N64cart - N64 flash cartridge

• Intro
• Concept
  • Features
  • Memory mapping
• PCB
  • Order notes
  • Assembly notes
• Build firmware
• Cartrigde utility
  • Build
  • How to use
• Total cartridge cost (32MB version)
• Photos

Intro

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

Concept

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

Features

• The PCB and firmware supports 16, 32 and 64 MB SPI flash chips

• One user controllable LED (accessible from N64 side)

• UART port (accessible from N64 side)

• USB utility to flash roms and change the background image

Memory mapping

Registers:

UART_CTRL bits:

UART_RXTX bits:

LED control bits:

ROM page control:

Picture ROM size is 64KB

PCB

Order notes

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.

Assembly notes

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.

Build firmware

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.

Cartrigde utility

You can upload new roms, change the background picture with utility.

Build

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

How to use

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

Total cartridge cost (32MB version)

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.

The price for 5 PCB is $2 ($4 for non first in order position).

The most expensive components:

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.

Photos