plustek: Parport communication issues
Subject:
Re: Parport communication issues
From:
"Jaeger, Gerhard" ####@####.####
Date:
8 Jun 2001 06:42:25 -0000
Message-Id: <01060808472403.00684@gja>
Hi there,
let me try to enligthen you!
There are a few things to know about the Plustek parport scanners and
the driver:
All the devices using the ASIC 96001 and 96003 (Optic Pro 4800, 4831, 9630...)
have the problem, that these ASICs did have a one byte fifo.
This means, that a driver or a program MUST poll the port to get each data.
As you can imagine, if you loose only one byte of image data, the picture
will be corrupted. There's no way to recover this, as it is not possible to
detect the loss. While scanning, the driver also has to control the motor.
The ASIC 98001 and 98003 based models (OP 9636T, 12000T and PT12/P12)
has the possibility to check if we got all data. If not, the CCD module will be
moved backwards and the lines will be scanned again.
If you have a copy of that crapy Redmond system on your computer, you
might download the original Plustek drivers and you will see, that the older
scanners (OP4800...) will freeze Windoze during the scan process.
This is the data loss stuff.
The other thing is the parport mode stuff:
In the first versions of the driver I tried to detect the capabilities of the
parport on my own. Then sometimes last year I decided to use the parport module
of the Linux kernel to get all the information I need BUT I didn't want to use
the routines for accessing the port, as this is a lot of work to implement...
Now the trouble starts. The ASICs seems to be timing sensitive. You have to play
around with delays etc. Then it seems, that the IO chipsets often use special
code to switch the different modes. The other thing is the newly introduced
IEEE1248 stuff. The mixture of this causes new work for me, as I now have to
rebuild the driver.
If I have the time, I want to play around with different chipsets and scanners
to se how to make them work more reliable in EPP mode. Time is a problem
these days for me and I'm also working on the port for the USB scanners...
In general, you should try to make them work in EPP mode to obtain the best
results. One of the main problems I have now is the VIA chipset. Currently I
couldn't get it to work in EPP mode with the PT12.
That's it for now
Gerhard
