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Another IIci ROM hack

In other news, all the parts I need for the SIMM programmer (apart from the PCBs themselves) are here other than SIMM sockets--olePigeon and I are working together on that soon. Woohoo! So now I play the waiting game to see if the PCBs pass the manufacturing test with Seeed Studio.

In the process of building a couple more ROM SIMMs tonight, I accidentally lifted a pad on one of the PCBs :( I had accidentally messed up one of the PLCC sockets so I had to remove it. I tried Chip-Quik and it worked great, but I think I pulled up with too much force (and perhaps had my iron set too hot) and the pad came right off...ughh. I'm now an official member of the pad lifter club.

 
LOL! I joined it over twenty years ago, welcome aboard. Just try to avoid the brotherhood of the magic smoke on your quest, DQ! [ ;)

bbraun, that sounds like you're still making tremendous progress, nice work. :approve:

 
LOL...I'm definitely taking all precautions necessary to avoid joining the magic smoke club :)

Here's an interesting tale. One of the SIMMs I assembled last night didn't work. I found a short, but it wasn't between two nearby pads or a pad and a via or anything like that. I searched over and over and over and couldn't find anything that looked bad. However, I could tell it had to be between a PLCC pad and a trace nearby it, because it was between two lines that are next to each other (when one line is at a PLCC pad, the other line's trace is running next to that pad, and vice versa at multiple spots on the SIMM). So I got frustrated last night and gave up.

I came back to it today. I ran a really low current through the short and measured the voltage at various places to see where the short was. You can see the voltage keep increasing at various points (or dropping, depending on which side you start from) as the current flows through the circuit, it's kind of cool. I pinpointed where the short should be, but couldn't find anything, I'm guessing because it was a board defect under the solder mask, near the PLCC pad and impossible to see under the socket.

Anyway, since I had nothing to lose, I ran about 3 amps at a low voltage through the short and suddenly it wasn't drawing any more current. The short is gone and the SIMM works fine now :) I zapped it!

 
Anyway, since I had nothing to lose, I ran about 3 amps at a low voltage through the short and suddenly it wasn't drawing any more current. The short is gone and the SIMM works fine now :)
Click to expand...
You blew it like a fuse, I guess.

 
Haha, yep! I did blow it like a fuse. I saw online that some people have had mixed success with the approach so I gave it a shot and it worked :) I hope it blew the short enough that it won't creep back in. I guess if it's under the solder mask that probably won't happen.

That's the kind of magic smoke that I like! :-D

 
The programmer PCBs just shipped. If my last UPS shipment is typical of what to expect, they should be arriving later this week. :)

I also just placed my (final) order for 100 ROM SIMM PCBs since I only have one of the rev. 2 boards left (aside from the one I lifted the pad on). I made one final change at the request of bbraun to make it easy to add a switch that allows you to change the mapping so you get either the top 1 MB or lower 1 MB of the ROM space. 100 of them should be enough to last us for a while!

Also, page 26 :p

 
goodie! I woudlnt mind having one of those with a SIMM to mod my SE/30.

Edit: Dumb question, What is the minimum block write size of the Flash ICs your using? Just wondering because i hope the AVR has enough RAM to buffer a block write. Well i guess it doesnt matter as long as the serial data can keep up.

 
Woohoo, I'm looking forward to these things!

Also, the SE/30 is fun to have a working image with the ROM SIMM. The SE/30 is the worst for access to the SIMM slot.

 
Bump! And another page bites the dust! Bump! Bump!

I was wondering if the programmer would be able to handle something like reading the DeclROM of the Duo MiniDock (PLCC or some such) and then burning it onto a ROM compatible with the original DuoDock?

I have a sneeeeeeking suspicion that it may well work with the the little dog's bits installed, so's the Big Dog's Dock Services and the LCD would be enabled at the same time if booted in that config. We know that the NuBus ChipSet's function is independent of the Big Docks DeclROM because the slots work if it, or its power, are pulled.

Sooooo, the next step would be . . . [}:)] ]'>

 
Cool :) Well it'll take a while to write the firmware for it! Haha. I have some electrical test code written and I'm anxious to test it out.

The chips are writable a byte at a time. They have to be erased in 128-byte sectors, though, but that's not a big deal.

I haven't thought a great deal about performance, so we'll see how that goes. I'm hoping I can fit a bootloader on it to allow for firmware updates over USB. Hopefully the USB stack (I'm thinking about using LUFA) won't use up all my resources.

The AVR I'm using is the AT90USB646, with 64K of flash and 4K of RAM. I think if that ends up not being enough, I can switch to the AT90USB1286, which would have 128K of flash and 8K of RAM. I'm pretty sure I can make it all work with the smaller chip though, assuming the USB stack isn't a huge memory hog.

No idea on the DeclROM compatibility. I suppose if it doesn't fit the pinout of the chips I'm using, you could run wires from the pin header to hook it up correctly...

 
Cool, that or the low rent/fugly approach in an "emergency!" Wire wrap jumpers from a de-populated Socked SIMM's expansion Vias to a breadboard setup.

Me likes FUGLY! }:) ;) :o)

 
Looks like the PCBs will be here tomorrow. There's no "scheduled delivery date" like you would see on most packages, but it left Anchorage a couple of hours ago. Based on flight tracking websites, it appears they are probably en route to Louisville, which would indicate overnight delivery tomorrow...

Yes, I am that obsessed with knowing where the package is :p

I'm very, very anxious just to get a "blinking LED" program onto the AVR to see if my board design actually works.

 
In actuality, it went through Ontario, California rather than Louisville. I guess I saw Ontario International Airport and figured that meant Toronto...oops! ;-) Anyway, the programmer PCBs have arrived:

IMG_0577_shrunk.jpg

 
:D

I'm not bothering with the RS232 circuit yet:

IMG_0580_shrunk.jpg

It's drying now, but before I washed it, I powered it over USB and hooked it up to my AVRISP mkII programmer. It recognized the chip successfully :-) Always a good sign...

 
The board is alive, blinking the LED on and off. Unless I have any shorted/loose pins, I think I'm in business :-) I guess I haven't tested every single functionality of the device yet, but the microcontroller and clock circuitry seem to be working fine!

Even though I only ordered 50% electrical testing, it looks like they did 100% testing because all 10 boards have a mark on them. That's nice of them!

 
SIMM sockets should be there soon... but it is the holiday shipping season.

On a side note, I had no idea you could ship live chickens via the USPS.

 
Awesome! Thanks! I still have a lot of work to do before I can even do anything with the SIMMs, so it'll keep me busy for a while :)

Ok, now you have me a little worried...did you send me a live chicken along with the sockets? LOL

 
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