Tuesday, 11 March 2014

Board Giveaway

I have built another PCB with improved layout and a debug pin for the logic analyzer so I am giving away my first working prototype PCB to the person who makes the best submissions. I'm looking for someone who has both a Raspberry Pi and a TRS-80 and is capable and interested in moving the project forward. Note: this is the board to read  and convert TRS-80 floppy disks to DMK format, not the floppy drive emulator.

With this board, a Raspberry Pi and a TRS-80 floppy disk drive you can rip TRS-80 floppy disks to .dmk files. Works very well with single density disks including many copy-protected disks. Double-density is a work in progress. Works fairly well for non copy-protected disks with verify enabled.

Please email submissions to me at alan.page.ca (@) gmail.com. Photos of your Pi and/or TRS-80 are encouraged. Submissions may be published on this blog, but with email addresses removed. Please indicate if there is any part of your submission you don't want published.
Prototype PCB Board
The successful applicant will receive the prototype board shown here and I will pay shipping (cheapest ground rate).

If there is sufficient interest I am willing to build a few more boards and sell them at the cost of materials plus shipping.

Current Status

DMA is working well at 5 MHZ. It is very reliable with FM decoding, marginal for MFM decoding. This appears to be the limit for getting a full track in a continuous chain of DMA blocks. For some unknown reason the DMA chain stalls out at around 128K. I can extend it by clearing the output FIFO but then there is a one microsecond gap which could cause data loss. Faster DMA speeds could be achieved by using multiple overlapping operations. For example, two 8 MHZ request chains covering 2/3 of a revolution each. I would then need to splice the two blocks together on a suitable boundary.

ZIP file of current PCB schematic/layout for KiCad
ZIP file of current source code.