USB Universal Floppy Disk controller

[Dwight K. Elvey]

>From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
>
>On Mon, 2005-03-14 at 11:55 -0800, Dwight K. Elvey wrote:
>> >From: "woodelf" <bfranchuk at jetnet.ab.ca>
>> >Look what you are doing is building a generic floppy disk controler.
>> >The only high speed device what you use to sync the  data/clock pulses
>> >to the system cpu clock. The rest is software.  I'd sooner use a CPLD
>> >designed for generic bit sampling but a PIC would also work with
>> >a digital data/clock seperator. Now would getting the people who do
>> >cat-weasel create a USB version be a better goal?
>> >Ben alias woodelf
>> >PS. What about hard-sectored floppy disks, that too may  need reading
>> >too?
>> 
>> Hi
>>  I think you are missing what I am saying. The SPI is just
>> a shift register that takes an external clock. It can be programmed
>> to automatically DMA transfer into memory. It is the perfect zero
>> additional logic circuit to use. You don't need to build a
>> data/clock separator or anything. Just sample the data.
>> One could even make the output SPI provide write data. These
>> chips are designed to load their programs from a single
>> flash or EPROM so the entire hardware requirement is almost
>> nothing.
>>  I see others on comp.os.cpm talk about using a 50MHz variant
>> of a Z80. I think most miss the point. These DSP's are 30 MIPS+
>> not just 50 MHz clocks. They have enormous capabilities in
>> a relatively small package. It was like they were designed for
>> this project. You don't need to create a CPLD since the hardware
>> part is already done for you.
>
>What about cost? (irrespective of how the device physically connects to
>the host machine)
>
>I forsee four goals to make it useful:
>
>  o  Cheap

Hi
 When one considers how much hardware one saves over a PIC solution,
the DSP is cheap. They are in the $10 range.

>  o  Simple to build by anyone with a few electronics skills.

 A little tough here. 50 mil spaces surface mount. Some soldering
skills required.

>  o  Open 'source' (all schematics etc. available)

 No issue here.
 
>  o  Easy / quick connectivity

 Although, most computers come with a parallel port, using
the port on a newer XP for other than normal purposes may be a pain.

>
>Catweasel seems to lose out on 1, 3, and 4 - and 2 isn't relevant in its
>case. Can't comment on how nice its software API is as I haven't looked
>at it yet, but doubtless a bunch of us on this list could come up with
>something that'd cater for all tastes (plus the really low-level
>software would all be open source anyway!)
>
>Personally I'm not a fan of a USB version though; I'd rather have
>parallel as pretty much any machine has a parallel port - USB limits me
>to newer PCs and Macs (plus software interfacing *might* be harder). 
>
>Priorities seem to me to be (highest first):
>
>  o  Reading disks

 Should be easy.
 
>  o  Writing back a disk image

 I see only minor issues here ( pre-comp )
 
>  o  Decoding disk data on host machine

 Just requires some one to do it.
 
>  o  Modifying disk data on host machine, re-encoding back to floppy

 If one can do the above, this one comes along, almost
for free.
Later
Dwight


>
>Happily, that's probably order of complexity too, easiest first :) (I am
>coming at this from a preservation point of view, rather than being able
>to create disk images for use with emulators, say)
>
>cheers
>
>Jules
>
>