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, for the NFP API.
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-X command set.
NFC management service "nfc:m"
| Command Header | Available since system-version | Name | Input | Output | Notes |
|---|---|---|---|---|---|
| 0x040100C2 | Unknown, <9.3.0-X | ??? | u32 unknownA, u32 unknownB, u32 unknownC, u32 (sizeof(*buffer) << 14 | 0x402), void * buffer | s32 result | |
| 0x04020000 | 9.3.0-X | ??? | void | s32 result, u32 unknownA[16] | Output seems to be a struct |
| 0x04030000 | 9.3.0-X | ??? | void | s32 result, u32 unknownA[41] | |
| 0x04040A40 | 9.3.0-X | SetAmiiboSettings | |||
| 0x04060000 | 9.3.0-X | ??? | void | s32 result | |
| 0x04070000 | 9.3.0-X | ??? | void | s32 result, u32 unknownA | |
| 0x04080000 | 9.3.0-X | ??? | void | s32 result, u32 unknownA | |
| 0x040C0000 | 9.3.0-X | ? | None | s32 result | Among other things, this will eventually call the savedata writing code referenced in the below savedata section. |
| 0x040D0000 | 9.3.0-X | ??? | void | s32 result | |
| 0x040E0000 | 9.3.0-X | ??? | void | s32 result, u32 unknownA, u32 unknownB | Again, amiibo applet ignores value unknownA. |
| 0x040F0000 | 9.3.0-X | ??? | void | s32 result, u32 unknownA, u32 unknownB |
This is used by the amiibo Settings applet. This service has the above commands, in addition to the command-set listed below.
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)).
Unlike the New3DS NFC-module, at least some of these commands are stubbed in the Old3DS NFC-module(only returns an error).
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"
| Command header | Available since system-version | Description |
|---|---|---|
| 0x00230000 | This writes the following command request data to I2C, without reading any response: 10 20 00 01 01. | |
| 0x00240000 | This writes the following command request data to I2C, without reading any response: 10 40 00 03 00 0F 01. |
This service has no known use.
Unlike the New3DS NFC-module, at least some of these commands are stubbed in the Old3DS NFC-module(only returns an error).
"nfc:u" and "nfc:m" command set
There are at least 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 system titles added with 9.3.0-21 which use NFC.
9.3.0-X
| Command Header | Available since system-version | Name | Input | Output | Notes |
|---|---|---|---|---|---|
| 0x00010040 | Initialize | u8 inputval | s32 result | ||
| 0x00020040 | Shutdown | u8 inputval | s32 result | ||
| 0x00030000 | StartCommunication | void | s32 result | ||
| 0x00040000 | StopCommunication | void | s32 result | ||
| 0x00050040 | StartTagScanning | u16 inval | s32 result | ||
| 0x00060000 | StopTagScanning | void | s32 result | ||
| 0x00070000 | LoadAmiiboData | ||||
| 0x00080000 | ResetTagScanState | ||||
| 0x00090002 | UpdateStoredAmiiboData | ||||
| 0x000A0000 | ??? | void | s32 result | ||
| 0x000B0000 | ??? | void | s32 result, u32 unknownA, u32 unknownB | amiibo applet ignores value unknownA. It doesn't even read it from the command buffer. | |
| 0x000C0000 | ??? | void | s32 result, u32 unknownA, u32 unknownB | amiibo applet also ignores value unknownA for this command. | |
| 0x000D0000 | GetTagState | void | s32 result, u8 outval | ||
| 0x000F0000 | CommunicationGetStatus | ||||
| 0x00100000 | ??? | void | s32 result, u32 unknownA[24] | ||
| 0x00110000 | GetTagInfo | ||||
| 0x00120000 | CommunicationGetResult | ||||
| 0x00130040 | OpenAppData | ||||
| 0x00140384 | InitializeWriteAppData | ||||
| 0x00150040 | ReadAppData | ||||
| 0x00160242 | WriteAppData | ||||
| 0x00170000 | GetAmiiboSettings | ||||
| 0x00180000 | GetAmiiboConfig | ||||
| 0x00190000 | GetAppDataInitStruct | ||||
| 0x001A0000 | None | No additional output. | |||
| 0x001B0000 | None | 0x36-byte output structure starting at cmdreply[2]. | |||
| 0x001C0040 | 9.6.0-X | u8 inputval | No additional output. | ? | |
| 0x001D0040 | 9.6.0-X | u32 inputval | No additional output. | ? | |
| 0x001E0040 | 9.6.0-X | u8 inputval | u8 outval at cmdreply[2]. | ? |
Pre-9.3.0-X
| Pre-9.3.0-X command header | Command header starting with 9.3.0-X | Available since system-version | Description |
|---|---|---|---|
| 0x00010000 | ? | 8.1.0-0_New3DS | Initialize |
| 0x00020000 | ? | 8.1.0-0_New3DS | Shutdown |
| 0x00030000 | ? | 8.1.0-0_New3DS | GetNFCState. This writes an output u8 to cmdreply[2]: 0 = not initialized, 1 = just initialized, 5 = data transfer ready, ... |
