brain

Isn't there a HexBus Adapter for the 4/A That could be copied to do this?

Someone made a "buffer" board. the 3 '244s buffer the 16 address lines and the control lines (probably R/W, E, Q, CTS, SCS, RESET, but not CART or NMI) and the 245 buffers the 8 data lines. You can then probe all the lines at the cart without risking damage to the CoCo itself. Nice option for experimentors.

PM me an address and I'll send my entire unit. You can mix and match and see what is going on. Jim

Hmm, that is odd. Just %ffs? Any chance I could see the output?

Mine is FAT32, since it's a larger card. I tried a freshly formatted FAT32 card, with good results. One thing you can try is running a terminal app and selecting the COM port of your Arduino @ 57600 bps. Reset the Arduino. You should see: Mount SD RC: 00 Device ID: 0x64 If not, then we have other issues. Jim

On the chance it's a code issue, I put my working bin and hex file at http://www.go4retro.com/downloads/HEXTIr. Try those. If they do not work, I'll just pack up my unit and mail it to you, so you can mix and match and see what is going on.

I had the HSK signal on the wrong pin. Working now. Let me look at your pinout. It looks like you have your top row of HEXbus and bottom row of hexbus switched around (and D2/D3 swapped). looking at the underneath of your board, you have (L-R) (on top row): HSK, BLANK, D3 D2 and (bottom row) D0, D1, BAV,GND. But, you have have (L-R) Top: D0, D1 BAV, GND and Bottom: HSK, BLANK, D2, D3 Try that.

OK, good news is that I get the same behavior on Arduino. Bad news is that I get the same behavior on Arduino (no workie). Debugging now.

I was looking at the specs as defined on the HexBus stuff and determining how to implement from that. Jim

The cc40 is emulated, I thought. That would give video controller data Jim

Sounds like some debugging is in order. I can put my kit together again, but it'll be a few days. If the arduino uses the USB as a serial port (I think it does), then you might be able to use the built into UART code in the prj to sniff out what is going on when the save is requested. BAV should go low, as I recall, and HSK should then almost immedaitely go low to ack the request. It sounds like that is not happening. Jim

The unit responds by default on #100 The LED does double duty. When on, it means file is open. When flashing, it means an error has occurred. The unit has code to set the device # from 100-107: static inline uint8_t device_hw_address(void) { return 100 + !((PIND & (_BV(PIN4) | _BV(PIN5) | _BV(PIN6))) >> 4); }

Yes, that is correct. Maybe add that to the pull request

OK, new Makefile pushed to repo.

Something is wrong with the autoconf.h build target... Looking at it now.

That file is created by AWK, which you dloaded and installed, so not sure. Maybe doa make clean and then try again.

Pull and create a merge request for the install docs and I will merge. I'd rather not put the binary in there, since it'll be in the obj directory, and those are specific to board. Jim

make CONFIG=config-arduino progall You'll probably need to find make and avr-gcc and friends in your environment somewhere and make sure they are in your path.

I didn't convert it to an Arduino project. You can use avrdude to program the raw AVR binary into the system.

This. So much this. I've done it twice. It's not a simplistic affair, it's prone to mistakes, and it looks terrible in the end. (But, it does work). Still, if you're doing this today, with new parts, use the separate coin cell if at all possible. Jim

Discussion are always good. It just seemed like it was turning into a SMT versus TH debate. And, I'm probably not the person to evangelize the TH option, since I do most of my current designs as SMT, for which I get lambasted by the retro "purists" who claim that retro HW should only use parts from the era. Yes, those people exist. I'm perusing the 26 page F18A MK2 thread at this late hour, so I see... It was on my list of pages to scan a few days back, but I just got to it tonight. Still, much like some of the middle pages of the F18A MK2 thread), there's been lots of posts on this thread that didn't move the ball forward (mine, for example, agreeing that the replacement parts fit the original footprint, but it's a mot point, since the original part is wrong for the design. The folks trying to justify the 3V3 coming out of the RTC as being why it's ok, when that's just another wrong path, as the IO lines will be slammed with 5V signals the SRAM can't handle. And, then this whole portion I'm probably flogging the dead horse on about a recreation and what design ethos to pick for such a task, when the OP really just wanted to know which part would work - answer: none of the ones they listed 🙂) The easy solution (for the OP, anyway) is to source the TC554001A part and have someone update the BOM on that page to remove the 3v3 part listed (as it's wrong, to your original point). Hopefully we'll hear from the OP on the matter. It probably depends on what the masses really want. I stopped by because I had expertise to check datasheets, and the OP asked. An IDE interface is a well traveled path for myself, but I don't know that I need one for my PEB right now. On the other hand, I've been struggling to find a nice way to do something of value with the TI 99/4A I own, since I use such projects to learn the platform. I didn't actually know this was for a bulk buy/build honestly, I just came for the datasheet ask 🙂 A fair progression. On the other hand, IDE is easy, it's still available (it seems like you can buy new drives, not sure if just NOS, or what), and for someone looking for a PEB design #1, it could be interesting. I do agree that a design that implements a FDD and HDD controller but talks Wifi or Ethernet out the back end is a better option, but crawl, walk, run, as they say. Well, my counterpoint to your note was that if I was recreating the design, I'd just design up the schematic + PCB, have the first spin, solder it up, test it out, make the bodge fixes, update the schematic, and respin a final board for those who wanted the design (I put all my stuff on github.com, so folks could pull from there). I wasn't suggesting recreating and then just throwing the untested design online for everyone to debug. When I do TH designs, it's just easier anymore to do up the board in EAGLE (I'd love to slide over to KiCAD, but I'm so fast on EAGLE, and learning a new schematic capture/PCB CAD tool at this point seems like a waste of time I could spend designing another idea), spin it, and test that way. breadboards always seem to fail me at the worst moment, and I rarely find the time to hand solder up a perfboard of an entire project (I can do little adapters or real simple projects, but anything reasonably complex I forget a trace and waste time tracking it down, etc.) Yes, and it's a fine point. The part referenced in the original post is, quite frankly, unworkable. And, thus, so are the possible replacements. Jim

