anybody interested in playing similar games.

...-.- de m0xpd

Sunday, 4 September 2016

New ESP8266 Board

Kanga UK and I have been developing a new board and I can bring you some pictures of the first engineering sample...

You can well see it is an engineering sample, because I'm squeezing the wrong size packages into locations (quarter Watt resistors where eighth Watt components should be, etc) and using a mishmash of different component types, but you'll forgive me, I'm sure.

The new design presents the Expressif ESP8266 device on an Arduino-sized board, supported by a full USB programming interface and power supply.

I should be careful to explain - this is not a "shield". It does not sit on top of an Arduino. It REPLACES the Arduino. It IS the processor - and a whole bunch more...

Of course, there's all the interfacing headers you'll need to connect it to other expansion devices ("shields") from the Arduino ecosystem. This is nothing new - it is already available in commercial platforms out there, such as the WeMos D1 R2 (indeed, I made this new board largely compatible with WeMos' digital I/O pin allocations).

Of more relevance to fellow amateurs, this new board includes a DDS system, capable of generating stable, controllable RF, using the AD9834 device.

You have here a powerful processor - significantly more capable than that on (e.g.) the basic Arduino UNO - with a full, on-board DDS system. All with access to the advantages of the Internet (time servers, geolocation, remote control, ...). All on one little board.

The overall architecture is seen in the image below...

The output from the DDS module is taken to the header on the upper left hand edge of the board in the orientation of the photo above - which is the m0xpd RF bus I've defined previously for other shields. This facilitates the first application for the new board: to implement a beacon system, using the Kanga/m0xpd Sudden Transmitter shield, which can simply plug on top of the new board to make a complete beacon assembly.

The USB interface is implemented using a genuine FTDI chip, with the hope that interface problems should be minimised. However, I've just had all sorts of problems after upgrading the operating system of my MacBook Air to El Capitan, after which it seems incapable of operating reliably with ANY external peripheral - not just the FTDI devices.

The new board has flexible power supply options. It can be powered off the USB connection. It can derive power from the 5V supply from the Sudden Tx shield in the beacon application described above or it can be powered through the d.c. power jack visible at bottom left of the photo.

Of course - the collaboration with Kanga signals that this board - or the final production version - may soon be available for purchase as a kit. With the experience of the m0xpd Si5351 shield, we have discovered that many Kanga customers are not great fans of surface mount technology. Accordingly, this system has been designed with the intention that key SMD elements could be delivered pre-fitted...

leaving the kit buyer to fit only thru-hole components, one large voltage regulator and the ESP8266 module itself.

Here, finally, is the engineering sample, plugged into a Sudden Tx shield (itself a prototype) for the very first time to run my beacon code as a "stack"...

The little OLED display on the breadboard at bottom right is there just as a sign of life.

Although not so good these last two or three days, when it has been harder to burst far out of Europe, the same technology has been running WSPR and QRSS all over the globe for the past couple of weeks, as recent posts testify.

I hope that this new board might tempt some more radio hams to look toward the ESP8266 and the"Internet of Things" for inspiration and fun.

...-.- de m0xpd

Wednesday, 24 August 2016

USB Mini Breakouts

If, like me, you ever fool around with USB hardware and choose to do so in the context of solderless breadboards, you might well need a little breakout board for one of the several types of socket - in my present case the USB mini-B receptacle.

There are, of course, lots of lovely commercial ways to scratch this itch, available - for example - on our favourite auction site...

but I wanted one now, rather than in a day or two's time (or longer, if it had to take the slow boat).

Of course, I'd been getting by with the usual solution of a butchered cable with a type A plug at one end and some pins on the end of bare tails I'd made at the other...

but I wanted to get rid of this 'trailing wire' and fit a neat socket.

I had some surface mount mini-B receptacles in the junk box and noticed that the connector pitch was close enough to the 0.95mm spaced pads on one side of a 10-pad SOT23 DIL carrier...

So, with a little judicious bending of the outer pair of pins, a 5-way strip of male header pins and some solder, I soon had my own USB mini breakout...

Here it is in action on the beacon...

I don't think I'll even bother to order any from the Far East - they're too easy to make!

...-.- de m0xpd


Friday, 19 August 2016

ESP8266 Geolocation

The ESP8266 device, used as the heart and soul of my new beacon, knows its place in the world...

This post describes a couple of techniques for 'Geolocation' on the ESP8266 and uses them to derive the location information my beacon needs to broadcast (e.g.) a valid WSPR message.

