Retromaster’s Electronics Projects

…related to old computers and other assorted stuff…

UFE ADF Read Emulation Working

Posted by retromaster on May 10, 2010

UFE firmware development is going strong. Now, floppy read emulation and on-board MFM encoding of ADF files work. The ADF file chosen by the user is loaded from the SD Card and converted on-the-fly to MFM and results are written to SDRAM, from where the floppy data is served. This is in contrast to the original TFE/TFE+, for which the ADFs had to be converted on the PC beforehand. Thanks to the raw speed of the PIC32, the loading and conversion process takes about 3 seconds.  There is still room for improvement there, but I’ve decided to move on to implementing write emulation before focusing on that.

Since I haven’t built the Amiga keyboard control daughterboard yet, I’ve hooked up a few buttons to the interface connector so that I can control the user interface during testing. I’ve also disconnected the clock input from the host system and tried using the built-in oscillator of the PIC32, which seems to have worked fine. This also has the nice side effect of a slight increase in PIC32 speed.

Now that the basic functionality has started to come together, I’ve also started making notes about the changes for the next PCB revision. Here is the current list:

  1. Checkout the general purpose PIC32 variants, as the USB versions are not really required here.
  2. Remove the host clock input, as it does not seem to be absolutely necessary.
  3. Add standalone video output capability (as opposed to overlay-only).
  4. Better allocation of SDRAM lines to PIC32 pins, to increase SDRAM throughput slightly.
  5. Rework the placement of interface and programming connectors.

Also, now that I’ve tested to SDRAM code quite a bit and got it to work in a real situation, I am soon going to release source code for the SDRAM interface in the hope that it can be useful to others.

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