I'm happy to be wrong, but I don't see a way to cut that much cost out of the PCB. You could arguably cut out the middle and top of the PEB card, but you need both sides to hit the guides, and you need to leave enough there (probably 1-2") to keep the strength and not allow the corners to be weak spots, you would still have plenty of room to use through hole. With a U-shaped PCB, you could panelize and use the interior as another PCB's "sides", but I'm not sure it'll be a huge savings in cost. As for assembly, it doesn't really matter to me. PCBA is $0.016 per pad, at the place I use, regardless of SMT or TH. No difference in lead time either. If I was going to spin the board, I'd put the CF connector on the outboard PCB component (not sure what you call that part), and put a 2mm 44 pin laptop IDE connector in the middle to plug in a laptop IDE drive, with an IDE 40 pin connector next to it, for a cable for the 40 pin IDE drives. That should cover all the bases. Maybe arcane is the not the best word, but the fact that we're on page 2 of a conversation about it suggests too much time has been spent on it. As I noted last night, the existing design will work fine with the alternate 5V SRAM SMT part specified in the parts list, as it's 5V. It's still hard to find, but if this just a small run, I am sure utsource or online components has it at a reasonable price. UTSource does, at ~$1-1.20: https://www.utsource.net/sch/TC554001A If I was going to go surface mount, I'd just scrap all the TTL, put in a Xilinx 9572XL or 144XL and the RAM (could do 4MB at that point, but not sure if this is a SAMS-compatible SRAM card already or not, haven't even looked at the schematic), RTC, and IDE/CF port. But, it seems like this is an ideal kit project, and TH looks very doable. Alliance makes a nice 5V DIP 512kB SRAM: (https://www.digikey.com/product-detail/en/alliance-memory-inc/AS6C4008-55PCN/1450-1027-ND/4234586) that fits this use case perfectly. Anymore, I just lay out the board in EAGLE, buy a 5 pack of prototype boards, solder up and debug the design, and then re-spin. $20 or $200, doesn't matter. I believe we should agreeably agree to disagree. I am insanely comfortable with SMT, using it in many of my products I offer for sale, but I also enjoy TH work. I can't argue the points that SMT is smaller and it's not beyond the hobbyist to solder, but I don't see the need in this case, and the SMT parts will make lots of folks shy away from doing it as a kit, even though you rightly point out that SOIC is easy for the novice solderer. I see the board as being huge no matter what one does with the design, so the value of smaller size of parts concerning board size reduction will be lost. Cost is about equal. You probably save a buck or two in parts by going SMT on the TTL, and about $2.00 using SMT RAM instead of SMT. My main issue right now is that I don't have an EAGLE lbr with the PEB card dimensions and the edge connector already. Otherwise, I probably would have skipped responding to the forum posts and just laid out the recreation, as it looks to take part of an afternoon, tops. Jim

I'll defer to the OP on that. I'm not fully invested in this, just noting some help I could offer if needed. Jim

As a designer, I'm aware of the advantages of SMT, but I don't see the necessity in this case: It's a PEB card. The design has tons of room, according to the gerbers on the site I spot checked a few of the parts. 74ALS02 is #.35 for DIP, $70 for SOIC. Granted, the cheap part is a non stock, but active, but even the normally stocked Digikey DIP part is $.84, hardly cause for pricing concern. The others look to follow the trend. All of the parts look easily available in active status at Digikey. I offered because it looks like finding this arcane SRAM is taking up a lot of mental bandwidth, PCB design is not tough (given at least a nominally working schematic), it would seem laying out a board and having a real schematic (as opposed to this ASCII stuff on the page) would greatly help in debugging, and how would one debug without a real board to test with, and if folks would appreciate a through hole design, it seems easier to just recreate the board as TH and then debug it. (TH boards are easier to pull ICs and debug than SMT, anyway. Jim

I'd possibly be willing to redo the schematic and PCB and make it all through hole, but I'd need help... If I did, I'd probably make the entire design through hole parts, since I don't know that I see any reason it all has to be surface mount.