Smokeless Joe Posted June 9, 2016 Share Posted June 9, 2016 (edited) This is my very first time doing something like this, so be gentle, but constructive criticism is encouraged. I kinda boned the ExtSel mod on my 1200XL. It just seems so drastic to cut the pins off a perfectly good 74HC08. Soldering things directly to chip is also kinda unaesthetic. Also, I kinda suck at it. So I'm thinking something like this (borrowing entirely from Bob's Wooley's PBI instructions): The existing 74LS08 gets plugged into U1, which is then plugged into socket U17 on a 1200XL motherboard. An unspoiled 74HC08 gets plugged straight into U2. R1 is a 2.7K resistor, just like in Bob's instructions. J1 could be right angle or straight headers. It's really simple, and I'm sure I could use a few lessons on PCB design. Also, I don't know how much work it cuts down. You still need to: 1. Cut the trace and solder a wire to the pad above U11 (connects to J1 pin 6) 2. Solder a wire to U14 pin 16 (connects to J1 pin 1) 3. Solder a wire to +5v (connects to J1 pin 3) 4. Remove Q4 and Y1 from the motherboard But then you have J1 pin 2 for CasInh and J1 pins 4 and 5 for ExtSel (VBXE and Rapidus). A larger J1 could be added if more ExtSel and CasInh lines are needed. Waddya think, sirs? Edited June 9, 2016 by Smokeless Joe 2 Quote Link to comment Share on other sites More sharing options...
Rybags Posted June 9, 2016 Share Posted June 9, 2016 I don't have the mod instructions available but - to eliminate cutting off pins, couldn't you equally just do the same to a socket and use between chip and existing socket? So long as not too many pins are to be disconnected it should work fine and cost next to nothing. Quote Link to comment Share on other sites More sharing options...
Bryan Posted June 9, 2016 Share Posted June 9, 2016 Cutting legs on a $0.40 chip doesn't bother me. Might not be the cleanest solution, but it's not drastic. The board is a nice solution, though. 1 Quote Link to comment Share on other sites More sharing options...
Mathy Posted June 9, 2016 Share Posted June 9, 2016 Hello guys How hard would it be to add the MPD signal to the board/design? This signal is missing on the XEGS MMU. Would be nice if we could use the same board for both the 1200XL and the XEGS. Sincerely Mathy 2 Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted June 10, 2016 Author Share Posted June 10, 2016 Oo! A request! How hard would it be to add the MPD signal to the board/design? This signal is missing on the XEGS MMU. Would be nice if we could use the same board for both the 1200XL and the XEGS. That's a good question. I don't know how the MPD signal is normally added to an XEGS. Anyone know? Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2016 Share Posted June 10, 2016 I don't know how the MPD signal is normally added to an XEGS. Anyone know? You need a GAL programmed with a JED which provides an MPD signal on pin 14. Here's the JED (from Lotharek's Rapidus page): xegsmpd.zip Quote Link to comment Share on other sites More sharing options...
oracle_jedi Posted June 10, 2016 Share Posted June 10, 2016 If you make a run of these i'd be interested in buying two for when I get around to adding VBXEs to my 1200XLs. Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 10, 2016 Share Posted June 10, 2016 VCC is on pin 14, so you can route that straight to one end of pullup R1 and do away with any +5v jumper wire. Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted June 10, 2016 Author Share Posted June 10, 2016 Cool! Even one less wire is a very happy thing. Now it'll look something like this: How many 1200XL upgrades require an ExtSel or CasInh line? I only know of VBXE (one of each) and Rapidus (ExtSel). It'd be nice to make J1 practical for other/future upgrades. Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 11, 2016 Share Posted June 11, 2016 Well, I think you exhausted the current list right there. Three EXTSEL signals each with a pin to themselves will be very nice and probably adequate. My own machine completely maxed out the signal by sending it to three different locations: VBXE, PBI connector, and Rapidus, although the latter has been evicted for the time being. Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted June 16, 2016 Author Share Posted June 16, 2016 (edited) Here's my latest design. Unless anyone spots some serious errors, I'll probably submit this to OSH Park this weekend: U1 is the existing 74LS08 from socket U17 on a 1200XL U2 is a 74HC08 R1 is a 2.7K resistor J1 are pin headers If I'm interpreting Bob's instructions correctly: U2 pins 7 and 14 connect with U1 pins 7 and 14, respectively U2 pin 2 connects (via R1) to U1 pin 14 (Vcc/+5V) J1 pin 1 connects to U14 pin 16 J1 pin 2 is CasInh J1 pins 3,4,5 are ExtSel (for VBXE, Rapidus and/or a PBI connector) J1 pin 6 connects to the pad above U11 And I'll still need to cut the trace from U14 to U11 and remove Y1 and Q4. Anything else? EDIT: Huh, it's exactly like my last design only with a slightly different program. Oh well. Edited June 16, 2016 by Smokeless Joe 1 Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted June 17, 2016 Author Share Posted June 17, 2016 Printing out proofs revealed a couple quirks. Now I'm thinking something like this: This fits much better on the motherboard since there's a convenient space just above U17, with the top of the board just shy of Q14. J1 pins are probably better off being straight, but they'll be clear of both Rapidus and VBXE boards (if I can figure out how to get both Rapidus and VBXE boards on the same 1200XL). Also, I had to make it a 2 layer board to get R1 tied in, so now I feel all advanced. 2 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted June 18, 2016 Share Posted June 18, 2016 So do the wider holes of U1 house a counter-sunk precision socket whose legs push straight into the motherboard socket (like the VBXE adapter)? Quote Link to comment Share on other sites More sharing options...
