[Coco] [coco3] upscan video converter

[jdaggett at gate.net]

Roy

If you are intending throwing this out to review, then I have some questions. 

1) The block diagram seems a bit unclear. It looks as if all the COCO 3 RGB signals 
go to the ISC523 and that appears unlikely. 

2) I am a bit confused on the outputs comparator and signal translation box. I 
believe that you are doing some form a level translation of the COCO signals to that 
needed by the Averlogic AL875 part. Is there some I2C control lof this circuit? 

3) the ICS523 part supplies the video clock as well as the 2x clock required by the 
AL875. Was this part chosen because of its versitility? Does it offer a space savings 
in board lay out over a discrete crystal and divder logic? 

I understand the need for the microcontroller to interface to the I2C bus. I remember 
from the previos thread that trrying to control I2C via the COCO is a bit difficult. I 
still wonder if there is some provision for In Circuit Programing of the Atmel part? It 
does appear to be that this is just not a upscan converter but able to utilize the 
Averlogic parts more of their capabilities. 

Interesting though. I wonder how large the board will be. Yes you are pretty much 
restricted to supplying a wall wart of some kind or at least the user will. Unless the 
board is plugged into the expansion slot of the MPI,  I see no real clean way of 
getting power from the COCO. 

james 

On 16 Jul 2005 at 1:26, RJRTTY at aol.com wrote:

From:           	RJRTTY at aol.com
Date sent:      	Sat, 16 Jul 2005 01:26:56 EDT
To:             	coco at maltedmedia.com
Subject:        	[Coco] [coco3]  upscan video converter
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> 
>        Attached is a diagram of  the basic configuration for the
>        upscan
> converter I'm building and I present it here for your
> approval/rejection/ vilification/ridicule/etc... given the recent
> flame activity on the list lately I'm hoping for the best.  :)
> 
>         The converter will consist of the Avelogic AL875  high speed
> ADC to digitize the RGB video output of the coco3.   From there, the
> digital video is input to the Averlogic AL250 upscan converter. This
> will transform the digital signal back into an analog video signal
> with a scan frequency of 31 Khz compatible with all SVGA capable
> monitors.     The board signals will be line locked with an ICS1523
> programmable video clock synthesizer and line delay.
> 
>        On board programming functions will be performed by the
> ATMEL ATtiny12 microcontroller.    The three above video
> chips are programmable via an I2C interface.  The ATtiny12
> microcontroller will be programmed itself to interact with
> the I2C bus.
>         One function of the ATtiny12 will be hardware and
> power up resets.    Whenever there is a hardware reset, the
> microcontroller will set the registers of the three video chips to
> coco3 specific default values.    The converter will do a hardware
> reset with the push of the reset button on the enclosure or when
> directed to do so by software command on the I2C bus. A power up reset
> will also result in having all registers either set to coco3 specific
> default values or to a list of programmable values depending on the
> choice of the user on power being initially applied to the converter.
> A "simulated" power up can be also be performed by software command on
> the I2C bus.
> 
>         Another function of the controller includes a software
>         controlled
> standby power down of the monitor.
> 
>          I have sent a proto type of the converter to Torsten Dittel
>          for
> evaluation of the Averlogic video chips and use with PAL systems. The
> use of the coco3 RGB video cable to transmit I2C signals was his idea
> and represents a great contribution to the project.    The use of the
> ATMEL ATtiny12 controller was also the idea of someone on this list
> tho I cant remember thier name at the moment.  Sorry.
> 
>         One regret I have is I could not find a way to power the
> converter without using a wall-wart that did not involve opening the
> coco3 enclosure and modifying the motherboard.   Also, I have
> constructed the input cable with the audio signal enabled.   This
> means I will provide a sound output port on the converter.   Should I
> include an amplifier and speaker?
>          Someone also suggested I provide an output port for the I2C
> bus in the converter for use with  external I2C devices.    Is there
> any interest in this?
> 
>          So there it is.     Maybe somebody knows something I have
> missed.      If so, let's hear it.    I have become quiet proficient
> at using the PC board software I got from the PCB manufacturer so I
> expect to come up with a more compact and cost effective design this
> time around. All tho my first try at it was good enough to evaluate
> the concept.
> 
>          One more thing.     What do we call this device.    Anybody
>          got a 
> catchy name?
> 
> Roy
> 
> PS   sorry about using zip file.    Picture was too big as bmp
> to post without Dennis' help.....
>