Justin England wrote:
"sicklittlemonkey" wrote ...Justin England wrote:Second topic, disk transfer from a Windoze PC to A2 disks. Since there isno 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.Short answer: voltage/current and timing, IIRC. The magic box would be an Apple II. I don't mean to burst your bubble or anything, but if you search c.s.a2 on Google Groups you'll find it's been discussed before.What voltage / current issues would there be? Most everything that I have seen about controlling a Disk ][ is done with TTL level signals. Timing issues can easily be accomplished with a PIC and some asm / C code. The only voltage / current issue I can find would get getting +/- 12V for the drive motor, as a 12V signal is not found on the USB port. An external power supply may be needed since I can only get 5V at 500mA out of the USB port.
And for "original" drives, you'll also need a negative voltage (at low current). When I attempted something like this in the early 1990s, I was planning on connecting the drive to the PC parallel port, and bit-banging the controller functions with the PC (I know I'd have had to disable interrupts and otherwise make the (at the time) 486 deterministic). I used an external power supply of the "brick on a rope" variety to supply +5v and +12v, and a small DC-to-DC converter for -5v (IIRC). My plan was derailed when I discovered that even the fastest PC processor couldn't twiddle the parallel port (or any other "legacy" I/O) any faster than about 500kHz--not fast enough to decode disk data directly. -michael NadaNet networking for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."