| 0x00040000 | 0x000B0000 | 8.1.0-0_New3DS | This writes an output handle to cmdreply[3]. |
| 0x00050000 | 0x000C0000 | 8.1.0-0_New3DS | This writes an output handle to cmdreply[3]. |
| 0x00060040 | ? | 8.1.0-0_New3DS | (u8 input) |
| 0x00070000 | ? | 8.1.0-0_New3DS | The user process must setup the output-buffer hdr+ptr data @ TLS+0x180 when using this. cmdreply[2] = actual output data size? |
| 0x00080100 | ? | 8.1.0-0_New3DS | (<0x10-bytes starting at cmdreq[1]>) |
| 0x00090000 | ? | 8.1.0-0_New3DS | |
| 0x000A0000 | ? | 8.1.0-0_New3DS | The user process must setup the output-buffer hdr+ptr data @ TLS+0x180 when using this. |
| 0x000B0042 | ? | 8.1.0-0_New3DS | (u32 size, ((Size<<14) | 2), inbufptr) |
| 0x000C0044 | ? | 8.1.0-0_New3DS | (u32 size, 0x20, <procid set by kernel>, ((Size<<14) | 0x402), inbufptr) |
| 0x000D0040 | ? | 8.1.0-0_New3DS | (u16 in) |
| 0x000E0000 | ? | 8.1.0-0_New3DS | |
| 0x000F00C2 | ? | 8.1.0-0_New3DS | (u32 unk0, u32 unk1, u32 unk2, ((Size<<14) | 0x802), inbufptr) |
| 0x00100040 | ? | 8.1.0-0_New3DS | (u32 in) |
| 0x00110040 | ? | 8.1.0-0_New3DS | (u32 in) |
| 0x00120040 | ? | 8.1.0-0_New3DS | (u32 in) |
| 0x00130000 | ? | 8.1.0-0_New3DS | Writes an output u32 to cmdreply[2]. |
| 0x00140000 | ? | 8.1.0-0_New3DS | This writes an output 0x30-byte struct starting at cmdreply[2]. |
| 0x00150000 | 0x00110000 | 8.1.0-0_New3DS | This writes an output 0x2C-byte struct starting at cmdreply[2]. |
| 0x00160000 | ? | 8.1.0-0_New3DS | |
| 0x00170000 | ? | 8.1.0-0_New3DS |
NFC services error codes
| Error-code | Description |
|---|---|
| 0xc8a17600 | The current NFC tag state, or other NFC state, is invalid with the NFC command which was used. |
NFC module savedata
- "/nfp_backup.dat" This contains raw data from the Amiibo NFC data pages. The filesize is 0x001fbd20-bytes. Certain service cmds will trigger writing to this savedata. This entire file is read during amiibo Settings startup, it's unknown what command(s) actually triggers that. It seems the Amiibo data here is updated each time the Amiibo NFC data is updated, and read each time the Amiibo NFC data is read. Data is written into this savedata when the Amiibo was never scanned on this system before. The data here is probably also updated when the scanned Amiibo NFC data doesn't match the data stored here.
During NFC writing, the NFC data being written can become corrupted if the Amiibo figure is moved outside of range during writing. When this happens, this nfp_backup data can be used to restore a previous version of that data prior to the last failed write.
nfp_backup.dat structure
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x20 | Header |
| 0x20 | 0x800 | Amiibo data table header |
| 0x7D20 | 0x21C | The NFC data for the first stored Amiibo is located here. This is the entire raw data from all 0x87 NFC data pages. |
Header structure
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x8 | Unknown, normally the following data? "00 00 02 00 02 00 00 00" (as little-endian u32s: 0x20000, 0x2) |
| 0x8 | 0x14 | Unknown, normally all-zero? |
| 0x1C | 0x4 | Unknown. CRC32 / checksum maybe? |
Amiibo data table header
This is an array with 0x40(?) entries, where the size of each entry is 0x20-bytes. Entry structure:
| Offset | Size | Description |
|---|---|---|
| 0x0 | 0x8 | First 8-bytes from Amiibo NFC serial-number. |
| 0x8 | 0x3 | Unknown, normally zero? |
| 0xB | 0x2 | u16 little-endian date value for when this Amiibo was initially written into this savedata, with the same format from here. |
| 0xD | 0xF | Unknown, normally zero? |
| 0x1C | 0x4 | Unknown. CRC32 / checksum maybe? |
NFC module versions
| System version | New3DS title-version | Old3DS title-version | Changes |
|---|---|---|---|
| 9.6.0-X | v4102 | v4106 | New3DS and Old3DS: the only changes regarding new commands is that new commands were added for the nfcu/nfcm command-set and new commands for an unknown cmd-handler were added. It's unknown if there's other changes. |
Errors
| Error code | Description |
|---|---|
| 0xC8A17620 | This is returned by NFC:OpenAppData when the appdata is uninitialized since NFC:InitializeWriteAppData wasn't used previously. |
| 0xC8A17628 | This is returned by NFC:GetAmiiboSettings when the amiibo wasn't setup by the amiibo Settings applet. |
| 0xC8A17638 | This is returned by NFC:OpenAppData when the input AppID doesn't match the actual Amiibo AppID. |
| 0xC8C1760C | Returned for HMAC-hash mismatch(data corruption), with HMAC-calculation input_buffer_size=0x34. |