Upgrading Duo's memory saves

True but I would have to add extra circuit to convert the display so it would do 1-9 and 10-16 rather than the default hexadecimal display, plus another binary counter to go beyond 16 pages (4 addresses) and when you pile up all those stuff, a few chips and mess of wires looks more complex than using a single chip and a few wires plus coding.

 

ah yes, I didnt realise you were going over 10 banks (0-9). How many are you intending to go up to?

And I would have assumed you would make a little PCB for it. Small pcbs for something like this cost next to nothing on OSHpark, look cleaner and save you time soldering it all up. You could mount the counter and the chip on the same PCB and even add in a mounting hole

 

The SRAM I am using is 32k which is 16x the original SRAM so it would be 16 pages or 4 extra address lines. I can tweak the code for larger SRAM up to 256k before I run out of free pins.

It will probably be 2 parts, one for the switch and LED display to be mounted on the case shell and one with the chip near SRAM. On my Duo-R, I'll probably use double sided foam tape and stick it on top near the back middle so the wires to SRAM is short.

If someone wanted to do what I did and didn't mind having 0-9 and A-F for display, 7493 and 7447 would work. The second set can be added, with cascade from first 7493 to second 7493 if needed for 64k, 128k, 256k, and 512k SRAM.


PS Atmega328p is a 16-bits processor. Would the added chip make my system a 32 bits system? or 56-bits when one consider PCE has 8 bit CPU and dual 16 bit GPU?

 

Been in contact with wilykat about an adapter for his mod and after his testing for fitting and pin alignment I made a quick solder board for this SRAM and the FRAM in the other thread. This has the correct pinout along with the 10k resistors on board so only thing needed is to wire the extra signals to the switch . On OSHPark it's 3 boards for $3.50 which isn't bad at all.

https://oshpark.com/shared_projects/VzfqFbvb

 

Also been working on improving mine. Originally I was going with the hexidecimal switch but I decided to be a show off and have it display the current page on 7 segment LED and using push buttons. I am about half done.

Bottom with the new SRAM:

Ignore the extra yellow wire, I ripped up A6 line when I replaced the faulty SRAM with a new one. Tiny pads are not meant to be reheated so many times.


The heart of the new system. I used an older PCB from a project I did about 3 years ago, I had about a dozen left and it was just fine for this project. Green, blue, purple, and white on bottom right goes to the SRAM's address. Brown, red, orange, and yellow is for the 2 buttons plus 5v to go with pullup resistor and ground for switch contact. The rest of wires on top left goes to dual 7-segment display. The color code is for other project and didn't apply to this one. The best part is this board can be used with Helder's adapter board above, just leave the 4 pullup resistor from the solder pads.

2 corners are held by hot glue to keep it secure, easy removal if needed. On Duo-R the top side on this area is virtually empty so this would be fine. On Black Duo, the original SRAM would be right under and this will also work with much shorter address wires.


Since I planned to mount the button switch and LED display on the top, I needed for a way to disconnect so I could remove the Duo-R's top completely. I have a bunch of connectors laying around that I just used.

And the switch board I am going to run through OSH Park later:




This board is expecting a typical 0.56" LED display with horizontal pinout and the push button with about 0.4" by 0.3" spacing, about the size of larger PCB mounted push button that can have snap on button top. Plus pin headers, the 6th pin of the 10 pin connector is not used and was intended to function as key with a filled in 6th hole on the connector. I only had 9 pins cable connector, I thought I had 10 so I'll need to get a female socket (Dupont style), the pins are easily transferred.

 

Still don't have the final PCB but the proto I made shows it all works:


I put Neutopia in page 1, restarted, changed to page 2, played Neutopia 2 and put a save there. Then restarted, switched back to page 1 and loaded Neutopia, it loaded fine. Next loaded bram checking program I downloaded to my turbo ED and it shows saves on both page 1 and 2.

My mod is working along with the LED display and buttons. I'm going to wait for a neater looking board from OSH Park before I cut in my case for permanent install.

I added to the first page the 3 different ways one could control address lines.

 

Epic mod well done Wilykat.

 

I'd like to do this in the turbo CD base. It should functional be the same right?

 

Should be the same, CD base uses SOIC, they should be on the middle PCB, the digital board that has the EXT connector. Taking the CD base apart is a pain in the ass though, the 2 I took apart to recap did not have convenient means of disconnecting all those wires so you will have 3 PCBs tethered and a bit of challenge in removing the original SRAM without breaking the wire or melting them.

 

I'm comfortable disassembling it and removing smd chips, though the glue is a concern, I'll attempt when you guys have a pcb for sale.

 

If you use hot air to remove the IC it should loosen the glue

 

The glue is pretty brittle.
Light lifting with a small screwdriver where there are no tracks will free the IC.

 

Hot air does indeed make light work of it. It's same deal with the saturn bios

 

Never had to use hotair and have done Saturn dreamcast Pc engine Snes chip removals.

 

No one has said you have to use hot air. But hot air is correct tool for smd rework. It is much easier with it than without.

You can also pick up those atten units for so cheap that there's no reason not to use it.

 

I do plan to get one someday, maybe this year. It does also help with small DIP IC that are otherwise difficult to remove like a bad RAM chip in C64.



Heat the whole thing and the IC comes out, then blow out the plugged holes. Sure looks easier than my usual vacuum desoldering not to mention less stress on my thumb.

Back to my Duo hack, I put an order on OSHPark for the board, a few new pushbutton switches and some more LED display. The proto board I made can still be used for anything being modular and not oddly wired or such. It may be around 2-3 weeks to get them all and finish my mod.

Now to see if I can remember where I put that Sega CD and see if the same hack can be applied.

 

No need to get upset Bad_Ad84 it was only a statement of experience. Not a dig at you
As a lot of stuff done on console is remove to replace .
Hot air reworking is not needed.

 

Not upset, your post just seemed to imply it was being said that you must use hot air to get it done.

But you can certainly cut the legs or do it many other ways, but with hot air you get to save the part, its easier and faster IMO. The glue also comes away with much less force once its been heated - also less risk of damage to the PCB etc. When you can buy a decently performing hot air station for £30, it seems silly not to have one if you do any real amount of SMD work.

 

It was a personal statement nothing more nothing less.

 

New boards came in today and I got it done



The button top are only temporary as the ones I wanted to use hasn't shown up. It looks so much neater than my proto board