In SX Microcontrollers, SX/B Compiler and SX-Key Tool, kmonsx wrote:

Hi all,

You guys might recall my usb external amiga floppy drive controller application from a year or so ago.  For those of you who don't know, I'm using an SX28 with Parallax's USB2SER device coupled with some memory to make a small device that lets PC users read old school amiga floppy disks to create .ADF files for archival or emulator purposes.

Although the project isn't finished, I've made good progress on it, and wanted to share the progress with those that helped.

The drive spits out raw MFM data, and the job of the SX is to read these signals as a "1" or a "0", and store them into memory for temporary storage.  The device reads and stores a track at a time.  After successfully storing a track, it waits in a command mode for a "transfer command" where the PC tells it to transfer the data via USB.  I run the USB interface at 2mbps, which the SX has no problems handling.  I actually have to slow the SX down with nop's.

I went around and around with how to read the actual data, and what ended up working the best was a two-interrupt method where an incoming falling-edge triggers the start of a group of data(a '1'), and each successive 2us timeout adds a data '0'.

The PC was simply too slow to read the 500kbps stream directly, so memory, coupled with a faster USB link did the trick.

A high-level overview can be had at [url]http://www.techtravels.org/amiga/amiga.html[/url] and the continually updated blog(including pictures) is at [url]http://www.techtravels.org/amiga/amigablog[/url].

The SX is a really nice fit for the application mainly in regards to speed, ease of programming, and features.  The USB2SER couldn't be easier to use, both from a hardware standpoint(I think I use 3 wires!), and from a windows programming perspective.

Keith

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