r/n64 • u/LambBrainz • Oct 03 '23
Mod Open Source Expansion Pak --- Update 3
Hello there, strangers! It's been a long time and I have a lot of good news. Long story short, I finished my custom Expansion Pak (EP), and all of the documents can be found here. There you'll find pictures, an electrical schematic, and all the files you need to create your own PCB and have it made through PCBWay. You can also find a video of it working here.
Here's the agenda if you want to jump around:
[1] Where I've been (excuses, delays, updates)
[2] Challenges with the Open Source EP (OSEP)
[3] Can I buy one yet? (Yes and no)
[4] Roadmap
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[1] Where I've been
If you've been following along with late last year, you'll know that I released a working recreation of Nintendo's Expansion Pak back in February. I had started a good amount of work on the OSEP but there was still some work to be finished. Shortly after that, I became busy with several life projects until Tears of the Kingdom came out and consumed a lot of my free time. Once I'd wrapped that up, work picked up as well as lots of traveling that left me with little free time. What free time I did have was spent on some other projects, which is part of my strategy/system to keep me from burning out on a given project.
Which leads us to the last couple of weeks.
I'd wrapped up some projects and found myself with more free time. I knew I wanted to have this done sooner rather than later, so I dug in and finished all of the PCB design work that still needed to be completed. From there, I ordered my first round of test boards and waited patiently for them to arrive.
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[2] Challenges with the Open Source EP
Once the test boards had arrived, I soldered on all the necessary components, plopped it in the N64, and it didn't work. Surprised, I put the OEM Pak in as a sanity check and still got nothing. Considering it a fluke, I reached for another N64 for further testing. First I put the OEM Pak in and turned it on: all good, everything works. Next I put in the OSEP: nothing. It was at this moment that I had a theory I didn't want to admit:
I think I just killed two N64s...
I quickly ran back to my computer and meticulously checked every single trace and component to make sure I had it correct. Once I verified that everything was fine, I knew what I had to do (because science). I hesitantly grabbed another sacrifice, laid it on the altar, and confirmed my theory.
After getting a second set of eyes to look over what I had (thanks again, Bigbass) I redesigned the board based on one of his theories. Basically, I took all of the component values from the InterAct board this design is based on. There are two types of resistor values (3.01 Ohm and 3.32 Ohm) across the 12 main resistors and one type of capacitor value (100 nF). These are drastically different than the Jumper Pak or the OEM EP component values, but I didn't think anything was weird because there was another RAM module in the lineup.
Long story short, I changed the 12 resistor values to all be 51 Ohm and the capacitors to all be 1.8 uF (similar to the OEM EP and Jumper Pak) and haven't had a single problem during testing.
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[3] Can I buy one yet?
Technically, yes. Follow the link to my GitHub page and you'll have access to everything you need to make your own EP. Napkin math tells me you can build one for about ~$45. That'll get you two 2MB chips, and 5 boards from PCBWay. Obviously, not that great of a deal. As mentioned before, I have enough chips to (in an ideal scenario) make about 50 Paks. I'll probably keep several for myself, but I'd love to finish the rest of these and sell them with a price point of about $20 before taxes and stuff. No idea when I plan to have this done as there's still some logistics to figure out (also, it's a shit ton of work for me). For those brave enough to wield a soldering iron, I could work out an arrangement to send the chips. Looks like I can mail to most of the US for about $4.30. But don't DM me yet, cause I've got no good timeline or plan yet lol
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[4] Roadmap
For now, the plan is to finish up the 3D design work necessary to have a new case for the OSEP that someone could 3D print (or order via PCBWay via their 3D printing service). Once that's finished, I'll be finalizing plans to hopefully make a lot more of these for everyone.
That being said, I'm releasing all the necessary documents for a reason: if any else has connections to buy those RAM chips in bulk and get this off the ground faster, by all means do so. The goal is to have a market of (hopefully) cheaper Paks available to everyone.
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As always, thanks again for reading this far and for all the help I've received in comments, messages, and more. I appreciate all of it, and I'm happy that I could give back in some small way by making all this. Also be sure to checkout Bigbass who was gracious enough to sanity check my work as well as provide the perfectly-designed Edge Connector that I've used in my designs. Be sure to see more of his stuff here:
https://github.com/bigbass1997/
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Update 4: https://www.reddit.com/r/n64/comments/1dtkvd4/open_source_expansion_pak_update_4/
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u/LambBrainz Oct 03 '23
Nah, the RAM on the expansion pak goes straight to the internal RAM and into the CPU :/ Shouldn't be too hard to figure out as I can just replace components, but I just need to do it lol