68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
FloppyEMU IDC20 Connector Pin Out Help
Posted by: mcbeav on 2024-08-07 15:32:45 Looking for some help with the pinout of the IDC20 connector on the FloppyEMU / Macintosh LC575. I am setting up a FlippyFloppy from the magical Kay Koba, but I want to use a DB19 connector instead of the IDC20 cable. This is purely for aesthetic, and completely form over function. I'll be wiring the DB19 cable to essentially just be an extension from the FloppyEMU to the FlippyFloppy connector, but I'm losing a pin because DB 19 has 1 less pin, and I'm not sure what pin I can drop from the IDC20 connector. I'm looking for some help with which pin I can drop from the IDC20 connector / which of the 20 pins can the FloppyEMU and Macintosh floppy still operate without?
Posted by: demik on 2024-08-07 15:43:23 Not sure if I understand correctly, but you may want to use the standard pinout for the DB19 cable. Here is the pinout for an IDC20 to DB19 from BMOW (https://www.bigmessowires.com/2015/04/09/more-fun-with-apple-iigs-disks/) Ignore the logic things On TashTwenty, we didn't connect the -12 line but it's overwise pinout compatible if you need a PCB that does the conversion
Posted by: mcbeav on 2024-08-07 18:18:20 Not sure if I understand correctly, but you may want to use the standard pinout for the DB19 cable. Here is the pinout for an IDC20 to DB19 from BMOW (https://www.bigmessowires.com/2015/04/09/more-fun-with-apple-iigs-disks/) Ignore the logic things On TashTwenty, we didn't connect the -12 line but it's overwise pinout compatible if you need a PCB that does the conversion So, theoretically, for connecting the FloppyEMU to a Macintosh, if pin 9 on the IDC20 connector / ribbon cable was not connected, the FloppyEMU would still work without issue?
Posted by: demik on 2024-08-08 02:02:27 Yes. The TashTwenty IDC<->DB19 adapter (so no IDC PIN9) is working just fine with Floppy Emu on a Macintosh
Posted by: cheesestraws on 2024-08-08 02:07:47 So, theoretically, for connecting the FloppyEMU to a Macintosh, if pin 9 on the IDC20 connector / ribbon cable was not connected, the FloppyEMU would still work without issue? Yes, BUT. This isn't what you have to do to get the 20 pin IDC down to 19-pin D. You should use BMOW's diagram above for the wiring for that. The fact that the floppy emu will work perfectly fine without -12V isn't the point here. You can't just randomly wire up signals to wires and expect the result to work, you have to make them turn up on the pins the hardware expects them to turn up on. Use BMOW's wiring diagram. And if you attach +12V to a random pin on the 20-pin IDC you will have a bad time and will blow something up. I'm surprised you didn't get instructions or an adapter with this, if it's pretending to be a finished product.
Posted by: mcbeav on 2024-08-08 14:58:05 Yes, BUT. This isn't what you have to do to get the 20 pin IDC down to 19-pin D. You should use BMOW's diagram above for the wiring for that. The fact that the floppy emu will work perfectly fine without -12V isn't the point here. You can't just randomly wire up signals to wires and expect the result to work, you have to make them turn up on the pins the hardware expects them to turn up on. Use BMOW's wiring diagram. And if you attach +12V to a random pin on the 20-pin IDC you will have a bad time and will blow something up. I'm surprised you didn't get instructions or an adapter with this, if it's pretending to be a finished product. What I am attempting to do isn't a finished product. I'm re-wiring a DB19 cable that has an IDC connector at one end and a DB19 connector at the other end. Yes, BUT. This isn't what you have to do to get the 20 pin IDC down to 19-pin D. You should use BMOW's diagram above for the wiring for that. The fact that the floppy emu will work perfectly fine without -12V isn't the point here. You can't just randomly wire up signals to wires and expect the result to work, you have to make them turn up on the pins the hardware expects them to turn up on. Use BMOW's wiring diagram. And if you attach +12V to a random pin on the 20-pin IDC you will have a bad time and will blow something up. I'm surprised you didn't get instructions or an adapter with this, if it's pretending to be a finished product. I don't think I probably explained this very well. I'd have to post some photos when I have a moment. This isn't any sort of product I bought. I'm using a DB19 connector and cable from an old apple ii floppy drive and rewiring it to use as an idc20 extension cable, but it's obviously missing a pin, so I'm inquiring about if there is an unused pin that can be left out and still work properly seeing as there are multiple 5V pins, multiple ground pins, and i believe i read on the BMOW that not every pin is used by the FloppyEMU
Posted by: cheesestraws on 2024-08-09 00:02:25 This isn't any sort of product I bought. I'm using a DB19 connector and cable from an old apple ii floppy drive and rewiring oh, sorry, I misunderstood: I thought you bought kind of floppy product that hadn't come with an adapter or any instructions. It wasn't a dig at you, it was a dig at half-arsed products 😀
Posted by: mcbeav on 2024-08-09 06:14:16 oh, sorry, I misunderstood: I thought you bought kind of floppy product that hadn't come with an adapter or any instructions. It wasn't a dig at you, it was a dig at half-arsed products 😀 No worries at all. I appreciate the help. Your comment got me wondering, maybe I can combine 2 of the ground signals going into the db19 connector, and then split that back out to 2 ground pins so that all 20 of the pins will be connected on both sides of the extension.
Posted by: cheesestraws on 2024-08-09 06:33:48 Yeah, all the grounds as far as I know are basically interchangeable and meant to be commoned together.
Posted by: mcbeav on 2024-08-09 09:06:41 Yeah, all the grounds as far as I know are basically interchangeable and meant to be commoned together. Awesome! Thanks for the help! I really appreciate it! That solved my issue. I can just combine the grounds and them split them back out on both sides so there are no pins missing from the idc connector. I appreciate the input big time!
1