Nova64/CARTRIDGE_PINOUT.md

Nova64 Cartridge Pinout Overview

This document provides a compact, high-level technical view of the Nova64 cartridge connector from the cartridge developer perspective.

Purpose

A concise 32-pin cartridge interface for expansion modules, storage, I/O, and optional power delivery.

Connector Goals

• single edge connector for compact form factor
• separate power, data, and control signals
• support for smart cartridges and passive media
• keep SDMMC always available for cartridge-level storage access
• leave space for future expansion without extra pins
• describe pin numbering and signal roles from the cartridge edge view

32-Pin Layout

Pin	Signal	Role	Default idle state
1	GND	ground	grounded
2	VCC_3V3	supply	N/A
3	CARTRIDGE_DET	cartridge presence detect	pull-up
4	USB_FLAG	USB-capable flag	pull-up
5	USB_DP	USB D+	pull-down
6	USB_DM	USB D-	pull-down
7
8
9	SD_CMD	SDMMC command / host->cartridge control	pull-up
10	SD_CLK	SDMMC clock / host->cartridge	pull-down
11	SD_D0	SDMMC data0 (bi-directional)	pull-up
12	SD_D1	SDMMC data1 (bi-directional)	pull-up
13	SD_D2	SDMMC data2 (bi-directional)	pull-up
14	SD_D3	SDMMC data3 (bi-directional)	pull-up
15	I2C_SCL	I2C clock	pull-up
16	I2C_SDA	I2C data	pull-up
17
18	I2S_WS	I2S word select	pull-down
19	I2S_SD	I2S data out	pull-down
20	I2S_SCK	I2S clock	pull-down
21	I2S_MCLK	I2S master clock
22	SPI_MOSI	SPI MOSI (host->cartridge)	pull-down
23	SPI_MISO	SPI MISO (cartridge->host)	pull-down
24	SPI_SCLK	SPI clock (host->cartridge)	pull-down
25	SPI_CS0	SPI chip select (host->cartridge)	pull-down
26	CAN_H	CAN high	recessive bias
27	CAN_L	CAN low	recessive bias
28	UART_RX	UART RX (host->cartridge)	pull-up
29	UART_TX	UART TX (cartridge->host)	pull-up
30	VCC_5V	supply	N/A
31	GND	ground	grounded
30	EXT_5V	external power supply (optional)	N/A

Signal Groups

• Ground: pins 1, 31
• 3.3V supply: pin 2
• Cartridge detection: pin 3
• USB detection: pin 4
• USB: pins 5-6
• SDMMC: pins 9-14
• I2C: pins 15-16
• I2S audio: pins 17-21
• SPI: pins 22-25
• CAN: pins 26-27
• UART: pins 28-29
• 5V supply: pin 30
• Optional external 5V supply: pin 30

Design Rationale

• Keep storage and interface signals separate from power.
• Reserve the SDMMC channel so cartridges can provide their own software/data layer.
• Include USB and serial buses for smart module support.
• Use a dedicated ID input for simple cartridge recognition.
• Provide optional audio and GPIO for versatile cartridge types.

Notes

• This is a high-level connector map, not a full electrical specification.
• Exact pin assignments may be refined later during hardware design.
• Preferred placement for pull-ups / pull-downs is the main device, with cartridge-side resistors only used for optional or cartridge-specific functions.
• Cartridge presence should be detected via a dedicated CARTRIDGE_DET pin, not by ORing multiple ID signals.
• Cartridge features such as SD/storage, I2C, SPI, CAN, UART and audio should be discovered dynamically at runtime after insertion.
• For bidirectional power delivery, the system should use a dedicated power-path controller and a clear source priority scheme.
  • Monitor main device and cartridge voltage presence before enabling any power path.
  • If the main device is powered and the cartridge is not actively supplying power, keep cartridge supply disabled.
  • If the main device is unpowered and a powered cartridge is inserted, allow the cartridge to supply the system after voltage stability is confirmed.
  • Prevent backfeed by using ideal diodes or bidirectional power-path ICs that only conduct from the active source.

Suggested cartridge categories:

Category	Meaning
software only	cartridge provides software/application data only
special hardware	cartridge includes additional hardware functions
dynamic detection	actual capabilities are determined at runtime after insertion

USB_FLAG = 1 indicates the cartridge can present USB functionality in addition to its category.

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A short technical reference for the Nova64 cartridge connector, intended for initial design discussion.