[Coco] DriveWire survey

[CoCoList for Color Computer Enthusiasts]

On May 11, 2014 2:53 AM, "CoCoList for Color Computer Enthusiasts" <
coco at maltedmedia.com> wrote:
>
> On 5/11/2014 1:19 AM, CoCoList for Color Computer Enthusiasts wrote:
>>
>>
>>
>> There were/are all those plus some sound devices, x10 controller, weird
>> drawing pad thing called xpad, probably more.  If its important I'm sure
>> there is a comprehensive list somewhere.
>
> Well, I'd only be interested in the biggies.
>
>>
>> Something that severely limits us with DriveWire now is that the
bitbanger
>> serial port must be polled for input, and doing that at 115kbps requires
>> 100% CPU with interrupts masked.  This has the consequence that all I/o
has
>> to be initiated by the coco, no way for the server to tell the coco when
>> data is coming in.  The DW driver has to constantly poll the server to
make
>> bidirectional I/o work.  It tries to adapt in real time to be efficient
but
>> its just not a good situation. If there was a buffer/UART on your device
>> and it could raise the interrupt line when ready, that would open the
door
>> to vastly improved performance.
>
>
> Looks like the CD line can trigger an IRQ.  Is that what you were
thinking  Buffer some bytes in a uC, trigger the Coco, and it asks for the
data?
>
> Or, are you suggesting a cartridge that will IRQ when there is data to
receive?

More the latter.  I think there is an issue with the interrupt that CD on
the bitbanger can trigger that makes it not suitable, but I don't know the
exact details.  Unfortunately I am not very well versed in the hardware.

>
> Was there an official UART cart and is the schematic available anywhere?

Yep, it was called the Deluxe RS232 Pak.  Manual is here
ftp://ftp.maltedmedia.com/coco/MANUALS/Hardware/Deluxe%20RS-232%20Program%20Pak%20Operation%20Manual%20for%20the%20TRS-80%20Color%20Computer(1983)(Tandy%20Corporation)(EN).pdf

It doesn't have schematic but does have some info about the pins on the
cartridge,dunno if that helps.  Somebody on the list might know where more
info lives if its around anywhere.