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231 lines
16 KiB
Markdown
231 lines
16 KiB
Markdown
# gba-link-connection
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A set of Game Boy Advance (GBA) C++ libraries to interact with the Serial Port. Its main purpose is providing multiplayer support to homebrew games.
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- [👾](#-LinkCable) [LinkCable.h](lib/LinkCable.h): The classic 16-bit **Multi-Play mode** (up to 4 players) using a GBA Link Cable!
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- [💻](#-LinkCableMultiboot) [LinkCableMultiboot.h](lib/LinkCableMultiboot.h): Send **Multiboot software** (small 256KiB ROMs) to other GBAs with no cartridge!
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- [🔌](#-LinkGPIO) [LinkGPIO.h](lib/LinkGPIO.h): Use the Link Port however you want to control **any device** (like LEDs, rumble motors, and that kind of stuff)!
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- [🔗](#-LinkSPI) [LinkSPI.h](lib/LinkSPI.h): Connect with a PC (like a **Raspberry Pi**) or another GBA (with a GBC Link Cable) using this mode. Transfer up to 2Mbit/s!
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- [📻](#-LinkWireless) [LinkWireless.h](lib/LinkWireless.h): Connect up to 5 consoles with the **Wireless Adapter**!
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- [🌎](#-LinkUniversal) [LinkUniversal.h](lib/LinkUniversal.h): Add multiplayer support to you game, both with 👾 *Link Cables* and 📻 *Wireless Adapters*, using the **same API**.
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*(click on the emojis for documentation)*
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> <img alt="rlabs" width="16" height="16" src="https://user-images.githubusercontent.com/1631752/116227197-400d2380-a72a-11eb-9e7b-389aae76f13e.png" /> Created by [[r]labs](https://r-labs.io).
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## Usage
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- Include the library you want (e.g. [LinkCable.h](lib/LinkCable.h)) in your game code, and read its comment for instructions.
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- Check out the [examples](examples) folder
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* Builds are available in *Releases*.
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* They can be tested on real GBAs or using emulators (*NO$GBA*, *mGBA*, or *VBA-M*).
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### Makefile actions (for all examples)
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```bash
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make [ clean | build | start | rebuild | restart ]
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```
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# 👾 LinkCable
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*(aka Multi-Play Mode)*
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This is the Link Port mode that games use for multiplayer.
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The library uses message queues to send/receive data and transmits when it's possible. As it uses CPU interrupts, the connection is alive even if a console drops a frame or gets stucked in a long iteration loop. After such event, all nodes end up receiving all the pending messages, so a lockstep communication protocol can be used.
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## Constructor
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`new LinkCable(...)` accepts these **optional** parameters:
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Name | Type | Default | Description
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--- | --- | --- | ---
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`baudRate` | **BaudRate** | `BAUD_RATE_1` | Sets a specific baud rate.
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`timeout` | **u32** | `3` | Number of *frames* without an `II_SERIAL` IRQ to reset the connection.
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`remoteTimeout` | **u32** | `5` | Number of *messages* with `0xFFFF` to mark a player as disconnected.
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`interval` | **u16** | `50` | Number of *1024cycles* (61.04μs) ticks between messages *(50 = 3.052ms)*. It's the interval of Timer #`sendTimerId`.
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`sendTimerId` | **u8** *(0~3)* | `3` | GBA Timer to use for sending.
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You can also change these compile-time constants:
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- `LINK_CABLE_QUEUE_SIZE`: to set a custom buffer size (how many incoming and outcoming messages the queues can store at max). The default value is `30`, which seems fine for most games.
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## Methods
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Name | Return type | Description
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--- | --- | ---
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`isActive()` | **bool** | Returns whether the library is active or not.
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`activate()` | - | Activates the library.
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`deactivate()` | - | Deactivates the library.
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`isConnected()` | **bool** | Returns `true` if there are at least 2 connected players.
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`playerCount()` | **u8** *(0~4)* | Returns the number of connected players.
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`currentPlayerId()` | **u8** *(0~3)* | Returns the current player id.
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`canRead(playerId)` | **bool** | Returns `true` if there are pending messages from player #`playerId`.
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`read(playerId)` | **u16** | Returns one message from player #`playerId`.
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`consume()` | - | Marks the current data as processed, enabling the library to fetch more.
