I have been working on the Pacsat Ground Station for FalconSat-3 in my spare time. I looked back at my notes here and realize that it was August when I last posted about this. And I have not been on the spacecraft much. It has been hard to keep WISP alive. Every time I patch Windows 10 it seems to mess up the registry settings. I need to search through it and manually remove all traces of WISP, then re-install and re-register. But in the background I have been tinkering with my own code.
The directory and file requests are mostly working. The next big challenge is uploading files...
To support uploading I have had to code an AX25 Data Link State machine, which handles connected mode. This turned out to be quite tricky. Significantly harder than the Downlink and Directory. If you have ever browsed through the AX25 specification, then you know that is quite a bit of effort. But it was fun and it is mostly working, at least with my test setup in the lab. And I have learned a lot, which is the only reason I do these things.
I've attempted many uploads to FalconSat, without success. I can't usually be in front of the computer so I have to come back and look at the log to work out what happened. Sometimes there is a bug in my logging code and then the crucial piece of information is not captured ... Ugh ...
I think I have fixed most of the issues that were preventing upload and a very short file uploaded this morning, which fitted in a single Iframe. I even managed to reply to one of my messages and upload that, which is shown in the screen shot. But a longer file has not worked. Or rather I uploaded it as file 14DF (a Pacsat gives each file a unique file id and it seems traditional to quote them in hex) but now I can't see it in the directory or download it. It seems to be corrupt. If anyone is able to download it then send me a message.
If anyone knows why FalconSat sends UA frames without the F bit to 1 when I send a SAMB frame with P=1, then let me know. I was also getting FRMR frames once I logged in and sent the first data frame, but that was because my Iframe was too long. Most recently the file was uploading but the header was being rejected. I think I fixed that this morning. When you set the new file id received from the spacecraft, you have to zero out the checksum before recalculating it. Now that is done and the short file uploads.
My hypothesis for file 14DF is that the Pacsat header is too long for a single kiss frame from the spacecraft. So it is being split across two frames. I (probably wrongly) assume that all the AX25 frames sit inside a single kiss frame. Or perhaps it is two AX25 UI frames, but again the data is split across two UI frames. That makes the most sense because I get two different error messages from different frames.
There is a new version of the ground station software if you want to test this along side me, though it is far from bug free. If you see problems then please post them on github or report them here in the comments. 73 Chris g0kla/ac2Cz
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