Re: Hardware musings

["Justin England" <justin@rapidcity.net>]

"Greg Andrzejewski" <pressyourluck85@yahoo.com> wrote in message 
m6OdnZA5F8lpia3YnZ2dnUVZ_sqdnZ2d@comcast.com">news:m6OdnZA5F8lpia3YnZ2dnUVZ_sqdnZ2d@comcast.com...
>
>>
>> A light technical overview of the project:  I did a quick scan in the 
>> last couple of days of the AppleTalk ROM listings in my //c Tech Ref 
>> book.  It appears at first glance that Apple set up the AT code in the 
>> //c to simply look like a smart port device.  Therefore, I would have to 
>> assume that ProDOS would have seen it as nothing more than another 
>> smartport.  Since the //c already has a smartport, why couldn't a device 
>> be built that connected to the smartport and talk to an AppleTalk network 
>> (via localtalk or even ethernet.)  My idea would be (mind you, I have 
>> forgotten most of what I ever knew about A2 hardware) to have something 
>> like a PIC that would receive the signals / commands from the smart port, 
>> and translate them to AT and send them down the localtalk wire.  There 
>> would also have to be some form of a CHOOSER that could talk to the PIC 
>> and could even store usernames, passwords and "shares" in NVRAM. A simple 
>> ATINIT could be written to map the "shares" to ProDOS volumes.
>>
>
> Appletalk on a IIc would be cool, but I don't think it would be worth the 
> time. Putting all that work into implementing a dead protocol doesn't make 
> sense to me. Especially since, if you have the expertise/ability to pull 
> such a project off, there are probably more worthwhile projects for you to 
> work on (IIc ethernet maybe?)
>

This seems like quite a difficult project, but seeing how the netatalk 
package is opensource, most of the code for appletalk get be garnered from 
there.  As for the hardware interface.... who knows?  Although, if possible, 
the hardware layer could be anything, I say localtalk simply for ease of 
implementing as opposed to ethernet.  Granted, one can find ethernet chips 
that are pretty self-contained, some even have an IP stack built in, so all 
that is essentially needed is to pass a block of data to the chip and it 
handles all the ugly stuff of talking down the wire.

>> Second topic, disk transfer from a Windoze PC to A2 disks.  Since there 
>> is no way to directly connect a disk ][ drive to a PC (unlike other 8 bit 
>> computer's disk drives), why couldn't a "magic" box be built that would 
>> connect a disk ][ to a USB port.  It should be fairly easy to find a USB 
>> to TTL device that could talk to a PIC, and the PIC could directly manage 
>> the drive.  On the PC side, it shouldn't need to look like nothing more 
>> than a USB to serial device, therefore a simple protocol could be 
>> developed that the PIC code could interpret and perform the necessary 
>> functions. Considering the amazing CiderPress program, it should be easy 
>> for Andy to implement a way of sending data down the USB port that 
>> includes the protocol handshake and a raw disk image (in a predefined 
>> format.)  Again, I have forgotten most of what I knew about A2 hardware, 
>> but I can't imagine it being horribly difficult to "emulate" a disk ][ 
>> controller with a PIC considering it should have to ability to do the 
>> timing critical functions.
>>
>
> This idea has been kicking around in my head for a little while, too. I 
> suggest you download a copy of "Understanding the Apple II" (search the 
> group for links) as there is a chapter that describes the disk ][ 
> operation in detail. I know this topic has come up before, so you may want 
> to dig around the archives for old threads. IIRC, even though the 
> disk ][ card is just a state machine, Apple II disk access is so timing 
> dependent that for the amount of logic it would take to duplicate it on a 
> PIC or FPGA you might as well put the whole computer on it.
>
> Smartport devices might be easier, but I don't believe there is a whole 
> lot of documentation on the protocol.
>

A smartport device would be cool, but like you said, documentation of the 
protocol is hard to come by.  Google searches don't come up with anything 
other than "read the GS rom listings."

Justin