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`send(data)` | - | Sends `data` to all connected players.
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⚠️ `0xFFFF` and `0x0` are reserved values, so don't send them!
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# 💻 LinkCableMultiboot
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*(aka Multiboot through Multi-Play mode)*
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This tool allows sending Multiboot ROMs (small 256KiB programs that fit in EWRAM) from one GBA to up to 3 slaves, using a single cartridge.
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## Methods
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Name | Return type | Description
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--- | --- | ---
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`sendRom(rom, romSize, cancel)` | **LinkCableMultiboot::Result** | Sends the `rom`. During the handshake process, the library will continuously invoke `cancel`, and abort the transfer if it returns `true`. The `romSize` must be a number between `448` and `262144`, and a multiple of `16`. Once completed, the return value should be `LinkCableMultiboot::Result::SUCCESS`.
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⚠️ for better results, turn on the GBAs **after** calling the `sendRom` method!
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# 🔌 LinkGPIO
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*(aka General Purpose Mode)*
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This is the default Link Port mode, and it allows users to manipulate pins `SI`, `SO`, `SD` and `SC` directly.
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## Methods
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Name | Return type | Description
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--- | --- | ---
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`reset()` | - | Resets communication mode to General Purpose. **Required to initialize the library!**
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`setMode(pin, direction)` | - | Configures a `pin` to use a `direction` (input or output).
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`getMode(pin)` | **LinkGPIO::Direction** | Returns the direction set at `pin`.
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`readPin(pin)` | **bool** | Returns whether a `pin` is *HIGH* or not (when set as an input).
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`writePin(pin, isHigh)` | - | Sets a `pin` to be high or not (when set as an output).
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`setSIInterrupts(isEnabled)` | - | If it `isEnabled`, a IRQ will be generated when `SI` changes from *HIGH* to *LOW*.
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⚠️ always set the `SI` terminal to an input!
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# 🔗 LinkSPI
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*(aka Normal Mode)*
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This is GBA's implementation of SPI. In this library, packets are set to 32-bit, as there's no benefit to using the 8-bit version. You can use this to interact with other GBAs or computers that know SPI.
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## Methods
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Name | Return type | Description
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--- | --- | ---
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`isActive()` | **bool** | Returns whether the library is active or not.
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`activate(mode)` | - | Activates the library in a specific `mode` (one of `LinkSPI::Mode::SLAVE`, `LinkSPI::Mode::MASTER_256KBPS`, or `LinkSPI::Mode::MASTER_2MBPS`).
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`deactivate()` | - | Deactivates the library.
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`transfer(data)` | **u32** | Exchanges `data` with the other end. Returns the received data.
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`transfer(data, cancel)` | **u32** | Like `transfer(data)` but accepts a `cancel()` function. The library will continuously invoke it, and abort the transfer if it returns `true`.
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`transferAsync(data, [cancel])` | - | Schedules a `data` transfer and returns. After this, call `getAsyncState()` and `getAsyncData()`. Note that until you retrieve the async data, normal `transfer(...)`s won't do anything!
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`getAsyncState()` | **LinkSPI::AsyncState** | Returns the state of the last async transfer (one of `LinkSPI::AsyncState::IDLE`, `LinkSPI::AsyncState::WAITING`, or `LinkSPI::AsyncState::READY`).
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`getAsyncData()` | **u32** | If the async state is `READY`, returns the remote data and switches the state back to `IDLE`.
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`getMode()` | **LinkSPI::Mode** | Returns the current `mode`.
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`setWaitModeActive(isActive)` | - | Enables or disables `waitMode` (*).
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`isWaitModeActive()` | **bool** | Returns whether `waitMode` (*) is active or not.
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> (*) `waitMode`: The GBA adds an extra feature over SPI. When working as master, it can check whether the other terminal is ready to receive, and wait if it's not. That makes the connection more reliable, but it's not always supported on other hardware units (e.g. the Wireless Adapter), so it must be disabled in those cases.
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>
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> `waitMode` is disabled by default.
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⚠️ when using Normal Mode between two GBAs, use a GBC Link Cable!
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⚠️ only use the 2Mbps mode with custom hardware (very short wires)!
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⚠️ don't send `0xFFFFFFFF`, it's reserved for errors!
