Saturday, January 5, 2013

Initial Schematic and Hardware

Here is the schematic that I have been working on for the past week, and my first attempt to breadboard the input portion so I can read the head control ("phase") lines. I already noticed some problems. The FTDI UM232H is master SPI only, and I drew up the schematic as a master also. I already fixed it on the breadboard. Also, I eventually need some 3-state outputs on the disk and SPI bus. Finally, I have not settled on the 74LS192 counter. I chose it because I thought I could get away without a NOT gate, but I realized I needed one anyway (the 74LS04N). A 74LS161 counter is probably more readily available (4 of them in an Apple II even), and can do everything I need. Since my last post I discovered that there are not one, but two enable lines in the DB-19 connector, so this has been accounted for. The cable is from an old 5.25" Unidisk. DB-19 connectors are very hard to find.

As for the software, I have compiled and am experimenting with libftdispi and libmpsse (which appears more complete). Unfortunately, I am not having much luck with either of them past identifying and initializing the UM232H. Both of these require libftdi which requires libusb. Using these libraries should make the program very easy or trivial to port to other platforms.

Initial SchematicInitial Assembly - Left to right: UM232H, 74LS259, 74LS192, 74LS04, 74LS15, Unidisk cable

1 comment:

  1. DB19 connectors at $2.60 each: