Slice of Pi - a simpler construction method

[DavidC]

I was intrigued by ianfallon's pictures and build of a Pilotaware box using the Slice of Pi adaptor instead of Digole board (or POD module).
Since I'm still awaiting the Digole board in the post from China, I went ahead and got one which I built last night. All good to go.
I thought this was much neater than the other two methods, since it simply plugs into the Pi (although you still need to solder four wires).

Some pictures below show the construction method I used. I stuck the ARF board to the Slice of Pi with four little sticky pads (used for card making) and put some insulating tape over the metal HMDI socket. The whole assembly fits neatly into the standard red Pi box sold with the Pi itself from RS.

Now I just have to find someone else who's got one to see if it really works, although the diagnostic screen messages look promising.

[trapdoor]

Think I was probably the first one to use this board after ordering one in for my first build & posted in the 'enhancement requests' thread, but I'll not hold that against Ian who posted his pictures after he built his up.   

I'd suggest for mechanical robustness, you use the plastic nut and bolt that comes with the SoP board - it's used as a support 'leg' but because it bears on the HDMI connector on the RPi board needs to be carefully cut down so it sits exactly on the metal can of the connector when the SoP board is plugged on. Even though the ARF board (and the barometric sensor board when embodied) aren't heavy, vibration in an aircraft could make it unreliable. See the pic below for where the bolt is on my build- although mine has moved on from what is shown there as the ADS-B antenna is now co-located with the ARF antenna on the end of the unit.

[ianfallon]

Yes - all credit for first SOP build goes to trapdoor 

[Richard]

although mine has moved on from what is shown there as the ADS-B antenna is now co-located with the ARF antenna on the end of the unit.

trapdoor,
    There as been chat about the ADS-B Antenna been the wrong frequency for the reception.  I can now confirm it is and will not work to receive the ADS-B traffic ( If you have managed to receive traffic with your setup, I would be interested to see how you have achieved this. I have the same areal configuration you have in the photo.  Once plugged back into the original supplied ADS-B antenna, all works fine again. Your configuration looks neat so I followed the same line as you. But no luck receiving with the short antenna.... sorry

Richasrd

[ianfallon]

It might not be the most precision instrument but I've seen traffic S of the Isle of Wight from Banbury with my unit on the ground so it's plenty good enough. Using a cheap £8-10 dongle and aerial. I've you're getting nothing then there's another problem.

[Richard]

Ian,
   Sorry.... My post above is misleading.... I was referring to the use of the the small rubber antenna used instead if the originally supplied larger wire areal that comes with the DTV Dongle.   Yes My PilotAware will receive traffic almost from Coast To Coast  (We are on top of a hill in the center of yorkshire) I'm trying to tidy the pilotAware box without have wires poking out every where...

[trapdoor]

With my small antenna (which is effectively a GSM900/1800 antenna) I can get traffic out to the South East coast of S. Ireland!!

See below.

Whilst it's not tuned to the 'ideal' frequency, It is actually better than the supplied antenna in its uncut (untuned) form which is a DVB-T antenna tuned probably to around 700Mhz - verified on my DSO running FFT (effectively a spectrum analyser)

My latest incarnation has the ADS-B antenna at the same end as the ARF antenna - again see the pics...

You really need to make sure that you aren't shorting the input with whatever antenna and adapter you are using as that will kill any chance or getting anything at all. The antenna I use is this one:

http://www.ebay.co.uk/itm/361362426353

I now have two boxes working perfectly with the small antennae, a third in build (waiting on the DVB-T module from China). The plan is (was) to move the DVB-T module inside the case but I'm reasonably happy with things at the moment and I don't particularly want to butcher the RPi to hard-wire the USB. But it's a plan for the future and I think there is just enough room inside the box.

[Richard]

Trapdoor,
    Thank you for your reply.  I have been trying to used one of the small antenners from here

https://www.wirelessthings.net/868-915-mhz-small-rubber-duck-antenna  for the DVB-T

I see the frequses are slightly different to the one you have sugested. I will order the same as you to try to reproduce your very neat solution.

[N6010Y]

Hi Folks,

Just joined the forum and ordered most of the hardware to start my build. A few questions if I may?  Bearing in mind I'm a mechanical engineer and not an electronics guru - clanky answers work better for me!

1.  My set-up will be:  iPad mini with both cellular and GPS outputting the GPS data to PilotAware, and connecting back to SkyDemon via the FLARM option;
2.  I like the idea of using the SOP instead of the other board - looks a nice solution - What mods need to be done to the SOP board prior to using it instead of the Dogole board?
3.  When using the SOP - how does the 3.3 v get supplied to the ARF board?
4.  Is there a step by step guide with pictures (similar to the construction/build pdf file) that shows each step in order to build the unit?
5.  The Wirelessthings ARF receiver seems to be be out of stock - anywhere else I can source one - I've checked eBay and Amazon - no go!
6.  Is it ok to ask more questions as the build progresses !!!!!!
7.  Any other practical advice greatly appreciated!