Readers may remember I grafted a GPS module onto an earlier beacon system here in the shack - mainly for time synchronization - but don't know how much trouble I had with it (a north facing window made GPS reception VERY difficult).

Having my new beacon sat on the 'Internet of Things' opens up a new possibility for obtaining not just time (which I've already reported) but also position information, using geolocation. So - I decided this was a worthy avenue for experiment, both for the practical end of getting the location by other means than GPS and as an interesting learning exercise.

It turns out that Geolocation, by the methods I'll describe below, is a standard alternative to positioning via GPS in those places where a satellite signal cannot be obtained (indoors, underground etc.).

I'll describe two broad methods - and present working ESP8266 code to illustrate each.

The first uses your own IP address to provide a rough estimate of location, using a service such as Freegeoip. Adafruit has posted a very good example of how to use this service here and I've modified their code to provide a stand-alone application for the ESP8266.

The code on the github link above is presented as a sketch for the Arduino IDE. You'll need to modify it to include your own WiFi network's ssid and password before it will work. It will print the results into a Serial Monitor window (at 115200 baud).

I included an elaborated version of this code in my beacon, to generate the following location estimates on the little screen...

Clearly, it knows I'm in Manchester (!), but the map reference turns out to be quite a bit off...

It places me at a location about 8 km away from my actual QTH, as seen in the map above (the erroneous location is seen - not my home - this isn't an invitation for thieves).

All this might not matter too much, but for the fact that it is actually in the wrong (six-character) Maidenhead locator square...

This shows an incorrect placement in IO83uk when actually I'm in IO83tk.

Not too serious - but a reflection of the poor absolute accuracy of the location estimation afforded using this first IP-based Geolocation method. Remember - it is 8km out. In fact, as I write, is returning a location estimate which is much poorer than that - bang in the middle of London!

An alternative method clearly is needed to accurately resolve the correct locator square.

The second method, known as the WiFi positioning system or WPS, uses a scan of all the WiFi Access Points visible to the ESP8266. The result of this scan is uploaded to a Geolocation API, such as those offered by Google or Mozilla.

Both these services are entirely free to use, but Google make you jump through a lot of hoops to get an API Key. Mozilla is hoop-free.

I've written some code which shows how to access these services using the ESP8266 here.

The important part of the sketch is shown in this extract...

After setting up the important credentials for accessing the API (Host, Page and access key), the HTTPS client needs to be instantiated (it needs to be the Secure version of the WiFi client - so this won't be easy or even possible to run on a lesser processor than the ESP8266).

After this, the POST is fairly conventional (see, for example, the example at the bottom of this page) but it did take me a long time to figure out exactly how to get it working!

Here's the beginning of the result of the WiFi scan, as produced at my QTH, showing some of the WAPs visible here...

It is in the JSON format produced by the code and required for submission to the Geolocation APIs.

WPS databases operate in context of the mobile telephone industry and require that the header includes some parameters which spoof the API into believing that the request is coming from a mobile device with GSM capability. I used a Mobile Country Code and Network Code associated with a local network provider in the UK (which I looked up in a table). If you're not in the UK, you should probably choose a different MCC and MNC.

I also used the ArduinoJson library to handle the result from the Geolocation API.

With this method, location results have an accuracy of order metres, so an elaborated version of the code was implemented in my little proto-beacon...

Now we're in the building (actually, we're in a house at the bottom of my garden, but that sort of error I can live with).

With location and time (from the NTP servers, as previously reported) I have all the ingredients required to automatically generate a WSPR message, instead of going through the chore of generating it ahead of time in a command-line utility on the PC and uploading it as a constant into the beacon...

I looked at Gene, w3pm's on-line materials, among which are several Arduino sketches including a function 'void wsprGenCode()' which generates WSPR messages. This works perfectly well, but calls several other functions and isn't the easiest item to work with.

Fortunately, a further quick search produced John Newcombe's elegant WsprMessage c++ class, which I am now using. It is producing my WSPR message very efficiently...

Credit where it is due: both Gene's function(s) and John's class (/library) draw heavily on the work of Andy Talbot, g4jnt, who has produced a detailed explanation of the WSPR coding process.

The entire beacon now is literally turn-on and go, in any location with a WiFi connection. It ran last night on 30m with an unusually strong performance into S America...

although this seemed to be at the expense of contacts into the antipodes.

I hope others are as excited by this collision between amateur radio and the Internet of Things as I am - it seems alive with possibilities.

...-.- de m0xpd