[TI-H] PIXpander source

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[TI-H] PIXpander source



I am resending this message, since the first time I sent it
I was not yet subscribed to the list; I am not sure if it
arrived:


Hi all,

I have just finished my course and now I have some free time to
continue the work on ti-calc stuff. I haven't had the time yet to
read all the messages on this list concerning the PIXpand.

Adam Thayer and Stephan Effelsberg: I have just read the emails you
sent a while ago (more than a month); Sorry for not being able
to answer you sooner...

I saw Stephan's commented de-asm; I suppose that the first thing I have
to do now it to release the original source code to make it easier to
debug.

Also, could you please list all the points you think are wrong in the
hardware? Here are some of the answers to the points I have found in
Adam's messages:

-The 5V->3.xV conversion is implemented with the 120/330 resistors and the
 3.3V zener on the power line only. I dont think that we need to add
 conversion to every input pin of the PSX card, since they should be
 5V tolerant.

-Adam: You are right about the fact that ACK is supposed to be open-drain
 the that there is no pull-up resistor on it like the one on the DAT line.
 However, when experimenting with the device I have found that removing
 the pull-up resistor from ACK created better results (haven't investigated
 on the reasons for this). Anyway, in the beta code the ACK line is not checked
 as it should be (you will see this in the source code soon).
 
-Adam: Yes, Pin 1 of the 2.5mm jack is not like pin 2, this is made so to
 save a pin on the PIC. The open-drain line on pin 1 is implemented in software.
 The same thing could be done with pin 2 and save the diode.
  

Again, this is a beta version and I know that it has many bugs (however, I was
able to succefully transfer a variable with it).


Regards,

Sami Khawam
http://sami.ticalc.org

PS. In the archive on ticalc.org I was only able to read the messages sent
    during May; Thus I dont know if Adam has released his version yet.
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