105 lines
5.9 KiB
Markdown
105 lines
5.9 KiB
Markdown
# Nova64 Cartridge Pinout Overview
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This document provides a compact, high-level technical view of the Nova64 cartridge connector from the cartridge developer perspective.
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## Purpose
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A concise 32-pin cartridge interface for expansion modules, storage, I/O, and optional power delivery.
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## Connector Goals
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- single edge connector for compact form factor
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- separate power, data, and control signals
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- support for smart cartridges and passive media
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- keep SDMMC always available for cartridge-level storage access
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- leave space for future expansion without extra pins
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- describe pin numbering and signal roles from the cartridge edge view
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## 32-Pin Layout
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| Pin | Signal | Role | Default idle state |
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| --: | ------------- | --------------------------------------- | ------------------ |
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| 1 | GND | ground | grounded |
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| 2 | VCC_3V3 | supply | N/A |
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| 3 | CARTRIDGE_DET | cartridge presence detect | pull-up |
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| 4 | USB_FLAG | USB-capable flag | pull-up |
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| 5 | USB_DP | USB D+ | pull-down |
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| 6 | USB_DM | USB D- | pull-down |
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| 7 | | | |
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| 8 | | | |
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| 9 | SD_CMD | SDMMC command / host->cartridge control | pull-up |
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| 10 | SD_CLK | SDMMC clock / host->cartridge | pull-down |
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| 11 | SD_D0 | SDMMC data0 (bi-directional) | pull-up |
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| 12 | SD_D1 | SDMMC data1 (bi-directional) | pull-up |
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| 13 | SD_D2 | SDMMC data2 (bi-directional) | pull-up |
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| 14 | SD_D3 | SDMMC data3 (bi-directional) | pull-up |
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| 15 | I2C_SCL | I2C clock | pull-up |
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| 16 | I2C_SDA | I2C data | pull-up |
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| 17 | | | |
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| 18 | I2S_WS | I2S word select | pull-down |
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| 19 | I2S_SD | I2S data out | pull-down |
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| 20 | I2S_SCK | I2S clock | pull-down |
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| 21 | I2S_MCLK | I2S master clock | |
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| 22 | SPI_MOSI | SPI MOSI (host->cartridge) | pull-down |
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| 23 | SPI_MISO | SPI MISO (cartridge->host) | pull-down |
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| 24 | SPI_SCLK | SPI clock (host->cartridge) | pull-down |
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| 25 | SPI_CS0 | SPI chip select (host->cartridge) | pull-down |
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| 26 | CAN_H | CAN high | recessive bias |
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| 27 | CAN_L | CAN low | recessive bias |
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| 28 | UART_RX | UART RX (host->cartridge) | pull-up |
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| 29 | UART_TX | UART TX (cartridge->host) | pull-up |
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| 30 | VCC_5V | supply | N/A |
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| 31 | GND | ground | grounded |
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| 30 | EXT_5V | external power supply (optional) | N/A |
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## Signal Groups
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- Ground: pins 1, 31
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- 3.3V supply: pin 2
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- Cartridge detection: pin 3
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- USB detection: pin 4
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- USB: pins 5-6
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- SDMMC: pins 9-14
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- I2C: pins 15-16
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- I2S audio: pins 17-21
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- SPI: pins 22-25
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- CAN: pins 26-27
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- UART: pins 28-29
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- 5V supply: pin 30
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- Optional external 5V supply: pin 30
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## Design Rationale
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- Keep storage and interface signals separate from power.
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- Reserve the SDMMC channel so cartridges can provide their own software/data layer.
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- Include USB and serial buses for smart module support.
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- Use a dedicated ID input for simple cartridge recognition.
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- Provide optional audio and GPIO for versatile cartridge types.
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## Notes
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- This is a high-level connector map, not a full electrical specification.
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- Exact pin assignments may be refined later during hardware design.
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- Preferred placement for pull-ups / pull-downs is the main device, with cartridge-side resistors only used for optional or cartridge-specific functions.
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- Cartridge presence should be detected via a dedicated `CARTRIDGE_DET` pin, not by ORing multiple ID signals.
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- Cartridge features such as SD/storage, I2C, SPI, CAN, UART and audio should be discovered dynamically at runtime after insertion.
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- For bidirectional power delivery, the system should use a dedicated power-path controller and a clear source priority scheme.
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- Monitor main device and cartridge voltage presence before enabling any power path.
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- If the main device is powered and the cartridge is not actively supplying power, keep cartridge supply disabled.
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- If the main device is unpowered and a powered cartridge is inserted, allow the cartridge to supply the system after voltage stability is confirmed.
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- Prevent backfeed by using ideal diodes or bidirectional power-path ICs that only conduct from the active source.
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Suggested cartridge categories:
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| Category | Meaning |
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| ----------------: | ------------------------------------------------------------- |
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| software only | cartridge provides software/application data only |
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| special hardware | cartridge includes additional hardware functions |
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| dynamic detection | actual capabilities are determined at runtime after insertion |
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USB_FLAG = 1 indicates the cartridge can present USB functionality in addition to its category.
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---
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A short technical reference for the Nova64 cartridge connector, intended for initial design discussion.
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