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# 📻 LinkWireless
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*(aka GBA Wireless Adapter)*
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This is a driver for an accessory that enables wireless games up to 5 players. The inner workings of the adapter are highly unknown, but [this article](docs/wireless_adapter.md) is very helpful. I've updated the blog post to add more details about the things I learnt by the means of ~~reverse engineering~~ brute force and trial&error.
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The library, by default, implements a lightweight protocol (on top of the adapter's message system) that sends packet IDs and checksums. This allows detecting disconnections, forwarding messages to all nodes, and retransmitting to prevent packet loss.
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## Constructor
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`new LinkWireless(...)` accepts these **optional** parameters:
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Name | Type | Default | Description
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--- | --- | --- | ---
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`forwarding` | **bool** | `true` | If `true`, the server forwards all messages to the clients. Otherwise, clients only see messages sent from the server (ignoring other peers).
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`retransmission` | **bool** | `true` | If `true`, the library handles retransmission for you, so there should be no packet loss.
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`maxPlayers` | **u8** *(2~5)* | `5` | Maximum number of allowed players. The adapter will accept connections after reaching the limit, but the library will ignore them. If your game only supports -for example- two players, set this to `2` as it will make transfers faster.
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`timeout` | **u32** | `8` | Number of *frames* without receiving *any* data to reset the connection.
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`remoteTimeout` | **u32** | `10` | Number of *successful transfers* without a message from a client to mark the player as disconnected.
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`interval` | **u16** | `50` | Number of *1024cycles* (61.04μs) ticks between transfers *(50 = 3.052ms)*. It's the interval of Timer #`sendTimerId`.
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`sendTimerId` | **u8** *(0~3)* | `3` | GBA Timer to use for sending.
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`asyncACKTimerId` | **s8** *(0~3 or -1)* | `-1` | GBA Timer to use for ACKs. If you have free timers, use one here to reduce CPU usage.
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You can also change these compile-time constants:
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- `LINK_WIRELESS_QUEUE_SIZE`: to set a custom buffer size (how many incoming and outcoming messages the queues can store at max). The default value is `30`, which seems fine for most games.
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- `LINK_WIRELESS_MAX_COMMAND_RESPONSE_LENGTH`: to set the biggest allowed response from the adapter. The default value is `50`, which allows reading all user messages (max receive length is `21`) and -in theory- up to `7` broadcasting servers *(7 values per broadcast * 7 = 49 responses)*. This library was only tested with `4` adapters, so the real maximum is unknown.
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- `LINK_WIRELESS_MAX_SERVER_TRANSFER_LENGTH` and `LINK_WIRELESS_MAX_CLIENT_TRANSFER_LENGTH`: to set the biggest allowed transfer per timer tick. Transfers contain retransmission headers and multiple user messages. These values must be in the range `[6;20]` for servers and `[2;4]` for clients. The default values are `20` and `4`, but you might want to set them a bit lower to reduce CPU usage.
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## Methods
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- Most of these methods return a boolean, indicating if the action was successful. If not, you can call `getLastError()` to know the reason. Usually, unless it's a trivial error (like buffers being full), the connection with the adapter is reset and the game needs to start again.
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- You can check the connection state at any time with `getState()`.
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- Until a session starts, all actions are synchronic.
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- During sessions (when the state is `SERVING` or `CONNECTED`), the message transfers are IRQ-driven, so `send(...)` and `receive(...)` won't waste extra cycles.
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Name | Return type | Description
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--- | --- | ---
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`isActive()` | **bool** | Returns whether the library is active or not.
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`activate()` | **bool** | Activates the library. When an adapter is connected, it changes the state to `AUTHENTICATED`. It can also be used to disconnect or reset the adapter.
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`deactivate()` | - | Deactivates the library.
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`serve([gameName], [userName])` | **bool** | Starts broadcasting a server and changes the state to `SERVING`. You can, optionally, provide a `gameName` (max `14` characters) and `userName` (max `8` characters) that games will be able to read.
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`getServers(servers, [onWait])` | **bool** | Fills the `servers` array with all the currently broadcasting servers. This action takes 1 second to complete, but you can optionally provide an `onWait()` function which will be invoked each time VBlank starts.
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`getServersAsyncStart()` | **bool** | Starts looking for broadcasting servers and changes the state to `SEARCHING`. After this, call `getServersAsyncEnd(...)` 1 second later.
