# Maple Reference Documentation: Libraries

This page briefly summarizes the Arduino libraries that have been ported to Maple. You can use a library from within a sketch by going to Sketch > Import Library... from within the IDE, then choosing the library you want.

Any incompatibilities between the Maple and Arduino versions are noted in the description of the library.

- LiquidCrystal
- Wire

## LiquidCrystal

The LiquidCrystal library allows Maple to control LCD screens. For more information, see the Arduino LiquidCrystal documentation.

### Compatibility Note

At this time, no incompatibilities between the Maple and Arduino versions are known. Any observed differences should be considered bugs, and reported on the forums.

## Wire

We provide a soft (bit-banged) implementation of the Wire I2C library.

### Compatibility Note

This implementation is synchronous, and thus supports only a subset of the full Wire interface (however, the functionality which is supported is fully compatible with Arduino). For now, please use the function reference which follows when developing projects using our implementation.

Please note that the current implementation only supports master mode using a bit-banged (software) protocol. Future enhancements will use the hardware i2c peripheral on the stm32 as well as the DMA for performance. Support for slave, smBUS, and multimaster modes are also slated for inclusion in the enhanced Wire port.

### Function Reference

`Wire.begin()`
  Joins the i2c bus as master, using pin 20 as SDA and pin 21 as SCL (this is compatible with the pin settings on the Arduino Mega).
`Wire.begin(sda, scl)`
  Like `Wire.begin()`, but with the given pins as SDA and SCL.
`Wire.beginTransmission(slave_address)`
  Set up a transmission to a slave device with the given 7-bit address. Bytes subsequently queued for transmission (using `Wire.send`) will be sent to `slave_address` when `Wire.endTransmission` is called.
`Wire.send(byte)`
  Queues the given byte (`int` or `uint8`) to the slave address previously specified by a call to `Wire.beginTransmission`. At most 32 bytes may be queued in a single transmission.
`Wire.send(string)`
  Queues a given string (`char*`) for transmission. The characters of the string are individually queued for transmission as bytes. At most 32 bytes may be queued in a single transmission.
`Wire.send(buffer, length)`
  Queues a byte buffer `buffer` (`int*` or `uint8*`), of length `length`, for transmission. At most 32 bytes may be queued in a single transmission.
`Wire.endTransmission()`
  Ends a transmission (begun by `Wire.beginTransmission`), and actually sends the bytes queued by calls to `Wire.send`.

  The return value is one of the following status codes:

  - `SUCCESS`: All bytes were transmitted successfully
  - `EDATA`: More than 32 bytes were queued for transmission. No bytes are actually sent when this happens.
  - `ENACKADDR`: Did not receive ACK on transmit of address. No bytes are actually sent when this happens.
  - `ENACKTRNS`: Did not receive ACK during transmit of data. Some bytes may have been sent when this happens; however, the transmission is aborted after the first byte of data which is not ACKed by the slave device.
  - `EOTHER`: Other error occurred.
`Wire.requestFrom(address, num_bytes)`
  Requests `num_bytes` bytes from 7-bit slave address `address`. Returns the actual number of bytes read. These bytes may subsequently be read one at a time using `Wire.receive()`.

  Note: if `num_bytes` exceeds the size of the transmit/receive buffer (currently 32), it will be truncated to 32.

`Wire.receive()`
  Get the next byte read during the previous call to `Wire.requestFrom`. You can check how many bytes are left to read using `Wire.available()`.
`Wire.available()`
  Returns the number of bytes which are still available for reading from the last call to `Wire.requestFrom`.