Nintendo Wireless Adapter Specification

1.1 (23th June 2005) by denopqrihg ([email protected])

This document describes how a GBA program can communicate with a plugged-in Nintendo wireless adapter. This info is not 100% accurate, nor am I responsible for any damage it may do. I am only sharing my partial knowledge.

Some general info

The Nintendo Wireless Adapter is a device that presents more multiplayer features than the link cable. It uses a kind of server/client approach (broadcasting, connections etc.). It allows to send quite large amounts of data at once (most I've seen was 80 bytes), has built-in synchronisation and much more.
This document is only about two player link. At the moment, I have no info about how it works with mre players. If you don't understand something in this document or think something is unclear, contact me and I'll try to clarify.

Which mode to use?

32-bit Normal mode, all the time. No exceptions.
Mostly 2Mbit internal clock, but there are exceptions which will be pointed out.

Initialization

Use: 32-bit Normal mode, 256Khz internal clock.
Send the text "NINTENDO/0x01/0x80" in the following manner:
Store two bytes of the text in the lower 16 bits of the send data. The upper 16 bits should be 1's complement of the previously received lower 16 bits. Send it. Received data should look like the one you sent, except that the upper and lower halfword are swapped. Repeat this process until you have sent the whole string (the last two bytes are 0x8001).

Example:

Send	Receive
0xgggg494e	0x494egggg
0xb6b1494e	0x494eb6b1
0xb6b1544e	0x544eb6b1
0xabb1544e	0x544eabb1
0xabb14e45	0x4e45abb1
0xb1ba4e45	0x4e45b1ba
0xb1ba4f44	0x4f44b1ba
0xb0bb4f44	0x4f44b0bb
0xb0bb8001	0x8001b0bb

(gggg = garbage)

Then send command 0x3d or 0x10, difference is unknown (what is a command and how to use it is in the next section).

Communication

The adapter uses a form of communication that I call 'commands'.
It waits until you send a command to it, and then it does something according to what command you sent.
The format is:
0x9966wwcc
cc is the 1-byte command
ww is a number indicating how many 4-byte units of data will follow the command (I don't know what happens when you send data with a command that shouldn't send any).
When you send this, you always receive 0x80000000 (also when sending the additional data).
Then, you must send 0x80000000. You then receive a similar structure, 0x9966wwaa.
ww is again a number of words (4 byte) following this command
aa is the command you sent ORed with 0x80 (with some exceptions)
If there was a nonzero word count in the response, send 0x80000000 the apropriate number of times and store the data you receive (you requested it, so you should store it).
Remember to keep some delays between transfers.

Example:

Send	Receive
0x99660117	0x80000000
0x003c0720	0x80000000
0x80000000	0x99660097

Another example:

Send	Receive
0x9966001a	0x80000000
0x80000000	0x9966019a
0x80000000	0x00001547

Ackowledging

After each transfer (except initialization), a kind of 'acknowledge procedure' must be done (maybe it isn't necessary, but the games do it):

Right after the transfer ends, output SO=low, wait until SI becomes high, then output SO=high and wait until SI=low.
⚠️ Exception ⚠️ After commands 0xa5 and 0xa7, the polarity is 'swapped': output SO=low, wait until SI=low, then send SO=high and wait until SI=high

Also, just before each transfer, set SO=low
(This part is a bit unclear to me, maybe it doesn't work like this at all)

Commands

Many commands have completely unknown function, some of them must be sent but nobody knows why and what they mean. This is not a complete list of commands, I only listed the commands that either are important or I know something about them.

I will use the following notation:

Command: Command number
Send: how many words to send
Receive: how many words to receive
Description: what the command does (if known :-)

