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diff --git a/source/libs/wire.rst b/source/libs/wire.rst new file mode 100644 index 0000000..2c5bed9 --- /dev/null +++ b/source/libs/wire.rst @@ -0,0 +1,104 @@ +.. highlight:: cpp + +.. _libs-wire: + +Wire +==== + +.. TODO [0.1.0] Format this correctly, using Breathe + +This page documents the Wire library for the :ref:`i2c` protocol. You +can use this library in the :ref:`Maple IDE <ide>` by choosing the +Wire item under the Sketch > Import Library... menu. + +If you are using the :ref:`Unix toolchain <unix-toolchain>`, the +library is located in the ``/libraries/Wire/`` :ref:`libmaple` +directory. + +Wire 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 ``void + Wire.endTransmission()`` is called. + +``void Wire.send(byte)`` + Queues the given byte (``uint8`` or ``int``) 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`` (``uint8*`` or ``int*``), with + ``length`` elements, for transmission. At most 32 bytes may be + queued in a single transmission. + +``Wire.endTransmission()`` + Ends a transmission (begun by ``Wire.beginTransmission(uint8)``), + 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 and return the next byte read during the previous call to + ``Wire.requestFrom(uint8, int)``. You can check how many bytes are + left to read using ``uint8 Wire.available()``. + +``Wire.available()`` + Returns the number of bytes which are still available for reading + (with ``Wire.receive()``) from the last call to + ``Wire.requestFrom(uint8, int)``. + +Arduino Compatibility +--------------------- + +.. FIXME [0.1.0] Replace this section when i2c Wire wrapper is done + +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. For now, use of the hardware +:ref:`i2c` peripheral is only available through :ref:`libmaple-i2c`. + + |