[Paparazzi-devel] Armel Port 2

[Gareth Roberts]

Thankyou for your responses everybody!

@ Felix - I was concerned too, but I think having used it over an SSH for
warded link from my laptop, it actually looks pretty good!  Certainly 
there is nothing that can't be sorted by fiddling with the GCS layout 
file a bit.
If anyone wants to see a picture, there is one here:
http://dl.getdropbox.com/u/169934/DSC00524.JPG

@John - my fears exactly, which is why I am initially compiling for 
"turbo easy debian" (basically debian lenny armel in an ext2 loopmounted 
file with some chroot'y tricks).  This gives me both the space and the 
precompiled library debs to compile stuff.  I have a cunning plan to try 
and then compile it either as a static binary, or to run it straight out 
of a chroot (slightly trickier install, but we are looking at a complex 
autopilot system here, so high barrier to entry).
I'm doing this for the same reasons you are - my laptop sucks and I 
can't afford a new battery.  Oh, and it's lighter/smaller/cooler.  And 
touchscreen.
I wasn't going that cool with the bluetooth thing, currently I plan to 
pop the usb into host mode (like I do for pen drives) and run my XBee 
dev board straight off it (dev board has batteries, and a bog standard 
usb --> serial convertor (the one paparazzi recommend)).  Apparently the 
standard n-series kernel has the driver compiled in.

@Paul
I agree entirely.  I'm cheating slightly toolchainwise, as I am building 
off debian lenny, so it's just adjusting the makefiles and compiling and 
packaging the none debian dependancies (or the debian dependancies that 
don't exist on armel).  The wireless data link is an idea, but I could 
just run GCS over a forwarded SSH link then, I'd rather eliminate the 
laptop completely.
It's not brilliant for compiling, but not as bad as I thought, just 
takes a bit of patience.  Annoyingly there isn't a native ocaml compiler 
for arm(el), which means I can't just crosscompile a static binary on 
i386 (my original baldrick style cunning plan).
As for the GPS, I have some idea.  I've written a python/gstreamer app 
(it's not ocaml, so sue me) which displays the video feed and overlays 
data about altitude, speed, position, battery etc for our pilot, in case 
it all goes horribly wrong on auto. 
One of the brilliant things about Paparazzi is that it uses ivy, an 
interprocess comms bus which anything can listen on.  Messages are sent 
as strings, and you use regexps to subscribe to the ones that interest you.
It uses ivy-python, you can use the example ivy-shell.py given in the 
package to work out what regexps apply to each message type (for 
example, altitude etc).  The best thing to do is switch on "messages" in 
gcs - this should flood ivy-shell with a load of subscriptions from 
which you can pick the ones you want.  It's not too bad at all really.  
Just have to be careful if you are using pygtk, as the event loops 
interact in strange ways.  You need to use a gtk.gdk.threads_init() just 
before your main gtk.main call or ivy won't work (it won't give any 
errors, you just get no messages).  I can email the whole code if you 
are interested, it's only ~200 lines.

Thanks for your positive responses, and I'll keep everyone posted!
G