[Coco] Re: [Color Computer] Re: Adapter from Coo3 to SVGA

[RJRTTY at aol.com]

In a message dated 4/5/05 6:06:39 PM Eastern Daylight Time, 
Torsten at Dittel.info writes:

<< >         The coco3 has a 4.7k pullup resistor on that line........and
 > the I2C specification for the BIDIRECTIONAL data line for these chips calls
 > for a 4.7k pullup resistor .
 
 >What kind of data could the CoCo *receive* from the Chip? Is there kind 
 >of a handshake (like XON/XOFF)? Could the chip report its settings to 
 >the CoCo?
 
     The exchange of data is started  by taking the data line low when
the clock is high.     The exchange of data is terminated when the
data line is taken high while the clock is high.    This will work
without handshaking because  I2C is a synchronize interface
and the coco3 is always the master device and controls the
clock.
      Most of what we need to do is send data to the chips.
However, the coco3 can also recieve data from the chips in
order to display thier value.   At first I am going to include
just a simple activation program which only needs to write
to the video chips but later, everbody who buys a converter
will get a more complete control program with the capability
to read and change data (gamma values, timers, etc.).
I may have to seek help in this area from anybody who is
willing to devote some time to it.


 >        The only down side to this is the need to redsign the cable.
 > We will have to use an alternate plug and socket combination.
 
 >I was always planning to make an AL design which fits exaxtly in this 
 >spare place of the CoCo3's bottom and connects directly using an Flat 
 >Ribbon IDC 10-Contact Socket Connector and a *very* short cable (if 
 >necessary at all, I don't know if there's a conector which could be 
 >soldered directly to the adaptor's PCB) to optimize picture quality.
  >>
I have used a flat cable about 6 feet long to connect the coco3 to the
converter with no degradetiion of signal.  The Averlogic chips have
extremely good stability and noise rejectiion.


Roy