HiassofT Posted June 18, 2016 Share Posted June 18, 2016 U2 is a 74HC08I'd strongly suggest using a 74LS08 or a 74HCT08. The 74HC series is designed for CMOS input levels but Atari 8bit uses TTL levels. so long, Hias Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted June 18, 2016 Author Share Posted June 18, 2016 So do the wider holes of U1 house a counter-sunk precision socket whose legs push straight into the motherboard socket (like the VBXE adapter)? Kind of? I don't have a good vocabulary for part names, but I got the idea from the way mytekcontrols designed his TransKey-II, using pins and a spacer like at http://www.electronicsurplus.com/augat-740-ag14d-ic-socket-40-pin-break-away. But yes, pins that push straight into the motherboard socket U17. Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted June 18, 2016 Author Share Posted June 18, 2016 I'd strongly suggest using a 74LS08 or a 74HCT08. The 74HC series is designed for CMOS input levels but Atari 8bit uses TTL levels. Sure! I'm all for using whatever works better. The 74HC08 idea comes straight from Bob's PBI for 1200XL instructions at http://www.retrobits.net/atari/pbi.shtml. Are these the latest instructions? I guess that's one advantage of the adapter board, it'll allow easy swapping of chips to see which works better. I sent my latest design to OSH Park yesterday. $5.45 for three boards! Last time it took maybe two weeks from ordering to receiving. Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted July 3, 2016 Author Share Posted July 3, 2016 (edited) I got the boards three days ago, and they sure are pretty! Here's the bare board, and an assembled board together: Here's plugged in, but not fully booked up, to a 1200XL: It fits better than I expected, with plenty of clearance using right angle headers for J1 instead of straight. I'm a little worried about the clearance of the 74HC08 with how tight everything can be with a full load of upgrades (U1MB, VBXE, Rapidus and Simple Stereo, maybe a TK-II) but that's a problem for another day. I haven't actually tried hooking up anything that needs an ExtSel line. I'm experimenting with trying to get the Rapdius and VBXE properly working on any system before I try it on the 1200XL. So... the Slightly Easier eXtsel board has an acronym that belies what it's really worth. How about Slightly Easier Extsel (SEE)? Edited July 3, 2016 by Smokeless Joe 1 Quote Link to comment Share on other sites More sharing options...
flashjazzcat Posted July 3, 2016 Share Posted July 3, 2016 Well, it's better than "SEX". Urgh... that came out wrong. Anyway - looks excellent. 1 Quote Link to comment Share on other sites More sharing options...
Defender II Posted July 9, 2016 Share Posted July 9, 2016 I'd be interested in two. Can you post pictures of the pins on the bottom of the SEE board? How much did all the parts cost for one? Quote Link to comment Share on other sites More sharing options...
Smokeless Joe Posted July 9, 2016 Author Share Posted July 9, 2016 I'd be interested in two. Can you post pictures of the pins on the bottom of the SEE board? How much did all the parts cost for one? Full disclosure: I haven't actually tested these things. I've had a run of bad luck lately (insert sad music here) so I'm kinda taking break from breaking my Ataris. But I'm glad there's even mild interest. The board is sort of an answer to a question nobody asked, but it's a fun little project. How's this? There's no chips plugged in, but you can see the pins. The long ones are from U1, where you'd plug the original 74LS08 and where the whole thing plugs into U17. I can take a picture at another angle, if you like: You can order the bare boards here: https://oshpark.com/shared_projects/SzxNtNr2 OSH Park requires minimum orders of 3, but 3 SEEs only cost $5.45. It takes about two weeks for me to receive orders from them, and I live in Madison, WI. For the other parts, I used: Jameco 45225 (74HC08): $0.35 each Jameco 175920 (SIPP pins - gotta break these off individually): $1.75 each Jameco 37197 (14 pin socket): $0.65 each Jameco 103271 (right angle headers): $1.05 each I've got a bunch of 2.7K resistors lying around, but if I needed them, I'd order Jameco 690961: 10 for $0.099. 3 Quote Link to comment Share on other sites More sharing options...
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