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`getServersAsyncEnd(servers)` | **bool** | Fills the `servers` array with all the currently broadcasting servers. Changes the state to `AUTHENTICATED` again.
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`connect(serverId)` | **bool** | Starts a connection with `serverId` and changes the state to `CONNECTING`.
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`keepConnecting()` | **bool** | When connecting, this needs to be called until the state is `CONNECTED`. It assigns a player id. Keep in mind that `isConnected()` and `playerCount()` won't be updated until the first message from server arrives.
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`send(data)` | **bool** | Enqueues `data` to be sent to other nodes.
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`receive(messages)` | **bool** | Fills the `messages` array with incoming messages, forwarding if needed.
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`getState()` | **LinkWireless::State** | Returns the current state (one of `LinkWireless::State::NEEDS_RESET`, `LinkWireless::State::AUTHENTICATED`, `LinkWireless::State::SEARCHING`, `LinkWireless::State::SERVING`, `LinkWireless::State::CONNECTING`, or `LinkWireless::State::CONNECTED`).
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`isConnected()` | **bool** | Returns true if the player count is higher than 1.
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`isSessionActive()` | **bool** | Returns true if the state is `SERVING` or `CONNECTED`.
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`playerCount()` | **u8** *(1~5)* | Returns the number of connected players.
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`currentPlayerId()` | **u8** *(0~4)* | Returns the current player id.
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`getLastError([clear])` | **LinkWireless::Error** | If one of the other methods returns `false`, you can inspect this to know the cause. After this call, the last error is cleared if `clear` is `true` (default behavior).
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⚠️ `0xFFFF` is a reserved value, so don't send it!
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# 🌎 LinkUniversal
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A multiuse library that doesn't care whether you plug a Link Cable or a Wireless Adapter. It continuously switches between both and try to connect to other peers, supporting hot swapping cables with adapters and all the features from [👾 LinkCable](#-LinkCable) and [📻 LinkWireless](#-LinkWireless).
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https://github.com/afska/gba-link-connection/assets/1631752/b2900110-3b27-4cdb-8ae1-744878d6384b
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## Constructor
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`new LinkUniversal(...)` accepts these **optional** parameters:
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Name | Type | Default | Description
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--- | --- | --- | ---
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`protocol` | **LinkUniversal::Protocol** | `AUTODETECT` | Specifies what protocol should be used (one of `LinkUniversal::Protocol::AUTODETECT`, `LinkUniversal::Protocol::CABLE`, `LinkUniversal::Protocol::WIRELESS_AUTO`, or `LinkUniversal::Protocol::WIRELESS_CLIENT`).
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`gameName` | **std::string** | `""` | The game name that will be broadcasted in wireless sessions. The library uses this to only connect to servers from the same game.
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`cableOptions` | **LinkUniversal::CableOptions** | *same as LinkCable* | All the [👾 LinkCable](#constructor) constructor parameters in one *struct*.
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`wirelessOptions` | **LinkUniversal::WirelessOptions** | *same as LinkWireless* | All the [📻 LinkWireless](#constructor-1) constructor parameters in one *struct*.
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## Methods
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The interface is the same as [👾 LinkCable](#methods), with one exception: instead of calling `consume()` at the end of your game loop, you call `sync()` at the start.
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Aditionally, it supports these methods:
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Name | Return type | Description
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--- | --- | ---
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`getState()` | **LinkUniversal::State** | Returns the current state (one of `LinkUniversal::State::INITIALIZING`, `LinkUniversal::State::WAITING`, or `LinkUniversal::State::CONNECTED`).
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`getMode()` | **LinkUniversal::Mode** | Returns the active mode (one of `LinkUniversal::Mode::LINK_CABLE`, or `LinkUniversal::Mode::LINK_WIRELESS`).
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`getProtocol()` | **LinkUniversal::Protocol** | Returns the active protocol (one of `LinkUniversal::Protocol::AUTODETECT`, `LinkUniversal::Protocol::CABLE`, `LinkUniversal::Protocol::WIRELESS_AUTO`, or `LinkUniversal::Protocol::WIRELESS_CLIENT`).
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`setProtocol(protocol)` | - | Sets the active `protocol`.
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`getWirelessState()` | **LinkWireless::State** | Returns the wireless state (same as [📻 LinkWireless](#methods-4)'s `getState()`).
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