Many thanks

[trapdoor]

1.  My set-up will be:  iPad mini with both cellular and GPS outputting the GPS data to PilotAware, and connecting back to SkyDemon via the FLARM option;

That's how most of us do it -- but there is now an option to use a USB GPS directly into the PilotAware unit (testing myself at the moment)

2.  I like the idea of using the SOP instead of the other board - looks a nice solution - What mods need to be done to the SOP board prior to using it instead of the Dogole board?

The POD headers that are in a line need to be removed. Unsolder if you feel confident enough and have a decent de-solder pump, otherwise wiggle from side to side a few times and the pins will break off flush(ish) with the PCB. You can then either just leave them and cover with tape or de-solder each pin (what I do).

3.  When using the SOP - how does the 3.3 v get supplied to the ARF board?

There is an on-board regulator. It feeds a set of pads that have a screen printed legend of GND and 3.3V - there is also a 5V pad next to it so be careful which ones you use.

4.  Is there a step by step guide with pictures (similar to the construction/build pdf file) that shows each step in order to build the unit?

Nope. But it's fairly self-explanatory. You just need 4 wires. There are photo's that both Ian Fallon and I have posted. I have attached one below showing my initial SoP board with ARF.

5.  The Wirelessthings ARF receiver seems to be be out of stock - anywhere else I can source one - I've checked eBay and Amazon - no go!

I bought one from Rapid Electronics but they are also out of stock. WirelessThings say they will be getting more 'soon'. Sign up on their website to get an email when they are in.

6.  Is it ok to ask more questions as the build progresses !!!!!!

Yes. We will help if we can.

7.  Any other practical advice greatly appreciated!

Look at what others have done and decide what's best for you. Everyones approach is different but as long as you build to the plan it should work OK. The most important thing is to buy the modules that Lee has stated work. Don't think 'that looks the same, i'll get one of them instead' as it may not work (as per some of the WiFi threads).

Good luck and have fun.

[AlanB]

I used the Pi SOP (not the wireless things) and made the following mods.

The 3.3v pad on the SOP is connected direct to the GPIO socket so broke that link and then fitted a 5v to 3.3v regulator between the 5v pad connected to the GPIO 5v line and the 3.3 input pin of the ARF as the ARF needs more than the 3.3v limited current than the GPIO can supply.

The TX pin is connected direct to the GPIO board and again based on research I broke the link between and put a15K resistor to ground and a 10K resistor in line to protect the ARF input from the 5v  signal as according to the specs on the wireless things website its sensitive to volts.

It might be that the humble pi board, which is slightly bigger but should fit in the case is the better option as I think the connections are already open - others may have more information on that.

I used the XRF document here: http://openmicros.org/index.php/articles/247-xrf-document-index as reference.

not been able to verify if all of this works yet as only just got the ADS-B element working and no way of checking of what I have done works for the ARF.

Sorry for the clumsy description maybe someone has drawn something up in pictures that would help.

[trapdoor]

The 3.3v pad on the SOP is connected direct to the GPIO socket so broke that link and then fitted a 5v to 3.3v regulator between the 5v pad connected to the GPIO 5v line and the 3.3 input pin of the ARF as the ARF needs more than the 3.3v limited current than the GPIO can supply.

That is NOT correct. The WirelessThings Slice of Pod board has a 5v to 3.3v regulator on board. There is absolutely no need to add another regulator and the 3.3v is not obtained from the 3.3v RPi header.

If you look at the photos on this thread, you can see the regulator on the board.

Also the UART on the RPi is 3.3v NOT 5v

https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=9931

So there is no need to clamp the I/O of the ARF

[AlanB]

Sorry Trapdoor I didn't use the Wireless Things SOP I used the PI SOP.

Sorry for confusion 

[N6010Y]

WOW - I got a bit confused there about having to insert a voltage converter, but I'm glad it's been cleared up.

I guess I need to buy the correct SOP board - I didn't realise there were different types - jikes!

[trapdoor]

Makes sense to use the WirelessThings Slice of Pod board because it saves having to pfaff about with a Digole or Power Pod as it has a nice, beefy regulator, gives some mechanical rigidity to the build and allows the easy mounting and wiring of the soon-to-be 'necessary' (but not mandatory as far as I know) Barostatic module.

It's cheaper than the Digole and just order one at the same time as the ARF that you need to order anyway. The mod of the board to fit in the smaller cases is 30 seconds of 'wiggling' the pod headers until they snap off. Or spend 15 minutes unsoldering properly if you are OCD like me