DS Linker Writer/N-Card (Slot-2 USB cart)

The DS Linker Writer (also known as the N-Card, ExpressCard, DS Fire Link, etc.) is a Slot-2 GBA cartridge with an USB controller; in combination with a software USB stack running on the DS itself, it allows the console to act as an USB device.

Two variants exist:

the “D12”, featuring USB 1.1 support, based on a PDIUSBD12 chip.
- This chip was only used in early batches of the card.
- Due to a regression bug, this variant only works with older releases of uDisk. It also doesn't support homebrew built with the open source Keil stack.
the “D14”, featuring USB 2.0 support, based on an ISP1581 (or equivalent) chip.
- The most common variant.

To identify the variant in your possesion, you can use nrio-usb-disk (linked below), which displays the detected chip ID:

1012 - “D12” board (PDIUSBD12-based)
1581 - “D14” board (ISP1581-based)
other values - unknown chip
- The TinyUSB stack used by nrio-usb-disk can support 1582 and 1583 boards (ISP1582/83-based), if any such turn out to exist.
0000, FFFF - unknown board (or no board!)

Alternatively, you can compare the PCB with photos available below.

Software

NitrousTracker - music tracker, supports USB MIDI in versions 0.4.11+
nrio-usb-disk - USB mass storage driver, compatible with any Slot-1 DLDI flashcart
DSMouse - mouse emulator
DSPad - gamepad emulator
DSPad Tilt - gamepad emulator with motion controls (DSMotion/MK6/R6 required in Slot-1)
uDisk - official USB mass storage driver, supports N-Card only

Implementations

TinyUSB port - MIT licensed
- Requires a recent version of BlocksDS; comes with examples.
- Full support for “D14” and “D12” boards.
Keil USB stack port by the N-Card/DS Linker team
- Contains examples intended for an ancient version of devkitARM/libnds.
- Full support for “D14” boards.
- No support for “D12” boards.

Photos

Cartridges

These cartridges are compatible with the N-Card/DS Linker Writer. Note that the casing color differs between batches.

(Source: ApacheThunder, Disturbo)

PCB (DS Fire Link, D14)

(Source: SylverReZ)

PCB (ExpressCard Writer, D14)

(Source: SylverReZ)

PCB (N-Card, D14)

(Source: Disturbo)

PCB (DS Fire Link, D12)

Wiring

D14 (ISP1581)

The DS Linker Writer uses an ISP1581 (or clone, depending on batch) USB controller and a 12 MHz crystal.

In theory, it should be possible to replace the chip with an ISP1582 or ISP1583 in newer designs while maintaining compatibility.

TODO: Mark power pin connections?

                                  _____
                                 /     \
                           DGND / 1  64 \ VCC(3.3)
                      VCC(5.0) / 2 _  63 \ TEST
                         AGND / 3 / \  62 \ WAKEUP
                   VCCA(3.3) / 4  \_/   61 \ DGND
               USB D- <> D- / 5          60 \ XTAL1 <- 12 MHz oscillator
              USB D+ <> D+ / 6            59 \ XTAL2 -> 12 MHz oscillator
                      RPU / 7              58 \ VCC(3.3)
                    RREF / 8                57 \ DATA15 <> GBA AD15
                  MODE1 / 9                  56 \ DATA14 <> GBA AD14
                /RESET / 10                   55 \ DATA13 <> GBA AD13
                  EOT / 11                     54 \ DATA12 <> GBA AD12
                DREQ / 12                       53 \ DATA11 <> GBA AD11
               DACK / 13                         52 \ DATA10 <> GBA AD10
              DIOR / 14                           51 \ DATA9 <> GBA AD9
             DIOW / 15                             50 \ DATA8 <> GBA AD8
           INTRQ / 16                               49 \ DATA7 <> GBA AD7
                /                                       \
                \          Philips/NXP ISP1581          /
            /CS1 \ 17                               48 / DATA6 <> GBA AD6
             /CS0 \ 18                             47 / DATA5 <> GBA AD5
               DA0 \ 19                           46 / DATA4 <> GBA AD4
                DA1 \ 20                         45 / DATA3 <> GBA AD3
                 DA2 \ 21                       44 / DATA2 <> GBA AD2
                READY \ 22                     43 / VCC(3.3)
                  DGND \ 23                   42 / DGND
               VCC(3.3) \ 24                 41 / DATA1 <> GBA AD1
           GBA /CS <-/CS \ 25               40 / DATA0 <> GBA AD0
           GBA /RD <- /RD \ 26             39 / AD7 <- GBA A23
            GBA /WR <- /WR \ 27           38 / AD6 <- GBA A22
           GBA /IREQ <- INT \ 28         37 / VCC(3.3)
                          A0 \ 29       36 / DGND
               GBA A16 -> AD0 \ 30     35 / AD5 <- GBA A21
                GBA A17 -> AD1 \ 31   34 / AD4 <- GBA A20
                 GBA A18 -> AD2 \ 32 33 / AD3 <- GBA A19
                                 \     /   
                                  \   /
                                   \ /      
                                    V
                                    
                            GBA cartridge port
                            
                    |________________________________|
                    |:                              :|
                    |::::::::::::::::::::::::::::::::|
                  1 |::::::::::::::::::::::::::::::::| 32 
                     |||||||||||||||||||||||||||||||'- /GND
                     ||||||||||||||||||||||||||||||'- /IREQ           
                     |||||||||||||||||||||||||||||'- /CS2
                     |||||||||||||||||||||'+++++++- A16-23
                     |||||||||||||||||||||
                     |||||'+++++++++++++++- AD0-15
                     ||||'- /CS
                     |||'- /RD
                     ||'- /WR
                     |'- PHI
                     '- VDD

D12 (PDIUSBD12) variant

A much rarer, alternate design uses a PDIUSBD12 chip instead, configured with a separate address/data bus.

In theory, it should be possible to replace the chip with an FT120, a modern replacement chip, while maintaining compatibility. However, minor differences exist, and this has not been tested on actual hardware.