[Coco] Internet via Coco

[coco wal]

On Wed, Jul 14, 2010 at 10:55 PM, James Dessart <skwirl42 at gmail.com> wrote:

> An SPI-based driver would be much easier to program than trying to fold a
> 32-byte
> address space into something reasonable for a CoCo with other cards,
> and much simpler, hardware-wise.
>
> To some extent , you still need to bit bang your spi data to the ethernet
controller , a  'much simpler, hardware-wise' solution might be relatively
slow and taxing processor wise how exactly did you plan on implementing a
coco bus to spi interface ? I assume you would like your packet data on a
10Mb/s connection at a reasonable rate , and if under os/9 , being able to
multitask as  nicely as possible.

If you are developing  say a CPLD solution that looked similar to a motorola
 SPI microcontroller interface using 3 address locations that eases
processor burden , (even better if you implemented something like QSPI) then
cool , but you're moving away from  'simple' in that respect.



> The chips that implement an actual TCP/IP stack are more expensive
> than that.


You still use the $5 chip , add a $3 PIC that will talk to it and compile
the free tcp/ip stack microchip offers for there range of microcontrollers.
Add a $4-5 6551 or (16450) , some decode logic and link this to your PIC . I
dont think the price difference between this solution and your CPLD solution
is going to set you broke. You send serial commands to the 6551 , which are
interpreted by you PIC  , these commands are high level and take advantage
of the tcp/ip implementation on the PIC. Yes it's cool to do it all at a
lower level but I wonder how realistic it would be to implement considering
the constraints you are working with ? My experience is that you really do
need a fair chuck of memory to implement a 'decent' stack and applications ,
i'm not sure how this would all fit under OS/9 for example , others might
like to comment.


> The $5 chip I was talking about is just a plain, old
> ethernet chip, just like you would find in a network card on a PC.
>
> You mentioned a SPI driver ,so I assumed you were talking about using a
enc28j60,  PC ethernet chips are generally bus based so i'm confused ,
wasn't that your 32 byte memory problem ?