diff options
Diffstat (limited to 'source/libs')
| -rw-r--r-- | source/libs/servo.rst | 59 | ||||
| -rw-r--r-- | source/libs/wire.rst | 104 |
2 files changed, 159 insertions, 4 deletions
diff --git a/source/libs/servo.rst b/source/libs/servo.rst index 475f7dd..891f151 100644 --- a/source/libs/servo.rst +++ b/source/libs/servo.rst @@ -2,9 +2,8 @@ .. _libs-servo: -======= - Servo -======= +Servo +===== .. FIXME [0.0.10] this is out of date @@ -16,7 +15,8 @@ You can use this library in the :ref:`IDE <ide>` by choosing the Servo item under the Sketch > Import Library... menu. If you are using the :ref:`Unix toolchain <unix-toolchain>`, the -library is located in ``$LIB_MAPLE_HOME/libraries/Servo/``. +library is located in the ``/libraries/Servo/`` :ref:`libmaple` +directory. Servo Class Reference --------------------- @@ -108,3 +108,54 @@ servomotor attached to pin 9, you could write :: microseconds. This will be clamped to lie in the [``min``, ``max``\ ] pulse width range set during :ref:`attach() <libs-servo-attach>`. + +Arduino Compatibility +--------------------- + +The Servo class provides a public interface identical to the Arduino +version's documented functionality (as of Arduino 0021), so in most +cases, this library will be a drop-in replacement. + +However, there are some differences, essentially at the level of +implementation details. + +The major difference is that while the Arduino implementation drives +the servos with "bit-banged" :ref:`PWM <pwm>`, the Maple +implementation uses :ref:`timers <timers>` to drive the PWM directly. + +Consequently, **the Maple implementation only allows Servo instances +to** :ref:`attach <libs-servo-attach>` **to pins that support PWM**. + +To determine if a pin supports PWM (15 Maple pins do), you can either +check if "PWM" appears next to its number on the Maple silkscreen, or +consult the :ref:`pwmWrite() <lang-pwmwrite>` documentation. + +RC Servos expect a pulse approximately every 20ms. In the Maple +implementation, :ref:`periods <lang-hardwaretimer-setperiod>` are set +for entire timers, rather than individual channels. Thus, +``attach()``\ ing a Servo to a pin can interfere with other pins +associated with the same timer\ [#fard-servo]_. + +Because of this, we recommend connecting multiple servomotors to pins +which share a timer, in order to keep as many timers free for other +purposes as possible. Consult your board's :ref:`Timer Pin Map +<gpio-pin-maps>` to match up pins and timer channels. + +Another difference: although it is not publicly documented to do so, +the Arduino implementation of `attach() +<http://arduino.cc/en/Reference/ServoAttach>`_ returns the timer +channel associated with the newly-attached pin, or 0 on failure (as of +Arduino 0021). The Maple implementation returns :ref:`true +<lang-constants-true>` on success, and :ref:`false +<lang-constants-false>` on failure (and this is its documented +behavior). + +We currently provide a soft (bit-banged) implementation of the +:ref:`Wire <libs-wire>` I2C library. + +.. rubric:: Footnotes + +.. [#fard-servo] The Arduino implementation also captures timer + channels in groups as more Servo objects are attached, but the + details of which channels have their periods reset when are + slightly different. 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`. + + |