[{"element_type":"text","content":"\n  \n  \n  \n  \n  \n        \u003cp\u003eThe Xerox 820 CP/M computer could interface with dual 8\" floppy drives (or up to 4 5.25\" drives!).\u003c/p\u003e\n\u003cp\u003eWhile I did have a working pair of drives, I wanted the ability to run my 820 off of a floppy emulator. I picked a \"\u003ca href=\"https://github.com/keirf/flashfloppy/wiki/Gotek-Models\"\u003eGotek\u003c/a\u003e\" branded floppy emulator with the open source \u003ca href=\"https://github.com/keirf/flashfloppy/wiki/IMG.CFG-Configuration-File\"\u003eFlash Floppy firmware\u003c/a\u003e.\u003c/p\u003e\n\u003cp\u003eThe Xerox has a bespoke 37-pin D-style connector for its floppy drives, so I created a passive adapter PCB.\u003c/p\u003e\n\u003cp\u003eAfter configuring Flash Floppy and loading up a CP/M disk image I was able to boot to CP/M without the pair of incredibly loud drives spinning in the background.\u003c/p\u003e\n\u003cp\u003eThe \"mod\" section was for bodges but it turned out no bodge wires were needed. (it's not a header for a 2nd drive, sadly)\u003c/p\u003e\n\u003cp\u003eThe gotek's default \"S1\" jumper position is for the CP/M \"B\" drive and the \"S0\" position is for the CP/M \"A\" drive, so most of the time you'll want to move the gotek's selection jumper to the \"S0\" position.\u003c/p\u003e\n      \n\n\n\n\n","metadata":{}},{"element_type":"user_image","content":"https://cdn-learn.adafruit.com/user_assets/assets/000/000/838/original/ksnip_20240424-173400.png?1713998118","metadata":{"caption":"Kicad rendering of the board"}},{"element_type":"user_image","content":"https://cdn-learn.adafruit.com/user_assets/assets/000/000/839/original/ksnip_20240424-173234.png?1713998105","metadata":{"caption":"Kicad schematic of the board"}},{"element_type":"text","content":"\n  \n  \n        \u003cp\u003eYou can grab the kicad design files from my \u003ca href=\"https://github.com/jepler/xerox-820/tree/main/gotek-adapter\"\u003exerox 820 repository on github\u003c/a\u003e. A \u003ca href=\"https://github.com/jepler/xerox-820/blob/main/disk-images/xerox-820-boot.img\"\u003ebootable CP/M image\u003c/a\u003e is also in the repo\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHere's the content of ff.cfg:\u003c/p\u003e\n      \n\n","metadata":{}},{"element_type":"code","content":"interface=shugart\npin02=high  # 8/5 select - low is 5.25\"\npin34=low # nrdy but flashfloppy doesn't assert it early enough\ndisplay-type=oled128x64-rotate-narrow-inverse\nside-select-glitch-filter = 50\ntrack-change = instant\nwrite-drain = instant\nindex-suppression = no\nhead-settle-ms = 10\nmotor-delay = ignore\nchgrst = step\nejected-on-startup = no\nimage-on-startup = init\ndisplay-probe-ms = 0","metadata":{"language":"auto","linenums":false}},{"element_type":"text","content":"\n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n  \n        \u003cp\u003eAnd here's img.cfg:\u003c/p\u003e\n      \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n","metadata":{}},{"element_type":"code","content":"[::256256] # Std 8\" SS/SD\ncyls = 77\nheads = 1\nrpm = 360\ngap3 = 42\ninterleave = 1\nbps = 128     \nsecs = 26\nmode = fm\nid = 1\nrate = 250","metadata":{"language":"auto","linenums":false}},{"element_type":"text","content":"\n  \n  \n  \n  \n  \n  \n  \n  \n  \n        \u003cp\u003ePower the gotek adapter from the 4-pin cable and plug the 34-pin IDC cable into both devices, observing the pin 1 location.\u003c/p\u003e\n\u003cp\u003eAt this time, it's not possible to emulate a 2nd floppy drive with a single gotek with flashfloppy.