Existing N64 flash cartridges are quite expensive, but thanks to Konrad Beckmann, who first used a raspberry pi pico as a memory controller, he managed to create a cheap version that can build at home.
Hardware and firmware initially is forked from Konrad Beckmann PicoCart64
N64 cartridge connector footprint for Eagle CAD from SummerCart64
The main idea is to make the cartridge as simple and cheap as possible. Contrary to Konrad's idea of multiplexed PSRAM chips and two RP2040, I decided to use one SPI flash memory chip and one RP2040. Modern flash chips allow to erase and flash data more than 100,000 times, which is more than enough for home use for many years. Since the RP2040 does not support SPI flash chips larger than 16MB, it was decided to use page mode with page switching through the Extended Address register (EA register).
Cartridge schematic
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The PCB and firmware supports 16, 32 and 64 MB SPI flash chips
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One user controllable LED (accessible from N64 side)
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UART port (accessible from N64 side)
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USB utility to flash roms and change the background image
Registers:
| Register | Address | Mode |
|---|---|---|
| UART_CTRL | 0x1fd01000 | R- |
| UART_RXTX | 0x1fd01004 | RW |
| LED_CTRL | 0x1fd01008 | -W |
| ROM_PAGE_CTRL | 0x1fd0100c | RW |
| PICTURE_ROM | 0x1fd80000 | R- |
UART_CTRL bits:
| Function | Bit mask | Mode |
|---|---|---|
| UART_RX_AVAIL | 0x01 | R- |
| UART_TX_FREE | 0x02 | R- |
UART_RXTX bits:
| Function | Bit mask | Mode |
|---|---|---|
| DATA | 0xFF | RW |
LED control bits:
| Function | Bit mask | Mode |
|---|---|---|
| LED_ONOFF | 0x01 | -W |
ROM page control:
| Function | Bit mask | Mode |
|---|---|---|
| TOTAL_PAGES | 0xFFFF0000 | R- |
| CURRENT_PAGE | 0xFFFF | -W |
Picture ROM size is 64KB
The thickness of the PCB is 1.2 mm.
Ordering a stencil will make it easier to apply solder paste, but will increase the cost of the order.
Do not solder Q1 if D2 is soldered. Use either D2 or Q1.
Do not solder R1 and R6.
After soldering, if you used a flux when soldering a processor or a flash chip, wash it well from the board, otherwise unstable work with memory is possible or it will not work at all.
To build, you will need an installed N64 toolchain with libdragon
Steps to build:
cd test-rom
make rom.h
cd ../fw
mkdir build
cd build
cmake ..
make
Upload firmware to the cartridge.
You can upload new roms, change the background picture with utility.
To build for linux and macOS, you need to install the libusb development files.
cd utils
make
For windows, install mingw toolchain.
cd utils
make SYSTEM=Windows
Use the utility with the console turned off, otherwise you will still have to turn it off and on.
Get cartridge info
./usb-uploader info
Write ROM file to cartrigde in ROM page 0
./usb-uploader rom 0 dfsdemo.z64
Change background image
./usb-uploader picture mybg.jpg
The price of components for an online order of one or two pieces may be lower than the cost of delivery. When ordering in several pieces, sometimes there may even be free shipping.
| Seller | Delivery cost | Components |
|---|---|---|
| Chicago Electronic Distributors | $6-$11 | RP2040 |
| Arrow | Free for orders > $50 | spi flash,resistors,capacitors,etc |
| jlpcb | $22.4 | PCB |
The price for 5 PCB is $2 ($4 for non first in order position).
The most expensive components:
| Component | qty | Price |
|---|---|---|
| RP2040 | 1 | $1 |
| W25Q256JVEIQ | 1 | $4.24 |
| ABLS-12.000MHZ-B4-T | 1 | $0.26 |
| UJ2-MIBH-G-SMT-TR | 1 | $0.45 |
| LDI1117-3.3U | 1 | $0.34 |
| BAT60AE6327HTSA1 | 2 | $0.93 |
All other components (LEDs, resistors, capacitors) from home stock, total cost less than $1.
So, the total cost of the pcb and components is approximately $9.
