Re: Programming graphic systems

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Olivier Scalbert wrote on comp.lang.ada:
> When playing with my GPS, I was thinking of the beautiful graphic
> systems used in safety critical environment (medical, aircraft, ATC, ...).
> I assume lots of them must be written in Ada. I was asking myself how
> are they programmed mainly at the graphic level. Does the application
> part use a graphic toolkit provided by the graphic board manufacturer or
> do you have to program all the graphic primitives yourself in Ada (as
> Bresenham line algorithm, ...) and written to the raster memory (which
> must be very cool!) ?

Until a couple of years ago, I used to work for Barco avionics [1,2]
and indeed most of our devices were programmed in Ada. We wrote our
own display drivers in Ada; they worked by writing into the graphics
processor's registers over PCI and I2C.  For bitmaps and video, we
would write into a RAM buffer then point the graphics board to the
buffer (i.e. write the address of the buffer in a register of the
board).  However, to draw the geometrical symbols for the flight
instruments, we would of course use the hardware primitives rather
than reimplement them in software.  After writing a command and
parameters in a set of registers, we would wait for a completion flag
to become true in another register.

[1] http://www.barco.com/aerospace
[2] http://www.cs.kuleuven.ac.be/~dirk/ada-belgium/events/07/070612-abga.html

For air (or rail, or seaport) traffic control, Barco also offers
2048x2048-pixel liquid crystal displays with an X server embedded in
them.  I didn't work in that division so I can't provide any more
details.

Nowadays I work in air traffic flow management [3] and we use an in-
house binding to Motif for older screens and GtkAda for newer ones.
ETFMS is a mission-critical, soft-real-time, distributed application.
It is neither life-critical (i.e. nobody dies if it crashes) nor
embedded (i.e. no DO-178B certification is needed) and the real-time
requirements are in seconds, not micro- or nanoseconds, so we can use
mainstream graphical subsystems (i.e. X11 on "normal" workstations and
servers).

[3] http://www.cfmu.eurocontrol.int/cfmu/public/standard_page/developments_etfms_index.html

--
Ludovic Brenta.