We have a Phillips SAA7111 Video Input chip connected to a
CT69030 graphics controller. To access the SAA7111 we have to use
the GPIO Pins of the CT69030, which are controlled using the
VGA registers at 0x3d6 and 0x3d7.
We can access those registers (using mmap_device_io etc.) as long
as Photon isn’t running. As soon as Photon is started, we just see
0xFF on those registers!
How can we regain access to those registers??
Oliver Dreer
news@dreer.ch
When you start Photon the graphics driver takes control
of the VGA IO ports. The C&T chipsets allow alternate access
to the VGA registers through memory-mapped registers, which
may allow you to program the registers you require.
See chapter 5 in the 69030 databook, specifically the I/O and
Sub-Addressed Register Map.
Hopefully this may provide a solution to your problem.
Oliver <news@dreer.ch> wrote:
: We have a Phillips SAA7111 Video Input chip connected to a
: CT69030 graphics controller. To access the SAA7111 we have to use
: the GPIO Pins of the CT69030, which are controlled using the
: VGA registers at 0x3d6 and 0x3d7.
: We can access those registers (using mmap_device_io etc.) as long
: as Photon isn’t running. As soon as Photon is started, we just see
: 0xFF on those registers!
: How can we regain access to those registers??
: Oliver Dreer
: news@dreer.ch