NFC Services

The New3DS NFC module was added with 8.1.0-0_New3DS. The Old3DS NFC module was added with 9.3.0-X.

On New3DS NFC module uses the NFC hardware via the i2c::NFC and gpio:NFC services. On Old3DS NFC module communicates with a NFC peripheral via IR with the IRUSER service.

A total of 6 sessions can be open simultaneously for all of these services combined.

NFC services

NFC user service "nfc:u"

This is the NFC service used by regular applications.

This was first seen in the Super Smash Bros eShop demo (only in the exheader, the demo doesn't actually use it), but at that time no system-module was available for NFC on CDN. The first regular application to use this service was Super Smash Bros, with the v1.0.5 game-update, which used the new 9.3.0-21 command set.

NFC management service "nfc:m"

This is used by the amiibo Settings applet.

NFC development service "nfc:dev"

This service seems to be intended for use only on dev-units(or at least some of the command(s)).

NFC service "nfc:p"

This service is used by the mint library-applet, starting with 9.3.0-21. This service was added to the mint service-access-control list with 9.0.0-20.

NFC service "nfc:r"

This service has no known use.

NFC service "nfc:s"

This service has no known use.

"nfc:u" and "nfc:m" command set

There are two different revisions of the NFC module. First version was introduced on New3DS only with firmware 8.1.0-0_New3DS. Second version made its appearance with 9.3.0-X, on both Old3DS and New3DS.

These two versions are not interchangeable and not compatible, since the newer version uses a different command set and has no implemented commands from the older version. This does not introduce compatibility problems since no retail software used the NFC module before the Super Smash Bros for 3DS, whose NFC update required 9.3.0-21.

Post-9.3.0-21

Commands for post-9.3.0-21 have been extracted by analyzing the amiibo Settings applet. Therefore this table may be missing commands.

Command Header	Command	Description
0x00010040	nfcInit(void)	Initializes the NFC service.
0x00020040	nfcStop(void)	Deinitializes the NFC service.
0x04060000	???(void)	???

Pre-9.3.0-21

Command Header	Description
0x00010000	Initialize
0x00020000	Shutdown
0x00030000	GetNFCState. This writes an output u8 to cmdreply[2]: 0 = not initialized, 1 = just initialized, 5 = data transfer ready, ...
0x00040000	This writes an output handle to cmdreply[3].
0x00050000	This writes an output handle to cmdreply[3].
0x00060040	(u8 input)
0x00070000	The user process must setup the output-buffer hdr+ptr data @ TLS+0x180 when using this. cmdreply[2] = actual output data size?
0x00080100	(<0x10-bytes starting at cmdreq[1]>)
0x00090000
0x000A0000	The user process must setup the output-buffer hdr+ptr data @ TLS+0x180 when using this.
0x000B0042	(u32 size, ((Size<<14) | 2), inbufptr)
0x000C0044	(u32 size, 0x20, <procid set by kernel>, ((Size<<14) | 0x402), inbufptr)
0x000D0040	(u16 in)
0x000E0000
0x000F00C2	(u32 unk0, u32 unk1, u32 unk2, ((Size<<14) | 0x802), inbufptr)
0x00100040	(u32 in)
0x00110040	(u32 in)
0x00120040	(u32 in)
0x00130000	Writes an output u32 to cmdreply[2].
0x00140000	This writes an output 0x30-byte struct starting at cmdreply[2].
0x00150000	This writes an output 0x2C-byte struct starting at cmdreply[2].
0x00160000
0x00170000

NFC module savedata

• "/nfp_backup.dat" Going by the filename this seems to contain data backed up from amiibo.