No; I didn’t bother. Too much work borrowing a GNS-W or GTN box. And Garmin are sure to have some crypto on it, which could be quite difficult or impossible to decode. The application was the generation of a “WAAS” position data stream for a bit of avionics, which accepts either the secret Garmin RS232 protocol, or an ARINC429 documented protocol. So I generated the latter, as a part of another project which emulates a KI256:
I have now nearly finished coding the GPS to ARINC429 (loads of position labels e.g. 110,111,310,311 concurrently generated – quite a learning experience!) converter and am ready to take a look at generating the Garmin RS232 stream.
If anybody has an old GNS (preferably W?) box kicking around, which I could borrow, I will take a look at what comes out of it. The RS232 stream may be encrypted, or it may just have a CRC or similar.
It probably wants to be in the UK, to minimise shipping cost and delays.
got it ;)
The Garmin RS232 data stream is probably going to be too difficult.
I have solved it using ARINC429, on which the data cannot be hidden. I am using a PCMCIA ARINC429 card from Ebay and some free software. Here it is generating Label 203 pressure altitude, at high speed just like a GTX330:
For a GPS, one can buy a WAAS/EGNOS compatible module for €20, which outputs NMEA. Then output labels 310/311 or 110/111. Or all of them 
The C coding is quite good fun, but laborious because the way each label’s data is encoded is different.
Peter wrote:
Next I need to borrow something which generates a pressure altitude and a GTX330 would be ideal. Then I will need something which outputs WAAS GPS position. Would a 430W do that?
If you like programming, you can build a raspberry pi with stratux build and some SDR and a GPS, it does get WAAS GPS, that you can find in a driver, and easily connect a USB to serial converter. Then the coding job :/
Edit: look at this:
https://github.com/neonbjb/RaspPiArinc429
Curiously the Avidyne navigators also do not output labels 110 and 111, so that connection must also use the proprietary RS232 data stream. I wonder why Avidyne did that, given that they control both ends of that connection?
Does anything out there output labels 110 and 111?
Aha that explains why I could find only labels 310 and 311 in the GNS430W IM, and only labels 110 and 111 in the TAS605A IM
One has to use RS232 for that connection, and of course that data stream is “secret”.
There might be a demand for label 310/311 to 110/111 converter 
Peter wrote:
Then I will need something which outputs WAAS GPS position. Would a 430W do that?
It does, but not in 429. It uses a Garmin RS232 protocol.
The TAS605A interfaces with a GNS430W in RS232 so presumably it’s getting it’s position data from there..
The 429 output labels from a GNS430W are as follows;
I am now successfully decoding ARINC429 coming out of a spare SG102 AHRS.
The code is messy. This is the Label 320 (mag heading) description
The label is encoded in octal but that is only a part of the fun. The bit numbering is, ahem, unusual
Next I need to borrow something which generates a pressure altitude and a GTX330 would be ideal. Then I will need something which outputs WAAS GPS position. Would a 430W do that?
I did find a PCMCIA card on Ebay in Germany for about 150 quid but could not get it to do anything, but managed to work it out anyway with the help of the SG102 data source.
The curious thing is that the TAS605A requires labels 110 and 111 for the position, but a 430W doesn’t list these in its outputs. It shows 310 and 311. So how does a 430W act as a position source for a TAS6xx over ARINC429 ?
