too many variables

I think that’s really the problem I’ve been facing with this floppy project. Trials and tribulations indeed. Or at least trial and error, with stress on the error part. There are probably less than half-a-dozen people worldwide that have the very specific knowledge that I need to get this off the ground. These would be people from CAPS, one person who sells an amiga (as well as other floppy drives) floppy controller card, and that’s it.

I’ve talked to some really nice ex-Commodore employees who have been friendly, and helpful.

The problem, of course, is that these machines were created a long time ago. The programmers of the original OS, freeware/shareware software, hardware, have all long forgotten the details. And you know what they say, “the devil’s in the details.”

To give you an idea of the variables with which I’m working:

1. Am I reading the hardware signal right? Are there *really* only three possibilities coming out of the drive, a “10”, “100”, and a “1000”? This is all I’ve been able to observe…

2. Is the software I’ve written on the SX microcontroller properly sampling this data at the right time? I have two interrupts occuring, one for the edge detection and one for the 2us timeout which clocks a zero in (up to 3 of them in a row before going idle). So far, sometimes this works, and sometimes it doesn’t. Why and how is this getting out of sync?

3. Is the SX transmitting faster than the PC can handle this? So far, my observations say no, and I implemented a software FIFO to help out.

4. Is my software FIFO working?

5. Is my PC software, that’s designed to receive all this, working properly? I’m now storing the transmitted bytes in a memory array, and later storing to disk, to prevent any speed issues associated with accessing the hard drive.

The REAL problem here is that I simply don’t know what is actually leaving the drive in terms of data. The only thing I’ve been able to figure out is that the MORE data is leaving the drive than is showing up on the PC. This is a bad sign. Where’s the data being lost? My guess, the sampling isn’t working properly. Something is slipping. But how the heck can it slip when a transition resets it, and transition is occuring on a very regular basis (minimum every 4us, maximum every 8us). The thing only has to run freely for a few cycles.

Add the fact that the only real pattern that I can VISUALLY look for is the 0xAAAA 0xAAAA 0x4489 0x4489 raw sync sector in raw MFM. Any words, or real data has to be decoded before, properly aligned on a byte, etc. PAIN IN THE BUTT to figure out if everything is actually working. Most of my programming projects, whatever they might be, are straight-forward. Run it, see if it works, and then go back and fix it if it doesn’t. Even the indication that this thing is working is obscured.

There are so many variables, and I’m constantly changing all of them, that who knows when one part is working? Of course, you say, only change one thing at a time. OK, makes sense, but this just isn’t practical. If I change how the SX xfers to the PC, then I have to modify the PC software accordingly…. So if I make a mistake in coding on one side or the other, who knows?

Maybe I’m lacking the necessary basic project management, coding, microcontroller, hardware experience required to get this off and running?

BTW: my title of this entry reminds me of “Too many secrets” or “Cootys Rat Semen.” from Sneakers. If you don’t know what I’m talking about, please disregard! 🙂

About the author

keith

Amateur Electronics Design Engineer and Hacker