Re: CB2xx RT-linux driver

[Tom Droege <droege@FNAL.GOV>]

I am quite confused about what is being discussed here.  Not
up to the software talk.  

Just so you can all think about it, here is how the Mark IV works.

1) There is a program to run which is time sensitive.  It worries
about opening and closing the shutter, and moving the camera to
the proper position for the next exposure.  At the end of an 
exposure, it sends a single command (after closing the shutter)
to the camera electronics which causes the camera to dump it's
image into the special memory card that is resident in the PC.
Once this process is started, the program can go about getting
ready for the next exposure.  Before opening the shutter, it 
must make sure that the read out process is done.  It determines
this by checking a status register.  Once the status comes up,
the next exposure can be started with it's length determined 
by your favorite timing scheme.  Before starting the next dump
into the memory card, the program must determine that the last
unload has completed.  

2) A second process does not (particularly) have to know about
time.  It just has to know that there is an event in memory.  When
it finds an event in memory it must unload it a byte at a time.
The data from the four cameras will be 0 Hi Byte, 1 Hi Byte, 2 Hi
Byte, 3 Hi Byte, 0 Lo Byte, ...  working through the pixels, so
some formatting is required during unload (or later).  There is
no multi-event buffering.  It is not possible to read out a 
particular location in memory other than by setting the address
register to 0 and reading bytes until you get to the one you 
want.  It is expected that this process will read out the data
and put it somewhere.  It will then clear the status bit that 
was set by the first process loading the memory.  The first 
process can know this by checking the status bit.  

Some useful numbers.  It takes 40 seconds to read out 1-4 cameras.
4 cameras just produce more data.  There is an ADC for each 
camera, and one can transmit bytes much faster than the ADC can convert.  
A typical exposure will take 200 to 500 seconds.  During the 40
second read out time, the camera has to be repositioned.  Plenty
of time for this.  During the exposure, say 200 seconds, one must
read out up to 32 MBytes and put it somewhere.  I think this 
should not be too hard with a not to old computer.  Somewhere,
I think, can be another computer over a cheap Ethernet link.  

I see no reason why we should not use a whole computer just to
mind the camera, read out the data, and send it to another
computer where you do serious things.  A quad Mark IV will cost
$10-15,000 to build and would have a commercial cost of order
$100,000.00  Why not devote a computer to this task and not 
try to design stuff at great cost that can be bought for $29.95
+last year's computer?

Sorry if I am confused about what the problem is.

Tom Droege