- Intro
- Concept
- PCB
- Build firmware
- Cartrigde utility
- Total cartridge cost (32MB version)
- Photos version 2
- BOM list for version 3
- Photos version 3
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 be built at home.
Hardware and firmware initially are forked from Konrad Beckmann PicoCart64
N64 cartridge connector footprint for Eagle CAD from SummerCart64
N64 ROM boot code derived from N64FlashcartMenu and N64 DreamOS ROM
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). Unfortunately, this method has a problem with long switching of 16MB pages, because need to disable the XIP mode, enable the SPI mode to change the page and enable the XIP back. Therefore, it was decided to use QSPI with 32-bit addressing mode without XIP. To effectively work with cartridge flash chip, a special version of the filesystem was created - romfs, which allows to map sectors of saved files as a continuous data area, to which the N64 has access via the PI bus. At the moment, romfs does not support directories. The maximum memory size depends on the cartridge board version - 64 MB for version 2 with a soic-8/wson-8 8x6 flash chip package, 128 MB for version 3 with a soic-16 flash chip package.
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One user controllable LED, accessible from N64 side, RGB WS2812 for PCB version 3 (all except PicoCart64-lite)
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UART port, accessible from N64 side (all except PicoCart64-lite)
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USB passthrough to N64 side
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Emulation for EEPROM 4/16Kbit
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Emulation for SRAM 256Kbit/1MBit
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USB utility to access to the cartridge flash chip as filesystem.
| Register | Address | Mode |
|---|---|---|
| UART_CTRL | 0x1fd01000 | R- |
| UART_RXTX | 0x1fd01004 | RW |
| LED_CTRL | 0x1fd01008 | -W |
| SYS_CTRL | 0x1fd0100c | RW |
| SSI_SR | 0x1fd01010 | RW |
| SSI_DR0 | 0x1fd01014 | RW |
| FW_SIZE | 0x1fd01018 | R- |
| Function | Bit mask | Mode |
|---|---|---|
| UART_RX_AVAIL | 0x01 | R- |
| UART_TX_FREE | 0x02 | R- |
| Function | Bit mask | Mode |
|---|---|---|
| DATA | 0xFF | RW |
| Function | Bit mask | Mode | Note |
|---|---|---|---|
| LED_ONOFF | 0x01 | -W | PCB v2 or PCB v3 without WS2812 |
| LED_RGB | 0x00ffffff | -W | PCB v3 only |
| Function | Bit mask | Mode |
|---|---|---|
| EEPROM_16KBIT | 0x1000 | RW |
| SRAM_UNLOCK | 0x100 | RW |
| FLASH_MODE_QUAD | 0x10 | RW |
| FLASH_CS_HIGH | 0x01 | RW |
| Function | Bit mask | Mode |
|---|---|---|
| SSI_SR_TFNF_BITS | 0x01 | R- |
| SSI_SR_RFNE_BITS | 0x02 | R- |
| Function | Bit mask | Mode |
|---|---|---|
| DATA | 0xff | RW |
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.
After soldering, if you have 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.
Do not solder Q1 if D2 is soldered. Use either D2 or Q1.
Do not solder R1 and R6.
Do not solder R1 and D2 if LED3 is soldered.
To build, you will need an installed Pico SDK.
By default, the firmware is compiled for cartridge version 3 and NTSC. Add to cmake -DBOARD=v2 to build it for version 2 (flash chip 32/64 MB). Add to cmake -DBOARD=pico to build it for generic pico cartridge (flash chip 16 MB or less) without SI_DAT, SI_CLK, NMI, INT lines.
Add to cmake -DBOARD=pico-lite to build it for PicoCart64-lite cartridge (flash chip 16 MB or less) with SI_DAT, SI_CLK, NMI, INT lines.
Add to cmake -DREGION=pal to build it for PAL.
Steps to build:
cd fw
mkdir build
cd build
cmake ..
make -j
Press the cartridge button, connect the cartridge to USB and upload 'n64cart.uf2' to the RPI-RP2 disk.
To build, you will need an installed N64 toolchain with libdragon, compiled in opengl branch.
Add to make BOARD=pico to build it for generic pico (flash chip 16 MB and less). Add to make BOARD=pico-lite to build it for PicoCart64-lite (flash chip 16 MB and less).
Steps to build:
cd ../../rom
make
The utility is used to format cartridge memory, write and read files from cartridge memory. You can upload new roms, change the background pictures with utility.
To build for linux and Mac OS, you need to install the libusb development files.
cd ../utils
make
For windows, install mingw toolchain.
cd ../utils
make SYSTEM=Windows
The first time you use a cartridge, you must format it and write a file manager:
./usb-romfs format
./usb-romfs push ../rom/n64cart-manager.z64
Upload some other roms, for example:
./usb-romfs push rodfsdemo.z64
Change background image:
./usb-romfs push picture.jpg background.jpg
Full list of the utility commands:
./usb-romfs help
./usb-romfs bootloader
./usb-romfs reboot
./usb-romfs format
./usb-romfs list
./usb-romfs delete <remote filename>
./usb-romfs push [--fix-rom][--fix-pi-bus-speed[=12..FF]] <local filename>[ <remote filename>]
./usb-romfs pull <remote filename>[ <local filename>]
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.
| Part | Value | Device | Package |
|---|---|---|---|
| C1 | 100n | C-EUC0402 | C0402 |
| C2 | 100n | C-EUC0402 | C0402 |
| C3 | 100n | C-EUC0402 | C0402 |
| C4 | 100n | C-EUC0603 | C0603 |
| C5 | 100n | C-EUC0402 | C0402 |
| C6 | 100n | C-EUC0402 | C0402 |
| C7 | 100n | C-EUC0603 | C0603 |
| C8 | 100n | C-EUC0402 | C0402 |
| C9 | 100n | C-EUC0402 | C0402 |
| C10 | 1uF | C-EUC0402 | C0402 |
| C11 | 100n | C-EUC0402 | C0402 |
| C12 | 100n | C-EUC0402 | C0402 |
| C13 | 1uF | C-EUC0402 | C0402 |
| C14 | 100n | C-EUC0402 | C0402 |
| C15 | 27pF | C-EUC0402 | C0402 |
| C16 | 27pF | C-EUC0402 | C0402 |
| C22 | 10u | C-EUC0805 | C0805 |
| D1 | SL02-GS08 | SL02-GS08 | SOD-123 |
| D2 | GREEN | LED0603 | 0603 |
| D3 | RED | LED0603 | 0603 |
| IC1 | RP2040-QFN56 | RP2040-QFN56 | QFN-56 |
| LED3 | XL-5050RGBC-WS2812B | XL-5050RGBC-WS2812B | XL5050RGBCWS2812B |
| Q1 | BSS84 | BSS84 | SOT23 |
| R1 | 1K | R-EU_R0603 | R0603 |
| R2 | 1K | R-EU_R0402 | R0402 |
| R3 | 1K | R-EU_R0402 | R0402 |
| R4 | 27 | R-EU_R0402 | R0402 |
| R5 | 27 | R-EU_R0402 | R0402 |
| R12 | 1K | R-EU_R0603 | R0603 |
| S1 | 10-XX | B3F-10XX | |
| U$1 | LDI1117-3.3U | LDI1117-3.3U | LDI1117-3.3U |
| U2 | USB | USB-MICRO-SMD | |
| U4 | MX66L1G45GMI-08G | MX66L1G45GMI-08G | SOP_16 |
| XTAL1 | ABLS-12.000MHZ-B4-T | ABLS-12.000MHZ-B4-T | XTAL_ABLS_ABR |
