Re: Virtual serial drive

[Michael J. Mahon <mjmahon@aol.com>]

Kevin <kevin@hackaday.com> wrote:
> On Tuesday, October 2, 2012 3:47:25 AM UTC-5, Michael J. Mahon wrote:
>> Kevin <kevin@hackaday.com> wrote:
>> 
>>> I have a almost working model of the host on a AVR + SD card +
>> 
>>> breadboard, its all talking, its agreeing on the cheksum, its almost
>> 
>>> reading but I only get an hour or two here and there.
>> 
>>> 
>> 
>>> but for a sanity check its all looking pretty good, get all the software
>> 
>>> going, work out the details, spin a board, and have a virtual serial
>> 
>>> drive backpacked, free of pc tether, on my //c before November
>> 
>>> 
>> 
>>> as I get things more worked out I will start publishing stuff, right now
>> 
>>> its just a ball o wires and some horrid brute force code.
>> 
>> 
>> 
>> You certainly have my interest!
>> 
>> 
>> 
>> Sounds like a great way to get a 115kb connection to an SD "hard disk" with
>> 
>> a IIc+. ;-)
>> 
>> 
>> 
>> -michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon
> 
> Well thats a bit more incentive to do it =) few things keep mulling in my
> head, maybe since you were silly enough to show interest you could chime in.

;-)

> Power: how am I going to get sufficient power to the thing, SD spec calls
> out for 200mA, and while I know no modern card living in the back of a
> apple II is going to eat that much, its not going to stop someone from
> popping in a 12 year old 32 meg card that might. Simple wall wart would
> solve this but its another thing to plug in. 

Yes, that would be worth avoiding. 

Typical current for a modern SD card seems to be in the 40-80ma range, so
it seems like a shame to be bound by the worst case. 

>Tapping off the ports on the machine is another option, but then you have
> this thing snaking all over the place, possibly blocking off something
> useful, and connectors are not cheap compared to the rest of the board. 

Yes. Too bad that serial ports don't have power. ;-(.  Maybe a pass-through
for the joystick port... It would be nice to avoid the extra cable, but
with a IIc+ I'll need a mini-DIN port adapter anyway. 

> Clock: its trivial to plop in a RTC, and the one I am eyeballing is like
> 86 cents a pop, but it adds a layer of complexity just to set the thing
> to one's local time ... and a battery (or supercap). The thought was I
> make a utility disk that goes over "normal" serial to the AVR, or just
> leaving the date/time stamps as zero.

A utility can always send a non-standard "set clock" packet while using
standard packets to read back the time. 

An alternative to the super cap/battery is setting the time at the start of
each session--better than no time at all. 

> Multiple images: using ADT you can sneak into a file manager, remove your
> current disk, plop in a new "virtual.po" file and no one is the wiser. I
> kind of like that feature. If I make the aforementioned utility disk you
> could boot to that, set I dunno 5 slots? and when you wanted to switch
> volumes hit a button on the box. another option is have a device on the
> side with a LCD screen. That almost instantly doubles the BOM cost.
> keeping in mind that I currently have the BOM at around 20 bucks not
> counting PCB and actual card.

I'm sure some would like multiple images, but I can live very comfortably
with a 32MB disk image. ;-)

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon