open1541

[skoe]

Version: 0.1
Status: Alpha
License: GPL
Download: http://bitbucket.org/skoe/open1541

open1541 is a compatible replacement for a Commodore 1541 disk drive. It uses SD cards as storage media and runs on an inexpensive hardware.
Unlike disk drives of many other systems the 1541 is a complete computer: It has a CPU which runs a DOS from a 16 KiByte ROM, it has 2 KiByte RAM and I/O chips with timers. The whole disk drive must be emulated very accurately to get a very high compatibility to the original drive. Especially the CPU MOS 6502 and the interface IC MOS 6522 must be emulated cycle exact. Also the emulated mechanics must provide correct behavior, e.g. the correct rotation speed. This all including the FAT library (12/16/32, long file names) fits into an XS1-L1 - not an easy job :)
An LCD and four buttons can be used to select, attach and detach disk images which are contained on the SD card. The custom board is optimized to be soldered manually.
Current state: The drive is emulated accurately enough to run the original DOS and many software fast loaders. The CPU and bus timing is 100% correct already (except some bugs and illegal opcodes). Many VIA registers are not fully implemented. The LCD and buttons are not used currently, a CLI over UART is the current replacement.
Current state:

Remark: The video is preliminary (work in progress). We hope we can make a better one soon. You can see there how the XMOS software is loaded via our UART boot loader into the device. Then two different disk images from the SD card are attached and their directory is shown on a real C64.
The software can be loaded from the built-in flash too, but for development we use the UART-way. Currently the disks are attached over a UART command line interfaces. But there'll be a file browser which will be controlled over the four buttons soon. btw: The case is a 2,60 Euro box from Conrad :)
Video:

Images:

[jason]

Hey there, we have just had a question on twitter:

"Do you know if this plugs into cartridge or serial port?"

Care to enlighten? Cheers.

[skoe]

Thanks, Jason. I'm not on Twitter, would be nice if you could forward the response: It's connected to the serial port just like the original 1541. Unlike the famous 1541U the Easy41 keeps the Expansion Port free in any case and therefore it can also be used for Commodore computers which don't have that port.

[jason]

Sure shall let you know or keep an eye on: http://twitter.com/duhproject tweets

[jason]

His reply is:

"That sounds awesome. And it will also work with cartridges like MSSIAH. That's good news! Thanks!"

[wardy]

I have written FAT, NTFS and HFS/HFS+ parsers in the past. If you'd like any advice or have any questions regarding FAT, I'd be more than happy to help.

[skoe]

I'll ask you when I have a problem with the FAT-stuff.

[williamk]

Just curious, where you got your plexy frame? Thanks.

[skoe]

from http://www.conrad.de/ce/de/product/8166 ... MM/1514010