As of yet, there's no PCB version of F-Ramune, but here are some instructions for building it on stripboard or breadboard!
The bill of materials is as following:
| Part | Description | Number required |
|---|---|---|
| Arduino Nano | 1 | |
| ZIF Socket with DIP-28 footprint | To fit SMD parts a SOIC-28 ZIF socket. To also be compatible with DIP chips, a DIP-28 ZIF socket can be used as the bottom layer in a… socket cake. | 1 |
| 74HC595 | 8-bit SIPO shift register | 2 |
| IRL520N | N-channel MOSFET | 1 |
| Green LED | 1 | |
| Red LED | 1 | |
| Pushbutton | 1 | |
| 10 kΩ resistor | 1 | |
| 100 Ω resistor | 1 | |
| 330 Ω resistor | 2 |
The schematic specifies the transistor to be an IRL520N, but any N-channel MOSFET with an ID (drain current) of 200 mA or higher, a VGS (gate threshold) of 4.5 V or lower and an RDS(ON) (on-resistance) of 1 Ω or lower works. The VGS requirement is for ~5 V logic signals to work. The RDS(ON) of 1 Ω is calculated based on an assumed max supply current for the memory chip of 200 mA and a max allowable voltage drop of 0.2 V (0.2 A / 0.2 V = 1 Ω). Using a more realistic max supply current of 140 mA and/or a more forgiving voltage drop limit, you can arrive at a higher max RDS(ON), and it'll probably still work fine – albeit with less leeway. If you've got MOSFETs lying around, check out their datasheets and see if they're reasonably close to the requirements!
There's no layout diagram for building F-Ramune on stripboard (since apparently there's no good digital stripboard design program!?), but it's a very reliable and permanent way to build it, so why not give it a shot? Using the schematic, you can put together something most respectable. Here's my finished stripboard:
Don't make the mistake I did and leave too little space for the socket – preferably, solder in whatever socket you're using before any wires. Measure twice, cut once, y'know?
I wouldn't recommend breadboarding F-Ramune – breadboards are unreliable, and the device uses high-speed signals and has to be quite picky with voltages. If you would like to try, though, the breadboard schematic and layout can be found in breadboard.fzz, which is a Fritzing file. Either install Fritzing and open that file, or take a gander at the image versions of the schematic and the layout diagram. The layout is somewhat optimistically routed, so some spur-of-the-moment re-routings may need to be done as space gets tight. Here's the finished product:
- Use a high-quality breadboard! Although FRAM chips consume next to no current, SRAM chips can consume up to 140 mA. Channeling that much via a breadboard with poor connections and bizarrely resistive power rails is a fool's errand – I learned this the hard way.
- If you're using a breadboard of lesser quality, keep the following in mind:
- When you insert a wire or a pin, make sure it feels like it's being gripped (and before you insert an IC, check those holes with a wire first). If it doesn't, that hole may be intermittent or flat-out broken. You can remedy this by using a different hole on the same row, replacing the strip on that particular row, or jamming a resistor leg into it.
- You may need to run wires directly to the memory chip's V+ and ground pins from the holes right by the Arduino, since going via the power rails might prove too high-resistance. Adding more bridge wires (like the ones on the far right in the breadboard diagram) may also help, albeit not as much.
- The pins on a TO-220 package such as the MOSFET here are highly destructive to breadboard holes. Use a gripping implement to turn the thin part of the pins 45–90° before inserting it, so the pins don't get gripped lengthwise and bend the breadboard's connectors out of shape.