Photon, VGA and real time

I have passed through a terrific problem and I would like to
post my experience:

I have a small system providing measurement from serial line
115200 bps, data are comming one package per 10ms; ticksize is 1
and reading is via dev_arm. Meassure data are stored on server
process playing role like share memory and displayed by photon
appliction in RtTrend.

At first we used VGA card S3 Trio, we had terrible flicker.

Then we used S3 Savage, there no flicker, but we detected
problems with reading from the serial line: some data was lost.
Though the reading process had higher priority than Pg driver
and displaying application. It had to be caused by Photon itself.
It was very funny, because when I switched to other console
without RtTrend, no problem with real-time was detected, even
when there was only monothone data in the trend, the lost of
data from line was only occasional.

Then we used Riva TNT2, Tornado TNT2 and even very cheap
Vanta LITE card, with all these cards we had no problems.

It seems to me that Photon behaves a little bit recklessly
to other processes. It is strange, since it is native GUI
for QNX and QNX is real-time OS.

My result: when you have operational photon and you have
appropriate refresh (and it is not too easy to get into
this state), you are still not winner.

Andy

Hi Andy,

There is a known problem with the Savage driver that affects
interrupts, which in turn affects the serial line.

Erick.


Andrej Lucny <andy@nod10.mstep> wrote:

I have passed through a terrific problem and I would like to
post my experience:

I have a small system providing measurement from serial line
115200 bps, data are comming one package per 10ms; ticksize is 1
and reading is via dev_arm. Meassure data are stored on server
process playing role like share memory and displayed by photon
appliction in RtTrend.

At first we used VGA card S3 Trio, we had terrible flicker.

Then we used S3 Savage, there no flicker, but we detected
problems with reading from the serial line: some data was lost.
Though the reading process had higher priority than Pg driver
and displaying application. It had to be caused by Photon itself.
It was very funny, because when I switched to other console
without RtTrend, no problem with real-time was detected, even
when there was only monothone data in the trend, the lost of
data from line was only occasional.

Then we used Riva TNT2, Tornado TNT2 and even very cheap
Vanta LITE card, with all these cards we had no problems.

It seems to me that Photon behaves a little bit recklessly
to other processes. It is strange, since it is native GUI
for QNX and QNX is real-time OS.

My result: when you have operational photon and you have
appropriate refresh (and it is not too easy to get into
this state), you are still not winner.

Andy