Command	Send	Receive	Description
0x10	0	0	Last step of initialization, difference between this and 0x3d is unknown, both are used 0x10 seems to be 'safer'
0x11	0	1	This command always receives 0xff in 2 player link, maybe it has to do with 3+ players ??
0x13	0	1	Receives a random value, don't know what it's for
0x16	usually 6	0	Sends 'broadcast' data, which will be received by all adapters in range
0x17	1	0	Setup?? The value sent should be 003d0620 (Digimon), 003c0420 (Pokemon) or something along this way.
0x1a	0	0 or 1	This command is used by the 'server' to check if someone wants to connect. If not, no data is received. If yes, you'll get a value (random? or ID?)
0x1d
0x1e	0	multiples of 7 (usually)	Read 'broadcast' data. Data from each adapter is prefixed by one word containing an 'ID' of the adapter , which is used when you want to connect.
0x1f	1	0	Connect to server. Value sent is the 'ID' of the adapter you want to connect to.
0x20	0	1	Used after 0x1f, generally resend until highest byte is 0.
0x21	0	1	Send once after 0x20 successfully finished (returned 0).
0x24	anything	0	Send data to connected adapters (I've only seen this command used by servers, but maybe clients can use it as well)
0x25	anything	0	Same as `0x24`, with the exception that this command 'waits' until incoming data is available. This keeps the games synchronized without any further in-game programming. How to use: After you send all the data and get `0x996600a5` from the adapter, store `0x80000000` in the send data register and start a transfer with `_EXTERNAL_` clock. Once the data arrives, you'll receive a `0x99660028` command (which you have to ackowledge just like the adapter - send back `0x996600a8`). Also note that after you receive the `0x996600a5` until you use the next command (usually `0x26`), the polarity of the SI and SO conmfirmation procedure is swapped.
0x26	0	anything	Receive data.
0x27	0	0	Similar to 0x25, but without sending data. All strange behavior of 0x25 applies here, too.
0x30	1?	0	Most likely a 'Terminate connection' command. Data value is usually 1.
0x3d	0	0	Same as 0x10
0xa8	0	0	Ackowledge of 0x28 sent by adapter.
0xee	1?	0	This is very unconfirmed, but is probably used when you want the adapter to resend the last command/whatever ??

Example

A complete example of a client/server communication
(all numbers are in hex)

Server

0x128 reg means the value of 0x128 reg

0x128 reg	Send	Receive
5084	00000000	garbage
5085	ffff494e	494egggg
5085	b6b1494e	494eb6b1
5085	b6b1544e	544eb6b1
5085	abb1544e	abb1544e
5085	abb14e45	4e45abb1
5085	b1ba4e45	4e45b1ba
5085	b1ba4f44	4f44b1ba
5085	b0bb4f44	4f44b0bb
5085	b0bb8001	8001b0bb
5003
5083	99660010	80000000
500b
5003
5083	80000000	99660090
500b
5003
5083	99660117	80000000
500b
5003
5083	003c0420	80000000
500b
5003
5083	80000000	99660097
500b
5003
5003
5083	99660616	80000000
500b
5003
5083	0c020002	80000000
500b
5003
5083	00005ce1	80000000
500b
5003
5083	00000000	80000000
500b
5003
5083	09000040	80000000
500b
5003
5083	c1cfc8cd	80000000
500b
5003
5083	00ffccbb	80000000
500b
5003
5083	80000000	99660096
500b
5003
5083	99660013	80000000
500b
5003
5083	80000000	99660193
500b
5003
5083	80000000	02001234 (example)
500b
5003
5083	99660019	80000000
500b
5003
5083	80000000	99660099
500b

repeat

0x128 reg	Send	Receive
5003
5083	9966001a	80000000
500b
5003
5083	80000000	9966009a
500b

until you get:

repeat a few times to ensure that it really is a connection

0x128 reg	Send	Receive
5003
5083	9966001a	80000000
500b
5003
5083	80000000	9966019a
5003
5083	80000000	00004875 (example)
500b
5003
5083	99660011	80000000
500b
5003
5083	80000000	99660191
500b
5003
5083	80000000	000000ff
500b

0x128 reg	Send	Receive
5003
5083	99660124	80000000
500b
5003
5083	12345678	80000000
500b
5003
5083	80000000	99660094
500b

repeat until you get some data

value of 0x128 reg	Send	Receive
5003
5083	99660026	80000000
500b
5003	80000000	996600a6
500b

send & receive etc. etc. Most games switch to 0x25 for the server as well after a while.

when you want to exit

0x128 reg	Send	Receive
5003
5083	99660130	80000000
500b
5003
5083	00000001	80000000
500b
5003
5083	80000000	996600b0
500b

Client