This thread picks up from here and the discussion of a “DIY solution”
Years ago I investigated ways of displaying data from “portable devices” on my KMD550 MFD.
There are basically two ways of achieving this. One is to use an NTSC video input, which some MFDs used to display radar images. The KMD550 does this, as the above writeup shows. The quality is poor but good enough. The other way is to fake TCAS data; this needs access to the protocol which is not published (you need to sign an NDA and it has resisted all my dodgy attempts to get it via contacts in low places) and it involves defining a custom symbol set (A-Z, 0-9, or little pixels) and then placing these at x,y locations to draw whatever is needed. This is standard “fun software” stuff; a few days of a competent programmer’s time. A slight catch is that the TCAS data needs to be in ARINC429, in this case, but some Avidyne MFDs accept TCAS via RS232. No idea about Garmin – nobody replied, here or anywhere, though I believe no current Garmin product does video, other than some oldies they bought; MX20?
“Obviously” (?) it is illegal, but it would be safe and extremely useful.
The Q is whether the ADL box[es] has/have any serial data output. The mfg could implement such an output legally; it is not for them to worry what somebody does with it.
Then you could end up with the functionality of a MLX770 (10-15k installed?) but at a fraction of the price.
What’s the details of the satellite services used? I’m just thinking that those of us on even tighter budgets might be able to do something with the Raspberry Pi 3…
I’m not thinking about a commercial product, I’m thinking of a roll-your-own satellite weather system. There’s a lot of fun things you can do with software defined radio if you can do stuff receive only (i.e. not have to worry too much about approval) if the weather data is a broadcast, rather than doing this as satellite internet etc.
I did this route here with the Thuraya 7100 phone, with a colleague under linux. 9600bits/sec, $1/minute, RS232, cheap, but strictly for computer anoraks 
Even the Thuraya XT phone I now use, 50000bits/sec and $6/MB flat rate, is just for anoraks and could never be sold in the context of a commercial product.
Any commercial product (like the ADL) has to use Iridium otherwise your tech support dept will implode. Thuraya works very well but has quirks and people in the infidel West demand very close to 100% and Thuraya does not deliver that. I believe their system was originally designed for millions of nomadic users in the Middle East (where Thuraya are run from) and other poor areas, and indeed their 20p/minute call rate (T to T) supports that. Nor can one communicate with them at anything remotely resembling a technical level.
You can get cheap old Iridium RS232-interfaced satphones on Ebay but the data rate is only 2400bits/sec which is useless unless you run your own server which prepackages the data. Iridium cannot be used (realistically) for the open internet. Even DHCP takes some tens of seconds, IME. Data on Iridium needs to be run between a dedicated server (possibly running raw UDP for stuff like wx images, where losing a few lines is OK) and a dedicated client app.
Details posted here previously on various occassions. Check your spam box @Alioth although possibly no longer relevant.
I did post here previously about a proposal to radiate wx data (unidirectionally) below the noise floor and recover the signal using old signal processing methods but tomjnx said this is impossible
Iridium/Thuraya also implies it has to be two-way and not a broadcast (and as such, roll-your-own with a software defined radio is out of the question). Probably for UK VFR flying, tuning into VOLMET will still be the order of the day!
Peter wrote:
I did this route here with the Thuraya 7100 phone, with a colleague under linux. 9600bits/sec, $1/minute, RS232, cheap, but strictly for computer anoraks Even the Thuraya XT phone I now use, 50000bits/sec and $6/MB flat rate, is just for anoraks and could never be sold in the context of a commercial product.
I just read that article of yours, very interesting. An approach I would consider is putting the Thuraya phone and a Raspberry Pi 3 (has built-in WiFi) together in a box and using it as a “satellite MiFi” (that’s presuming the Thuraya phone doesn’t have a weird proprietary software interface for its USB connection, or if it does, someone’s made libusb drivers for it). The Pi has enough grunt that it could not only run a firewall but a local proxy server which would give a great deal of control over what goes on with the internet connection, and will allow it to be shared with any tablet computer (e.g. an iPad running Skydemon, and allow all the features of Skydemon to be used while flying – Skydemon now has cloud/radar overlays which presumably only fetches the data it needs since the base map is already on your device).
Plus of course all the other features of the phone its connected to (ability to send text messages, or use iMessage if your tablet is an Apple device, etc. etc.)
Sure it would still be a “computer anorak” thing but I think there’s quite a few of those amongst the LAA membership, and they aren’t afraid to get their hands dirty :-)
The 7100 is RS232 and emulates a Hayes modem. The AT commands are published e.g. here [ local copy ]
The only challenge is making it hang up reliably. One has to do the ~~+++~~ATH0 stuff and drop DTR; that usually works. But really the pilot needs to have visibility of the phone’s screen, to make sure, at $1/minute 
The XT phone is USB only. There may be a serial interface but it is not documented. USB drivers exist for winXP through to win8 and that’s it, AFAIK.
The other Thuraya phones (between the 710x and the XT) are crap.
The other challenge, often discussed here, is that the sat phone connection gets swamped by all the crap which modern devices send back to their Church of Apple / Church of Google / Church of Microsoft. This is very frustrating because it hits you right when you least expect it – on a flight when you need the connection but some bloody app decides to send a 5MB report to Google Cache or whatever. The ADL approach of running only to your own server (and firewalling everything else) solves that but you don’t get open internet access even if the connection was fast enough (which on Iridium it isn’t). I now have everything firewalled except 2 private wx sites and Telegram’s hopefully fixed IP.
BTW Telegram needs the XT’s speed; it won’t work usefully on the 7100.
Thuraya also do / used to do modules, which is the logical way to build any satcomms product.
There are various gotchas with Thuyaya; from memory -
This would be a nice thing with mating a satphone with a Raspberry Pi 3 – you can build a wireless access point with a very good and smart proxy server built in (run something like Squid proxy) and no one’s doing anything you don’t specifically authorize. The nice thing about a proper proxy server versus just a plain old packet inspecting firewall is that you can get much more fine grained, right down to blocking just parts of a website you don’t want to download, blocking all files of certain filetypes etc, and of course running on the access point this applies to all devices that connect to it. It could also be set up to use a parent proxy running on a server somewhere else, for instance if you need to get to a site that’s being blocked to IP addresses from certain countries.
The RPi can also do the heartbeat, and make the proxy server software emit a useful message when it fails.
The Pi can also be used to add other things by adding a software defined radio.
I’m sort of tempted to see if I can find a suitable satphone on ebay…
On the problems with tcp, while it would take significantly more hacking, with the aid of a server at home you could design something that used UDP to fetch the data instead, with an ordering/retransmit method more suitable for high latency connections, although this is now turning into more serious development.
Exactly…
Nothing on Ebay right now. I sold two 7100s on there recently, about 150 quid each. The last one went with a complete vehicle kit, car holder, antenna, etc.
Has anyone discussed:
if already discussed, i would be happy for links to those threads :)
Jonas