\u003c/p\u003e\n\u003cp\u003eIt's probably possible to emulate the 5.25\" drive as well, but I didn't test this as I didn't have any 5.25\" floppy images. As far as I know, 5.25 drives use 500kHz FM recording mode. Note that ready and data lines get different processing for 5.25\" vs 8\" drives so other changes besides the image.cfg and pin02 state may be needed. (this is done by IC U107 on sheet 5 of the schematic)\u003c/p\u003e\n      \n\n\n\n\n\n\n\n\n","metadata":{}},{"element_type":"parts","content":"\u003cdiv class=\"parts-details\"\u003e\u003cdiv\u003e\n\u003cspan class=\"select2 parts-quantity\"\u003e1\u003c/span\u003e\u003cspan\u003e x \u003c/span\u003e\u003ca href=\"https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/171826-4/2187786\" class=\"parts-name\"\u003eFloppy power connector\u003c/a\u003e\u003cdiv class=\"parts-description\"\u003eCONN HEADER R/A 4POS 2.5MM  171826-4\u003c/div\u003e\n\u003c/div\u003e\u003c/div\u003e\n\u003cdiv class=\"parts-action\"\u003e\u003cdiv\u003e\u003ca href=\"https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/171826-4/2187786\" class=\"parts-url btn-secondary\"\u003eBuy Now\u003c/a\u003e\u003c/div\u003e\u003c/div\u003e\n\u003cdiv class=\"clearfix\"\u003e\u003c/div\u003e","metadata":{"name":"Floppy power connector","url":"https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/171826-4/2187786","description":"CONN HEADER R/A 4POS 2.5MM  171826-4","quantity":"1"}},{"element_type":"parts","content":"\n  \u003cdiv class=\"parts-details\"\u003e\n    \u003cdiv\u003e\n      \u003cspan class=\"parts-quantity\"\u003e1\u003c/span\u003e\u003cspan\u003e x \u003c/span\u003e\n        \u003ca href=\"https://www.digikey.com/en/products/detail/edac-inc/621-037-260-013/1298541\" class=\"parts-name\" target=\"_blank\"\u003eXerox floppy connector\u003c/a\u003e\n      \u003cdiv class=\"parts-description\"\u003eCONN D SUB PLUG 37POS R/A .318 621-037-260-013\u003c/div\u003e\n    \u003c/div\u003e\n  \u003c/div\u003e\n  \u003cdiv class=\"parts-action\"\u003e\n  \u003cdiv\u003e\n      \u003ca href=\"https://www.digikey.com/en/products/detail/edac-inc/621-037-260-013/1298541\" class=\"parts-url btn-secondary\" target=\"_blank\"\u003eBuy Now\u003c/a\u003e\n\n  \u003c/div\u003e\n\u003c/div\u003e\n\n  \u003cdiv class=\"clearfix\"\u003e\u003c/div\u003e\n","metadata":{"name":"Xerox floppy connector","url":"https://www.digikey.com/en/products/detail/edac-inc/621-037-260-013/1298541","description":"CONN D SUB PLUG 37POS R/A .318 621-037-260-013","quantity":"1"}},{"element_type":"parts","content":"\n  \u003cdiv class=\"parts-details\"\u003e\n    \u003cdiv\u003e\n      \u003cspan class=\"parts-quantity\"\u003e1\u003c/span\u003e\u003cspan\u003e x \u003c/span\u003e\n        \u003ca href=\"https://www.adafruit.com/product/1541\" class=\"parts-name\" target=\"_blank\"\u003eRight angle header\u003c/a\u003e\n      \u003cdiv class=\"parts-description\"\u003eBreak-away 0.1\" 2x36-pin strip right-angle male header (5 pack)\u003c/div\u003e\n    \u003c/div\u003e\n  \u003c/div\u003e\n  \u003cdiv class=\"parts-action\"\u003e\n  \u003cdiv\u003e\n        \u003ca id=\"1541-product\" class=\"product-buy btn-primary parts-url\" target=\"_blank\" href=\"https://www.adafruit.com/product/1541\"\u003eAdd  to Cart\u003c/a\u003e\n\n\n  \u003c/div\u003e\n\u003c/div\u003e\n\n  \u003cdiv class=\"clearfix\"\u003e\u003c/div\u003e\n","metadata":{"name":"Right angle header","url":"https://www.adafruit.com/product/1541","description":"Break-away 0.1\" 2x36-pin strip right-angle male header (5 pack)","quantity":"1","featured":false}}]